root / htools / Ganeti / THH.hs @ 9b156883
History | View | Annotate | Download (37.8 kB)
1 |
{-# LANGUAGE TemplateHaskell #-} |
---|---|
2 |
|
3 |
{-| TemplateHaskell helper for Ganeti Haskell code. |
4 |
|
5 |
As TemplateHaskell require that splices be defined in a separate |
6 |
module, we combine all the TemplateHaskell functionality that HTools |
7 |
needs in this module (except the one for unittests). |
8 |
|
9 |
-} |
10 |
|
11 |
{- |
12 |
|
13 |
Copyright (C) 2011, 2012 Google Inc. |
14 |
|
15 |
This program is free software; you can redistribute it and/or modify |
16 |
it under the terms of the GNU General Public License as published by |
17 |
the Free Software Foundation; either version 2 of the License, or |
18 |
(at your option) any later version. |
19 |
|
20 |
This program is distributed in the hope that it will be useful, but |
21 |
WITHOUT ANY WARRANTY; without even the implied warranty of |
22 |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
23 |
General Public License for more details. |
24 |
|
25 |
You should have received a copy of the GNU General Public License |
26 |
along with this program; if not, write to the Free Software |
27 |
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
28 |
02110-1301, USA. |
29 |
|
30 |
-} |
31 |
|
32 |
module Ganeti.THH ( declareSADT |
33 |
, declareIADT |
34 |
, makeJSONInstance |
35 |
, genOpID |
36 |
, genAllOpIDs |
37 |
, genOpCode |
38 |
, genStrOfOp |
39 |
, genStrOfKey |
40 |
, genLuxiOp |
41 |
, Field |
42 |
, simpleField |
43 |
, defaultField |
44 |
, optionalField |
45 |
, optionalNullSerField |
46 |
, renameField |
47 |
, customField |
48 |
, timeStampFields |
49 |
, uuidFields |
50 |
, serialFields |
51 |
, tagsFields |
52 |
, TagSet |
53 |
, buildObject |
54 |
, buildObjectSerialisation |
55 |
, buildParam |
56 |
, DictObject(..) |
57 |
, genException |
58 |
, excErrMsg |
59 |
) where |
60 |
|
61 |
import Control.Monad (liftM) |
62 |
import Data.Char |
63 |
import Data.List |
64 |
import Data.Maybe (fromMaybe) |
65 |
import qualified Data.Set as Set |
66 |
import Language.Haskell.TH |
67 |
|
68 |
import qualified Text.JSON as JSON |
69 |
import Text.JSON.Pretty (pp_value) |
70 |
|
71 |
-- * Exported types |
72 |
|
73 |
-- | Class of objects that can be converted to 'JSObject' |
74 |
-- lists-format. |
75 |
class DictObject a where |
76 |
toDict :: a -> [(String, JSON.JSValue)] |
77 |
|
78 |
-- | Optional field information. |
79 |
data OptionalType |
80 |
= NotOptional -- ^ Field is not optional |
81 |
| OptionalOmitNull -- ^ Field is optional, null is not serialised |
82 |
| OptionalSerializeNull -- ^ Field is optional, null is serialised |
83 |
deriving (Show, Eq) |
84 |
|
85 |
-- | Serialised field data type. |
86 |
data Field = Field { fieldName :: String |
87 |
, fieldType :: Q Type |
88 |
, fieldRead :: Maybe (Q Exp) |
89 |
, fieldShow :: Maybe (Q Exp) |
90 |
, fieldDefault :: Maybe (Q Exp) |
91 |
, fieldConstr :: Maybe String |
92 |
, fieldIsOptional :: OptionalType |
93 |
} |
94 |
|
95 |
-- | Generates a simple field. |
96 |
simpleField :: String -> Q Type -> Field |
97 |
simpleField fname ftype = |
98 |
Field { fieldName = fname |
99 |
, fieldType = ftype |
100 |
, fieldRead = Nothing |
101 |
, fieldShow = Nothing |
102 |
, fieldDefault = Nothing |
103 |
, fieldConstr = Nothing |
104 |
, fieldIsOptional = NotOptional |
105 |
} |
106 |
|
107 |
-- | Sets the renamed constructor field. |
108 |
renameField :: String -> Field -> Field |
109 |
renameField constrName field = field { fieldConstr = Just constrName } |
110 |
|
111 |
-- | Sets the default value on a field (makes it optional with a |
112 |
-- default value). |
113 |
defaultField :: Q Exp -> Field -> Field |
114 |
defaultField defval field = field { fieldDefault = Just defval } |
115 |
|
116 |
-- | Marks a field optional (turning its base type into a Maybe). |
117 |
optionalField :: Field -> Field |
118 |
optionalField field = field { fieldIsOptional = OptionalOmitNull } |
119 |
|
120 |
-- | Marks a field optional (turning its base type into a Maybe), but |
121 |
-- with 'Nothing' serialised explicitly as /null/. |
122 |
optionalNullSerField :: Field -> Field |
123 |
optionalNullSerField field = field { fieldIsOptional = OptionalSerializeNull } |
124 |
|
125 |
-- | Sets custom functions on a field. |
126 |
customField :: Name -- ^ The name of the read function |
127 |
-> Name -- ^ The name of the show function |
128 |
-> Field -- ^ The original field |
129 |
-> Field -- ^ Updated field |
130 |
customField readfn showfn field = |
131 |
field { fieldRead = Just (varE readfn), fieldShow = Just (varE showfn) } |
132 |
|
133 |
-- | Computes the record name for a given field, based on either the |
134 |
-- string value in the JSON serialisation or the custom named if any |
135 |
-- exists. |
136 |
fieldRecordName :: Field -> String |
137 |
fieldRecordName (Field { fieldName = name, fieldConstr = alias }) = |
138 |
fromMaybe (camelCase name) alias |
139 |
|
140 |
-- | Computes the preferred variable name to use for the value of this |
141 |
-- field. If the field has a specific constructor name, then we use a |
142 |
-- first-letter-lowercased version of that; otherwise, we simply use |
143 |
-- the field name. See also 'fieldRecordName'. |
144 |
fieldVariable :: Field -> String |
145 |
