Synnefo » snf-ganeti

Use sum types instead of exceptions

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Exceptions make it hard to write functional code, as alternative

control flows need to be considered and compiler support is limited.

Therefore, Ganeti functions should never allow exceptions to escape.

Function that can fail should report failure by returning an appropriate

sum type (``Either`` or one of its glorified variants like ``Maybe`` or

``Result``); the preferred sum type for reporting errors is ``Result``.

As other Ganeti functions also follow these guide lines, they can safely

be composed. However, be careful when using functions from other libraries;

if they can raise exceptions, catch them, preferably as close to their

origin as reasonably possible.