fieldVariable f = |
146 |
case (fieldConstr f) of |
147 |
Just name -> ensureLower name |
148 |
_ -> map (\c -> if c == '-' then '_' else c) $ fieldName f |
149 |
|
150 |
-- | Compute the actual field type (taking into account possible |
151 |
-- optional status). |
152 |
actualFieldType :: Field -> Q Type |
153 |
actualFieldType f | fieldIsOptional f /= NotOptional = [t| Maybe $t |] |
154 |
| otherwise = t |
155 |
where t = fieldType f |
156 |
|
157 |
-- | Checks that a given field is not optional (for object types or |
158 |
-- fields which should not allow this case). |
159 |
checkNonOptDef :: (Monad m) => Field -> m () |
160 |
checkNonOptDef (Field { fieldIsOptional = OptionalOmitNull |
161 |
, fieldName = name }) = |
162 |
fail $ "Optional field " ++ name ++ " used in parameter declaration" |
163 |
checkNonOptDef (Field { fieldIsOptional = OptionalSerializeNull |
164 |
, fieldName = name }) = |
165 |
fail $ "Optional field " ++ name ++ " used in parameter declaration" |
166 |
checkNonOptDef (Field { fieldDefault = (Just _), fieldName = name }) = |
167 |
fail $ "Default field " ++ name ++ " used in parameter declaration" |
168 |
checkNonOptDef _ = return () |
169 |
|
170 |
-- | Produces the expression that will de-serialise a given |
171 |
-- field. Since some custom parsing functions might need to use the |
172 |
-- entire object, we do take and pass the object to any custom read |
173 |
-- functions. |
174 |
loadFn :: Field -- ^ The field definition |
175 |
-> Q Exp -- ^ The value of the field as existing in the JSON message |
176 |
-> Q Exp -- ^ The entire object in JSON object format |
177 |
-> Q Exp -- ^ Resulting expression |
178 |
loadFn (Field { fieldRead = Just readfn }) expr o = [| $expr >>= $readfn $o |] |
179 |
loadFn _ expr _ = expr |
180 |
|
181 |
-- * Common field declarations |
182 |
|
183 |
-- | Timestamp fields description. |
184 |
timeStampFields :: [Field] |
185 |
timeStampFields = |
186 |
[ defaultField [| 0::Double |] $ simpleField "ctime" [t| Double |] |
187 |
, defaultField [| 0::Double |] $ simpleField "mtime" [t| Double |] |
188 |
] |
189 |
|
190 |
-- | Serial number fields description. |
191 |
serialFields :: [Field] |
192 |
serialFields = |
193 |
[ renameField "Serial" $ simpleField "serial_no" [t| Int |] ] |
194 |
|
195 |
-- | UUID fields description. |
196 |
uuidFields :: [Field] |
197 |
uuidFields = [ simpleField "uuid" [t| String |] ] |
198 |
|
199 |
-- | Tag set type alias. |
200 |
type TagSet = Set.Set String |
201 |
|
202 |
-- | Tag field description. |
203 |
tagsFields :: [Field] |
204 |
tagsFields = [ defaultField [| Set.empty |] $ |
205 |
simpleField "tags" [t| TagSet |] ] |
206 |
|
207 |
-- * Internal types |
208 |
|
209 |
-- | A simple field, in constrast to the customisable 'Field' type. |
210 |
type SimpleField = (String, Q Type) |
211 |
|
212 |
-- | A definition for a single constructor for a simple object. |
213 |
type SimpleConstructor = (String, [SimpleField]) |
214 |
|
215 |
-- | A definition for ADTs with simple fields. |
216 |
type SimpleObject = [SimpleConstructor] |
217 |
|
218 |
-- * Helper functions |
219 |
|
220 |
-- | Ensure first letter is lowercase. |
221 |
-- |
222 |
-- Used to convert type name to function prefix, e.g. in @data Aa -> |
223 |
-- aaToRaw@. |
224 |
ensureLower :: String -> String |
225 |
ensureLower [] = [] |
226 |
ensureLower (x:xs) = toLower x:xs |
227 |
|
228 |
-- | Ensure first letter is uppercase. |
229 |
-- |
230 |
-- Used to convert constructor name to component |
231 |
ensureUpper :: String -> String |
232 |
ensureUpper [] = [] |
233 |
ensureUpper (x:xs) = toUpper x:xs |
234 |
|
235 |
-- | Helper for quoted expressions. |
236 |
varNameE :: String -> Q Exp |
237 |
varNameE = varE . mkName |
238 |
|
239 |
-- | showJSON as an expression, for reuse. |
240 |
showJSONE :: Q Exp |
241 |
showJSONE = varNameE "showJSON" |
242 |
|
243 |
-- | ToRaw function name. |
244 |
toRawName :: String -> Name |
245 |
toRawName = mkName . (++ "ToRaw") . ensureLower |
246 |
|
247 |
-- | FromRaw function name. |
248 |
fromRawName :: String -> Name |
249 |
fromRawName = mkName . (++ "FromRaw") . ensureLower |
250 |
|
251 |
-- | Converts a name to it's varE\/litE representations. |
252 |
reprE :: Either String Name -> Q Exp |
253 |
reprE = either stringE varE |
254 |
|
255 |
-- | Smarter function application. |
256 |
-- |
257 |
-- This does simply f x, except that if is 'id', it will skip it, in |
258 |
-- order to generate more readable code when using -ddump-splices. |
259 |
appFn :: Exp -> Exp -> Exp |
260 |
appFn f x | f == VarE 'id = x |
261 |
| otherwise = AppE f x |
262 |
|
263 |
-- | Builds a field for a normal constructor. |
264 |
buildConsField :: Q Type -> StrictTypeQ |
265 |
buildConsField ftype = do |
266 |
ftype' <- ftype |
267 |
return (NotStrict, ftype') |
268 |
|
269 |
-- | Builds a constructor based on a simple definition (not field-based). |
270 |
buildSimpleCons :: Name -> SimpleObject -> Q Dec |
271 |
buildSimpleCons tname cons = do |
272 |
decl_d <- mapM (\(cname, fields) -> do |
273 |
fields' <- mapM (buildConsField . snd) fields |
274 |
return $ NormalC (mkName cname) fields') cons |
275 |
return $ DataD [] tname [] decl_d [''Show, ''Read, ''Eq] |
276 |
|
277 |
-- | Generate the save function for a given type. |
278 |
genSaveSimpleObj :: Name -- ^ Object type |
279 |
-> String -- ^ Function name |
280 |
-> SimpleObject -- ^ Object definition |
281 |
-> (SimpleConstructor -> Q Clause) -- ^ Constructor save fn |
282 |
-> Q (Dec, Dec) |
283 |
genSaveSimpleObj tname sname opdefs fn = do |
284 |
let sigt = AppT (AppT ArrowT (ConT tname)) (ConT ''JSON.JSValue) |
285 |
fname = mkName sname |
286 |
cclauses <- mapM fn opdefs |
287 |
return $ (SigD fname sigt, FunD fname cclauses) |
288 |
|
289 |
-- * Template code for simple raw type-equivalent ADTs |
290 |
|
291 |
-- | Generates a data type declaration. |
292 |
-- |
293 |
-- The type will have a fixed list of instances. |
294 |
strADTDecl :: Name -> [String] -> Dec |
295 |
strADTDecl name constructors = |
296 |
DataD [] name [] |
297 |
(map (flip NormalC [] . mkName) constructors) |
298 |
[''Show, ''Read, ''Eq, ''Enum, ''Bounded, ''Ord] |
299 |
|
300 |
-- | Generates a toRaw function. |
301 |
-- |
302 |
-- This generates a simple function of the form: |
303 |
-- |
304 |
-- @ |
305 |
-- nameToRaw :: Name -> /traw/ |
306 |
-- nameToRaw Cons1 = var1 |
307 |
-- nameToRaw Cons2 = \"value2\" |
308 |
-- @ |
309 |
genToRaw :: Name -> Name -> Name -> [(String, Either String Name)] -> Q [Dec] |
310 |
genToRaw traw fname tname constructors = do |
311 |
let sigt = AppT (AppT ArrowT (ConT tname)) (ConT traw) |
312 |
-- the body clauses, matching on the constructor and returning the |
313 |
-- raw value |
314 |
clauses <- mapM (\(c, v) -> clause [recP (mkName c) []] |
315 |
(normalB (reprE v)) []) constructors |
316 |
return [SigD fname sigt, FunD fname clauses] |
317 |
|
318 |
-- | Generates a fromRaw function. |
319 |
-- |
320 |
-- The function generated is monadic and can fail parsing the |
321 |
-- raw value. It is of the form: |
322 |
-- |
323 |
-- @ |
324 |
-- nameFromRaw :: (Monad m) => /traw/ -> m Name |
325 |
-- nameFromRaw s | s == var1 = Cons1 |
326 |
-- | s == \"value2\" = Cons2 |
327 |
-- | otherwise = fail /.../ |
328 |
-- @ |
329 |
genFromRaw :: Name -> Name -> Name -> [(String, Name)] -> Q [Dec] |
330 |
genFromRaw traw fname tname constructors = do |
331 |
-- signature of form (Monad m) => String -> m $name |
332 |
sigt <- [t| (Monad m) => $(conT traw) -> m $(conT tname) |] |
333 |
-- clauses for a guarded pattern |
334 |
let varp = mkName "s" |
335 |
varpe = varE varp |
336 |
clauses <- mapM (\(c, v) -> do |
337 |
-- the clause match condition |
338 |
g <- normalG [| $varpe == $(varE v) |] |
339 |
-- the clause result |
340 |
r <- [| return $(conE (mkName c)) |] |
341 |
return (g, r)) constructors |
342 |
-- the otherwise clause (fallback) |
343 |
oth_clause <- do |
344 |
g <- normalG [| otherwise |] |
345 |
r <- [|fail ("Invalid string value for type " ++ |
346 |
$(litE (stringL (nameBase tname))) ++ ": " ++ show $varpe) |] |
347 |
return (g, r) |
348 |
let fun = FunD fname [Clause [VarP varp] |
349 |
(GuardedB (clauses++[oth_clause])) []] |
350 |
return [SigD fname sigt, fun] |
351 |
|
352 |
-- | Generates a data type from a given raw format. |
353 |
-- |
354 |
-- The format is expected to multiline. The first line contains the |
355 |
-- type name, and the rest of the lines must contain two words: the |
356 |
-- constructor name and then the string representation of the |
357 |
-- respective constructor. |
358 |
-- |
359 |
-- The function will generate the data type declaration, and then two |
360 |
-- functions: |
361 |
-- |
362 |
-- * /name/ToRaw, which converts the type to a raw type |
363 |
-- |
364 |
-- * /name/FromRaw, which (monadically) converts from a raw type to the type |
365 |
-- |
366 |
-- Note that this is basically just a custom show\/read instance, |
367 |
-- nothing else. |
368 |
declareADT :: Name -> String -> [(String, Name)] -> Q [Dec] |
369 |
declareADT traw sname cons = do |
370 |
let name = mkName sname |
371 |
ddecl = strADTDecl name (map fst cons) |
372 |
-- process cons in the format expected by genToRaw |
373 |
cons' = map (\(a, b) -> (a, Right b)) cons |
374 |
toraw <- genToRaw traw (toRawName sname) name cons' |
375 |
fromraw <- genFromRaw traw (fromRawName sname) name cons |
376 |
return $ ddecl:toraw ++ fromraw |
377 |
|
378 |
declareIADT :: String -> [(String, Name)] -> Q [Dec] |
379 |
declareIADT = declareADT ''Int |
380 |
|
381 |
declareSADT :: String -> [(String, Name)] -> Q [Dec] |
382 |
declareSADT = declareADT ''String |
383 |
|
384 |
-- | Creates the showJSON member of a JSON instance declaration. |
385 |
-- |
386 |
-- This will create what is the equivalent of: |
387 |
-- |
388 |
-- @ |
389 |
-- showJSON = showJSON . /name/ToRaw |
390 |
-- @ |
391 |
-- |
392 |
-- in an instance JSON /name/ declaration |
393 |
genShowJSON :: String -> Q Dec |
394 |
genShowJSON name = do |
395 |
body <- [| JSON.showJSON . $(varE (toRawName name)) |] |
396 |
return $ FunD (mkName "showJSON") [Clause [] (NormalB body) []] |
397 |
|
398 |
-- | Creates the readJSON member of a JSON instance declaration. |
399 |
-- |
400 |
-- This will create what is the equivalent of: |
401 |
-- |
402 |
-- @ |
403 |
-- readJSON s = case readJSON s of |
404 |
-- Ok s' -> /name/FromRaw s' |
405 |
-- Error e -> Error /description/ |
406 |
-- @ |
407 |
-- |
408 |
-- in an instance JSON /name/ declaration |
409 |
genReadJSON :: String -> Q Dec |
410 |
genReadJSON name = do |
411 |
let s = mkName "s" |
412 |
body <- [| case JSON.readJSON $(varE s) of |
413 |
JSON.Ok s' -> $(varE (fromRawName name)) s' |
414 |
JSON.Error e -> |
415 |
JSON.Error $ "Can't parse raw value for type " ++ |
416 |
$(stringE name) ++ ": " ++ e ++ " from " ++ |
417 |
show $(varE s) |
418 |
|] |
419 |
return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []] |
420 |
|
421 |
-- | Generates a JSON instance for a given type. |
422 |
-- |
423 |
-- This assumes that the /name/ToRaw and /name/FromRaw functions |
424 |
-- have been defined as by the 'declareSADT' function. |
425 |
makeJSONInstance :: Name -> Q [Dec] |
426 |
makeJSONInstance name = do |
427 |
let base = nameBase name |
428 |
showJ <- genShowJSON base |
429 |
readJ <- genReadJSON base |
430 |
return [InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) [readJ,showJ]] |
431 |
|
432 |
-- * Template code for opcodes |
433 |
|
434 |
-- | Transforms a CamelCase string into an_underscore_based_one. |
435 |
deCamelCase :: String -> String |
436 |
deCamelCase = |
437 |
intercalate "_" . map (map toUpper) . groupBy (\_ b -> not $ isUpper b) |
438 |
|
439 |
-- | Transform an underscore_name into a CamelCase one. |
440 |
camelCase :: String -> String |
441 |
camelCase = concatMap (ensureUpper . drop 1) . |
442 |
groupBy (\_ b -> b /= '_' && b /= '-') . ('_':) |
443 |
|
444 |
-- | Computes the name of a given constructor. |
445 |
constructorName :: Con -> Q Name |
446 |
constructorName (NormalC name _) = return name |
447 |
constructorName (RecC name _) = return name |
448 |
constructorName x = fail $ "Unhandled constructor " ++ show x |
449 |
|
450 |
-- | Extract all constructor names from a given type. |
451 |
reifyConsNames :: Name -> Q [String] |
452 |
reifyConsNames name = do |
453 |
reify_result <- reify name |
454 |
case reify_result of |
455 |
TyConI (DataD _ _ _ cons _) -> mapM (liftM nameBase . constructorName) cons |
456 |
o -> fail $ "Unhandled name passed to reifyConsNames, expected\ |
457 |
\ type constructor but got '" ++ show o ++ "'" |
458 |
|
459 |
-- | Builds the generic constructor-to-string function. |
460 |
-- |
461 |
-- This generates a simple function of the following form: |
462 |
-- |
463 |
-- @ |
464 |
-- fname (ConStructorOne {}) = trans_fun("ConStructorOne") |
465 |
-- fname (ConStructorTwo {}) = trans_fun("ConStructorTwo") |
466 |
-- @ |
467 |
-- |
468 |
-- This builds a custom list of name\/string pairs and then uses |
469 |
-- 'genToRaw' to actually generate the function. |
470 |
genConstrToStr :: (String -> String) -> Name -> String -> Q [Dec] |
471 |
genConstrToStr trans_fun name fname = do |
472 |
cnames <- reifyConsNames name |
473 |
let svalues = map (Left . trans_fun) cnames |
474 |
genToRaw ''String (mkName fname) name $ zip cnames svalues |
475 |
|
476 |
-- | Constructor-to-string for OpCode. |
477 |
genOpID :: Name -> String -> Q [Dec] |
478 |
genOpID = genConstrToStr deCamelCase |
479 |
|
480 |
-- | Builds a list with all defined constructor names for a type. |
481 |
-- |
482 |
-- @ |
483 |
-- vstr :: String |
484 |
-- vstr = [...] |
485 |
-- @ |
486 |
-- |
487 |
-- Where the actual values of the string are the constructor names |
488 |
-- mapped via @trans_fun@. |
489 |
genAllConstr :: (String -> String) -> Name -> String -> Q [Dec] |
490 |
genAllConstr trans_fun name vstr = do |
491 |
cnames <- reifyConsNames name |
492 |
let svalues = sort $ map trans_fun cnames |
493 |
vname = mkName vstr |
494 |
sig = SigD vname (AppT ListT (ConT ''String)) |
495 |
body = NormalB (ListE (map (LitE . StringL) svalues)) |
496 |
return $ [sig, ValD (VarP vname) body []] |
497 |
|
498 |
-- | Generates a list of all defined opcode IDs. |
499 |
genAllOpIDs :: Name -> String -> Q [Dec] |
500 |
genAllOpIDs = genAllConstr deCamelCase |
501 |
|
502 |
-- | OpCode parameter (field) type. |
503 |
type OpParam = (String, Q Type, Q Exp) |
504 |
|
505 |
-- | Generates the OpCode data type. |
506 |
-- |
507 |
-- This takes an opcode logical definition, and builds both the |
508 |
-- datatype and the JSON serialisation out of it. We can't use a |
509 |
-- generic serialisation since we need to be compatible with Ganeti's |
510 |
-- own, so we have a few quirks to work around. |
511 |
genOpCode :: String -- ^ Type name to use |
512 |
-> [(String, [Field])] -- ^ Constructor name and parameters |
513 |
-> Q [Dec] |
514 |
genOpCode name cons = do |
515 |
decl_d <- mapM (\(cname, fields) -> do |
516 |
-- we only need the type of the field, without Q |
517 |
fields' <- mapM actualFieldType fields |
518 |
let fields'' = zip (repeat NotStrict) fields' |
519 |
return $ NormalC (mkName cname) fields'') |
520 |
cons |
521 |
let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq] |
522 |
|
523 |
(savesig, savefn) <- genSaveOpCode cons |
524 |
(loadsig, loadfn) <- genLoadOpCode cons |
525 |
return [declD, loadsig, loadfn, savesig, savefn] |
526 |
|
527 |
-- | Generates the \"save\" clause for an entire opcode constructor. |
528 |
-- |
529 |
-- This matches the opcode with variables named the same as the |
530 |
-- constructor fields (just so that the spliced in code looks nicer), |
531 |
-- and passes those name plus the parameter definition to 'saveObjectField'. |
532 |
saveConstructor :: String -- ^ The constructor name |
533 |
-> [Field] -- ^ The parameter definitions for this |
534 |
-- constructor |
535 |
-> Q Clause -- ^ Resulting clause |
536 |
saveConstructor sname fields = do |
537 |
let cname = mkName sname |
538 |
fnames <- mapM (newName . fieldVariable) fields |
539 |
let pat = conP cname (map varP fnames) |
540 |
let felems = map (uncurry saveObjectField) (zip fnames fields) |
541 |
-- now build the OP_ID serialisation |
542 |
opid = [| [( $(stringE "OP_ID"), |
543 |
JSON.showJSON $(stringE . deCamelCase $ sname) )] |] |
544 |
flist = listE (opid:felems) |
545 |
-- and finally convert all this to a json object |
546 |
flist' = [| $(varNameE "makeObj") (concat $flist) |] |
547 |
clause [pat] (normalB flist') [] |
548 |
|
549 |
-- | Generates the main save opcode function. |
550 |
-- |
551 |
-- This builds a per-constructor match clause that contains the |
552 |
-- respective constructor-serialisation code. |
553 |
genSaveOpCode :: [(String, [Field])] -> Q (Dec, Dec) |
554 |
genSaveOpCode opdefs = do |
555 |
cclauses <- mapM (uncurry saveConstructor) opdefs |
556 |
let fname = mkName "saveOpCode" |
557 |
sigt <- [t| $(conT (mkName "OpCode")) -> JSON.JSValue |] |
558 |
return $ (SigD fname sigt, FunD fname cclauses) |
559 |
|
560 |
-- | Generates load code for a single constructor of the opcode data type. |
561 |
loadConstructor :: String -> [Field] -> Q Exp |
562 |
loadConstructor sname fields = do |
563 |
let name = mkName sname |
564 |
fbinds <- mapM loadObjectField fields |
565 |
let (fnames, fstmts) = unzip fbinds |
566 |
let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames |
567 |
fstmts' = fstmts ++ [NoBindS (AppE (VarE 'return) cval)] |
568 |
return $ DoE fstmts' |
569 |
|
570 |
-- | Generates the loadOpCode function. |
571 |
genLoadOpCode :: [(String, [Field])] -> Q (Dec, Dec) |
572 |
genLoadOpCode opdefs = do |
573 |
let fname = mkName "loadOpCode" |
574 |
arg1 = mkName "v" |
575 |
objname = mkName "o" |
576 |
opid = mkName "op_id" |
577 |
st1 <- bindS (varP objname) [| liftM JSON.fromJSObject |
578 |
(JSON.readJSON $(varE arg1)) |] |
579 |
st2 <- bindS (varP opid) [| $(varNameE "fromObj") |
580 |
$(varE objname) $(stringE "OP_ID") |] |
581 |
-- the match results (per-constructor blocks) |
582 |
mexps <- mapM (uncurry loadConstructor) opdefs |
583 |
fails <- [| fail $ "Unknown opcode " ++ $(varE opid) |] |
584 |
let mpats = map (\(me, c) -> |
585 |
let mp = LitP . StringL . deCamelCase . fst $ c |
586 |
in Match mp (NormalB me) [] |
587 |
) $ zip mexps opdefs |
588 |
defmatch = Match WildP (NormalB fails) [] |
589 |
cst = NoBindS $ CaseE (VarE opid) $ mpats++[defmatch] |
590 |
body = DoE [st1, st2, cst] |
591 |
sigt <- [t| JSON.JSValue -> JSON.Result $(conT (mkName "OpCode")) |] |
592 |
return $ (SigD fname sigt, FunD fname [Clause [VarP arg1] (NormalB body) []]) |
593 |
|
594 |
-- * Template code for luxi |
595 |
|
596 |
-- | Constructor-to-string for LuxiOp. |
597 |
genStrOfOp :: Name -> String -> Q [Dec] |
598 |
genStrOfOp = genConstrToStr id |
599 |
|
600 |
-- | Constructor-to-string for MsgKeys. |
601 |
genStrOfKey :: Name -> String -> Q [Dec] |
602 |
genStrOfKey = genConstrToStr ensureLower |
603 |
|
604 |
-- | Generates the LuxiOp data type. |
605 |
-- |
606 |
-- This takes a Luxi operation definition and builds both the |
607 |
-- datatype and the function trnasforming the arguments to JSON. |
608 |
-- We can't use anything less generic, because the way different |
609 |
-- operations are serialized differs on both parameter- and top-level. |
610 |
-- |
611 |
-- There are two things to be defined for each parameter: |
612 |
-- |
613 |
-- * name |
614 |
-- |
615 |
-- * type |
616 |
-- |
617 |
genLuxiOp :: String -> SimpleObject -> Q [Dec] |
618 |
genLuxiOp name cons = do |
619 |
let tname = mkName name |
620 |
declD <- buildSimpleCons tname cons |
621 |
(savesig, savefn) <- genSaveSimpleObj tname "opToArgs" |
622 |
cons saveLuxiConstructor |
623 |
req_defs <- declareSADT "LuxiReq" . |
624 |
map (\(str, _) -> ("Req" ++ str, mkName ("luxiReq" ++ str))) $ |
625 |
cons |
626 |
return $ [declD, savesig, savefn] ++ req_defs |
627 |
|
628 |
-- | Generates the \"save\" expression for a single luxi parameter. |
629 |
saveLuxiField :: Name -> SimpleField -> Q Exp |
630 |
saveLuxiField fvar (_, qt) = |
631 |
[| JSON.showJSON $(varE fvar) |] |
632 |
|
633 |
-- | Generates the \"save\" clause for entire LuxiOp constructor. |
634 |
saveLuxiConstructor :: SimpleConstructor -> Q Clause |
635 |
saveLuxiConstructor (sname, fields) = do |
636 |
let cname = mkName sname |
637 |
fnames = map (mkName . fst) fields |
638 |
pat = conP cname (map varP fnames) |
639 |
flist = map (uncurry saveLuxiField) (zip fnames fields) |
640 |
finval = if null flist |
641 |
then [| JSON.showJSON () |] |
642 |
else [| JSON.showJSON $(listE flist) |] |
643 |
clause [pat] (normalB finval) [] |
644 |
|
645 |
-- * "Objects" functionality |
646 |
|
647 |
-- | Extract the field's declaration from a Field structure. |
648 |
fieldTypeInfo :: String -> Field -> Q (Name, Strict, Type) |
649 |
fieldTypeInfo field_pfx fd = do |
650 |
t <- actualFieldType fd |
651 |
let n = mkName . (field_pfx ++) . fieldRecordName $ fd |
652 |
return (n, NotStrict, t) |
653 |
|
654 |
-- | Build an object declaration. |
655 |
buildObject :: String -> String -> [Field] -> Q [Dec] |
656 |
buildObject sname field_pfx fields = do |
657 |
let name = mkName sname |
658 |
fields_d <- mapM (fieldTypeInfo field_pfx) fields |
659 |
let decl_d = RecC name fields_d |
660 |
let declD = DataD [] name [] [decl_d] [''Show, ''Read, ''Eq] |
661 |
ser_decls <- buildObjectSerialisation sname fields |
662 |
return $ declD:ser_decls |
663 |
|
664 |
-- | Generates an object definition: data type and its JSON instance. |
665 |
buildObjectSerialisation :: String -> [Field] -> Q [Dec] |
666 |
buildObjectSerialisation sname fields = do |
667 |
let name = mkName sname |
668 |
savedecls <- genSaveObject saveObjectField sname fields |
669 |
(loadsig, loadfn) <- genLoadObject loadObjectField sname fields |
670 |
shjson <- objectShowJSON sname |
671 |
rdjson <- objectReadJSON sname |
672 |
let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) |
673 |
[rdjson, shjson] |
674 |
return $ savedecls ++ [loadsig, loadfn, instdecl] |
675 |
|
676 |
-- | The toDict function name for a given type. |
677 |
toDictName :: String -> Name |
678 |
toDictName sname = mkName ("toDict" ++ sname) |
679 |
|
680 |
-- | Generates the save object functionality. |
681 |
genSaveObject :: (Name -> Field -> Q Exp) |
682 |
-> String -> [Field] -> Q [Dec] |
683 |
genSaveObject save_fn sname fields = do |
684 |
let name = mkName sname |
685 |
fnames <- mapM (newName . fieldVariable) fields |
686 |
let pat = conP name (map varP fnames) |
687 |
let tdname = toDictName sname |
688 |
tdsigt <- [t| $(conT name) -> [(String, JSON.JSValue)] |] |
689 |
|
690 |
let felems = map (uncurry save_fn) (zip fnames fields) |
691 |
flist = listE felems |
692 |
-- and finally convert all this to a json object |
693 |
tdlist = [| concat $flist |] |
694 |
iname = mkName "i" |
695 |
tclause <- clause [pat] (normalB tdlist) [] |
696 |
cclause <- [| $(varNameE "makeObj") . $(varE tdname) |] |
697 |
let fname = mkName ("save" ++ sname) |
698 |
sigt <- [t| $(conT name) -> JSON.JSValue |] |
699 |
return [SigD tdname tdsigt, FunD tdname [tclause], |
700 |
SigD fname sigt, ValD (VarP fname) (NormalB cclause) []] |
701 |
|
702 |
-- | Generates the code for saving an object's field, handling the |
703 |
-- various types of fields that we have. |
704 |
saveObjectField :: Name -> Field -> Q Exp |
705 |
saveObjectField fvar field = |
706 |
case fieldIsOptional field of |
707 |
OptionalOmitNull -> [| case $(varE fvar) of |
708 |
Nothing -> [] |
709 |
Just v -> [( $nameE, JSON.showJSON v )] |
710 |
|] |
711 |
OptionalSerializeNull -> [| case $(varE fvar) of |
712 |
Nothing -> [( $nameE, JSON.JSNull )] |
713 |
Just v -> [( $nameE, JSON.showJSON v )] |
714 |
|] |
715 |
NotOptional -> |
716 |
case fieldShow field of |
717 |
Nothing -> [| [( $nameE, JSON.showJSON $fvarE)] |] |
718 |
Just fn -> [| let (actual, extra) = $fn $fvarE |
719 |
in extra ++ [( $nameE, JSON.showJSON actual)] |
720 |
|] |
721 |
where nameE = stringE (fieldName field) |
722 |
fvarE = varE fvar |
723 |
|
724 |
-- | Generates the showJSON clause for a given object name. |
725 |
objectShowJSON :: String -> Q Dec |
726 |
objectShowJSON name = do |
727 |
body <- [| JSON.showJSON . $(varE . mkName $ "save" ++ name) |] |
728 |
return $ FunD (mkName "showJSON") [Clause [] (NormalB body) []] |
729 |
|
730 |
-- | Generates the load object functionality. |
731 |
genLoadObject :: (Field -> Q (Name, Stmt)) |
732 |
-> String -> [Field] -> Q (Dec, Dec) |
733 |
genLoadObject load_fn sname fields = do |
734 |
let name = mkName sname |
735 |
funname = mkName $ "load" ++ sname |
736 |
arg1 = mkName "v" |
737 |
objname = mkName "o" |
738 |
opid = mkName "op_id" |
739 |
st1 <- bindS (varP objname) [| liftM JSON.fromJSObject |
740 |
(JSON.readJSON $(varE arg1)) |] |
741 |
fbinds <- mapM load_fn fields |
742 |
let (fnames, fstmts) = unzip fbinds |
743 |
let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames |
744 |
fstmts' = st1:fstmts ++ [NoBindS (AppE (VarE 'return) cval)] |
745 |
sigt <- [t| JSON.JSValue -> JSON.Result $(conT name) |] |
746 |
return $ (SigD funname sigt, |
747 |
FunD funname [Clause [VarP arg1] (NormalB (DoE fstmts')) []]) |
748 |
|
749 |
-- | Generates code for loading an object's field. |
750 |
loadObjectField :: Field -> Q (Name, Stmt) |
751 |
loadObjectField field = do |
752 |
let name = fieldVariable field |
753 |
fvar <- newName name |
754 |
-- these are used in all patterns below |
755 |
let objvar = varNameE "o" |
756 |
objfield = stringE (fieldName field) |
757 |
loadexp = |
758 |
if fieldIsOptional field /= NotOptional |
759 |
-- we treat both optional types the same, since |
760 |
-- 'maybeFromObj' can deal with both missing and null values |
761 |
-- appropriately (the same) |
762 |
then [| $(varNameE "maybeFromObj") $objvar $objfield |] |
763 |
else case fieldDefault field of |
764 |
Just defv -> |
765 |
[| $(varNameE "fromObjWithDefault") $objvar |
766 |
$objfield $defv |] |
767 |
Nothing -> [| $(varNameE "fromObj") $objvar $objfield |] |
768 |
bexp <- loadFn field loadexp objvar |
769 |
|
770 |
return (fvar, BindS (VarP fvar) bexp) |
771 |
|
772 |
-- | Builds the readJSON instance for a given object name. |
773 |
objectReadJSON :: String -> Q Dec |
774 |
objectReadJSON name = do |
775 |
let s = mkName "s" |
776 |
body <- [| case JSON.readJSON $(varE s) of |
777 |
JSON.Ok s' -> $(varE .mkName $ "load" ++ name) s' |
778 |
JSON.Error e -> |
779 |
JSON.Error $ "Can't parse value for type " ++ |
780 |
$(stringE name) ++ ": " ++ e |
781 |
|] |
782 |
return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []] |
783 |
|
784 |
-- * Inheritable parameter tables implementation |
785 |
|
786 |
-- | Compute parameter type names. |
787 |
paramTypeNames :: String -> (String, String) |
788 |
paramTypeNames root = ("Filled" ++ root ++ "Params", |
789 |
"Partial" ++ root ++ "Params") |
790 |
|
791 |
-- | Compute information about the type of a parameter field. |
792 |
paramFieldTypeInfo :: String -> Field -> Q (Name, Strict, Type) |
793 |
paramFieldTypeInfo field_pfx fd = do |
794 |
t <- actualFieldType fd |
795 |
let n = mkName . (++ "P") . (field_pfx ++) . |
796 |
fieldRecordName $ fd |
797 |
return (n, NotStrict, AppT (ConT ''Maybe) t) |
798 |
|
799 |
-- | Build a parameter declaration. |
800 |
-- |
801 |
-- This function builds two different data structures: a /filled/ one, |
802 |
-- in which all fields are required, and a /partial/ one, in which all |
803 |
-- fields are optional. Due to the current record syntax issues, the |
804 |
-- fields need to be named differrently for the two structures, so the |
805 |
-- partial ones get a /P/ suffix. |
806 |
buildParam :: String -> String -> [Field] -> Q [Dec] |
807 |
buildParam sname field_pfx fields = do |
808 |
let (sname_f, sname_p) = paramTypeNames sname |
809 |
name_f = mkName sname_f |
810 |
name_p = mkName sname_p |
811 |
fields_f <- mapM (fieldTypeInfo field_pfx) fields |
812 |
fields_p <- mapM (paramFieldTypeInfo field_pfx) fields |
813 |
let decl_f = RecC name_f fields_f |
814 |
decl_p = RecC name_p fields_p |
815 |
let declF = DataD [] name_f [] [decl_f] [''Show, ''Read, ''Eq] |
816 |
declP = DataD [] name_p [] [decl_p] [''Show, ''Read, ''Eq] |
817 |
ser_decls_f <- buildObjectSerialisation sname_f fields |
818 |
ser_decls_p <- buildPParamSerialisation sname_p fields |
819 |
fill_decls <- fillParam sname field_pfx fields |
820 |
return $ [declF, declP] ++ ser_decls_f ++ ser_decls_p ++ fill_decls ++ |
821 |
buildParamAllFields sname fields ++ |
822 |
buildDictObjectInst name_f sname_f |
823 |
|
824 |
-- | Builds a list of all fields of a parameter. |
825 |
buildParamAllFields :: String -> [Field] -> [Dec] |
826 |
buildParamAllFields sname fields = |
827 |
let vname = mkName ("all" ++ sname ++ "ParamFields") |
828 |
sig = SigD vname (AppT ListT (ConT ''String)) |
829 |
val = ListE $ map (LitE . StringL . fieldName) fields |
830 |
in [sig, ValD (VarP vname) (NormalB val) []] |
831 |
|
832 |
-- | Builds the 'DictObject' instance for a filled parameter. |
833 |
buildDictObjectInst :: Name -> String -> [Dec] |
834 |
buildDictObjectInst name sname = |
835 |
[InstanceD [] (AppT (ConT ''DictObject) (ConT name)) |
836 |
[ValD (VarP 'toDict) (NormalB (VarE (toDictName sname))) []]] |
837 |
|
838 |
-- | Generates the serialisation for a partial parameter. |
839 |
buildPParamSerialisation :: String -> [Field] -> Q [Dec] |
840 |
buildPParamSerialisation sname fields = do |
841 |
let name = mkName sname |
842 |
savedecls <- genSaveObject savePParamField sname fields |
843 |
(loadsig, loadfn) <- genLoadObject loadPParamField sname fields |
844 |
shjson <- objectShowJSON sname |
845 |
rdjson <- objectReadJSON sname |
846 |
let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) |
847 |
[rdjson, shjson] |
848 |
return $ savedecls ++ [loadsig, loadfn, instdecl] |
849 |
|
850 |
-- | Generates code to save an optional parameter field. |
851 |
savePParamField :: Name -> Field -> Q Exp |
852 |
savePParamField fvar field = do |
853 |
checkNonOptDef field |
854 |
let actualVal = mkName "v" |
855 |
normalexpr <- saveObjectField actualVal field |
856 |
-- we have to construct the block here manually, because we can't |
857 |
-- splice-in-splice |
858 |
return $ CaseE (VarE fvar) [ Match (ConP 'Nothing []) |
859 |
(NormalB (ConE '[])) [] |
860 |
, Match (ConP 'Just [VarP actualVal]) |
861 |
(NormalB normalexpr) [] |
862 |
] |
863 |
|
864 |
-- | Generates code to load an optional parameter field. |
865 |
loadPParamField :: Field -> Q (Name, Stmt) |
866 |
loadPParamField field = do |
867 |
checkNonOptDef field |
868 |
let name = fieldName field |
869 |
fvar <- newName name |
870 |
-- these are used in all patterns below |
871 |
let objvar = varNameE "o" |
872 |
objfield = stringE name |
873 |
loadexp = [| $(varNameE "maybeFromObj") $objvar $objfield |] |
874 |
bexp <- loadFn field loadexp objvar |
875 |
return (fvar, BindS (VarP fvar) bexp) |
876 |
|
877 |
-- | Builds a simple declaration of type @n_x = fromMaybe f_x p_x@. |
878 |
buildFromMaybe :: String -> Q Dec |
879 |
buildFromMaybe fname = |
880 |
valD (varP (mkName $ "n_" ++ fname)) |
881 |
(normalB [| $(varNameE "fromMaybe") |
882 |
$(varNameE $ "f_" ++ fname) |
883 |
$(varNameE $ "p_" ++ fname) |]) [] |
884 |
|
885 |
-- | Builds a function that executes the filling of partial parameter |
886 |
-- from a full copy (similar to Python's fillDict). |
887 |
fillParam :: String -> String -> [Field] -> Q [Dec] |
888 |
fillParam sname field_pfx fields = do |
889 |
let fnames = map (\fd -> field_pfx ++ fieldRecordName fd) fields |
890 |
(sname_f, sname_p) = paramTypeNames sname |
891 |
oname_f = "fobj" |
892 |
oname_p = "pobj" |
893 |
name_f = mkName sname_f |
894 |
name_p = mkName sname_p |
895 |
fun_name = mkName $ "fill" ++ sname ++ "Params" |
896 |
le_full = ValD (ConP name_f (map (VarP . mkName . ("f_" ++)) fnames)) |
897 |
(NormalB . VarE . mkName $ oname_f) [] |
898 |
le_part = ValD (ConP name_p (map (VarP . mkName . ("p_" ++)) fnames)) |
899 |
(NormalB . VarE . mkName $ oname_p) [] |
900 |
obj_new = foldl (\accu vname -> AppE accu (VarE vname)) (ConE name_f) |
901 |
$ map (mkName . ("n_" ++)) fnames |
902 |
le_new <- mapM buildFromMaybe fnames |
903 |
funt <- [t| $(conT name_f) -> $(conT name_p) -> $(conT name_f) |] |
904 |
let sig = SigD fun_name funt |
905 |
fclause = Clause [VarP (mkName oname_f), VarP (mkName oname_p)] |
906 |
(NormalB $ LetE (le_full:le_part:le_new) obj_new) [] |
907 |
fun = FunD fun_name [fclause] |
908 |
return [sig, fun] |
909 |
|
910 |
-- * Template code for exceptions |
911 |
|
912 |
-- | Exception simple error message field. |
913 |
excErrMsg :: (String, Q Type) |
914 |
excErrMsg = ("errMsg", [t| String |]) |
915 |
|
916 |
-- | Builds an exception type definition. |
917 |
genException :: String -- ^ Name of new type |
918 |
-> SimpleObject -- ^ Constructor name and parameters |
919 |
-> Q [Dec] |
920 |
genException name cons = do |
921 |
let tname = mkName name |
922 |
declD <- buildSimpleCons tname cons |
923 |
(savesig, savefn) <- genSaveSimpleObj tname ("save" ++ name) cons $ |
924 |
uncurry saveExcCons |
925 |
(loadsig, loadfn) <- genLoadExc tname ("load" ++ name) cons |
926 |
return [declD, loadsig, loadfn, savesig, savefn] |
927 |
|
928 |
-- | Generates the \"save\" clause for an entire exception constructor. |
929 |
-- |
930 |
-- This matches the exception with variables named the same as the |
931 |
-- constructor fields (just so that the spliced in code looks nicer), |
932 |
-- and calls showJSON on it. |
933 |
saveExcCons :: String -- ^ The constructor name |
934 |
-> [SimpleField] -- ^ The parameter definitions for this |
935 |
-- constructor |
936 |
-> Q Clause -- ^ Resulting clause |
937 |
saveExcCons sname fields = do |
938 |
let cname = mkName sname |
939 |
fnames <- mapM (newName . fst) fields |
940 |
let pat = conP cname (map varP fnames) |
941 |
felems = if null fnames |
942 |
then conE '() -- otherwise, empty list has no type |
943 |
else listE $ map (\f -> [| JSON.showJSON $(varE f) |]) fnames |
944 |
let tup = tupE [ litE (stringL sname), felems ] |
945 |
clause [pat] (normalB [| JSON.showJSON $tup |]) [] |
946 |
|
947 |
-- | Generates load code for a single constructor of an exception. |
948 |
-- |
949 |
-- Generates the code (if there's only one argument, we will use a |
950 |
-- list, not a tuple: |
951 |
-- |
952 |
-- @ |
953 |
-- do |
954 |
-- (x1, x2, ...) <- readJSON args |
955 |
-- return $ Cons x1 x2 ... |
956 |
-- @ |
957 |
loadExcConstructor :: Name -> String -> [SimpleField] -> Q Exp |
958 |
loadExcConstructor inname sname fields = do |
959 |
let name = mkName sname |
960 |
f_names <- mapM (newName . fst) fields |
961 |
let read_args = AppE (VarE 'JSON.readJSON) (VarE inname) |
962 |
let binds = case f_names of |
963 |
[x] -> BindS (ListP [VarP x]) |
964 |
_ -> BindS (TupP (map VarP f_names)) |
965 |
cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) f_names |
966 |
return $ DoE [binds read_args, NoBindS (AppE (VarE 'return) cval)] |
967 |
|
968 |
{-| Generates the loadException function. |
969 |
|
970 |
This generates a quite complicated function, along the lines of: |
971 |
|
972 |
@ |
973 |
loadFn (JSArray [JSString name, args]) = case name of |
974 |
"A1" -> do |
975 |
(x1, x2, ...) <- readJSON args |
976 |
return $ A1 x1 x2 ... |
977 |
"a2" -> ... |
978 |
s -> fail $ "Unknown exception" ++ s |
979 |
loadFn v = fail $ "Expected array but got " ++ show v |
980 |
@ |
981 |
-} |
982 |
genLoadExc :: Name -> String -> SimpleObject -> Q (Dec, Dec) |
983 |
genLoadExc tname sname opdefs = do |
984 |
let fname = mkName sname |
985 |
exc_name <- newName "name" |
986 |
exc_args <- newName "args" |
987 |
exc_else <- newName "s" |
988 |
arg_else <- newName "v" |
989 |
fails <- [| fail $ "Unknown exception '" ++ $(varE exc_else) ++ "'" |] |
990 |
-- default match for unknown exception name |
991 |
let defmatch = Match (VarP exc_else) (NormalB fails) [] |
992 |
-- the match results (per-constructor blocks) |
993 |
str_matches <- |
994 |
mapM (\(s, params) -> do |
995 |
body_exp <- loadExcConstructor exc_args s params |
996 |
return $ Match (LitP (StringL s)) (NormalB body_exp) []) |
997 |
opdefs |
998 |
-- the first function clause; we can't use [| |] due to TH |
999 |
-- limitations, so we have to build the AST by hand |
1000 |
let clause1 = Clause [ConP 'JSON.JSArray |
1001 |
[ListP [ConP 'JSON.JSString [VarP exc_name], |
1002 |
VarP exc_args]]] |
1003 |
(NormalB (CaseE (AppE (VarE 'JSON.fromJSString) |
1004 |
(VarE exc_name)) |
1005 |
(str_matches ++ [defmatch]))) [] |
1006 |
-- the fail expression for the second function clause |
1007 |
fail_type <- [| fail $ "Invalid exception: expected '(string, [args])' " ++ |
1008 |
" but got " ++ show (pp_value $(varE arg_else)) ++ "'" |
1009 |
|] |
1010 |
-- the second function clause |
1011 |
let clause2 = Clause [VarP arg_else] (NormalB fail_type) [] |
1012 |
sigt <- [t| JSON.JSValue -> JSON.Result $(conT tname) |] |
1013 |
return $ (SigD fname sigt, FunD fname [clause1, clause2]) |