pragma('js', ...) inside if clause fails without meaningful message

Open

#642 opened on Jun 20, 2019 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 32/100

Issue type: Bug
Clarity: Mostly clear
Activity status: Stale
Tech stack: javascript, python
Domain: compilers

Research direction

Reproduce the issue with the direct and function-wrapped pragma('js', ...) examples, then inspect the compiler path handling pragma inside an if clause. Compare its behavior with the related module-compilation issue #640; done means the direct form produces a meaningful diagnostic instead of the empty error output.

Written by the indexing model from the issue text.

Description

STATE: under consideration

Doing this:

if __pragma__('js', 'obj instanceof Object'):
    pass

Fails with no messsage:

Transcrypt (TM) Python to JavaScript Small Sane Subset Transpiler Version 3.7.16
Copyright (C) Geatec Engineering. License: Apache 2.0



Error while compiling (offending file last):
        File 'd', line 1, namely:

        Error while compiling (offending file last):
        File 'd', line 1, namely:


Aborted

Wrapping in brackets won't helping:

if (__pragma__('js', '(obj instanceof Object)')):
    pass

Howerver wrapping in function surprisingly works:

if test(__pragma__('js', 'obj instanceof Object')):
    pass

This is even more dreadul together with another bug, which silences the error inside module and just skips module compilation if this pragma code is inside module:
https://github.com/QQuick/Transcrypt/issues/640

Dominant language: Python
Stars: 2.9k
Forks: 218
PR merge metrics: No merged PRs in 30d

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__pragma__('js', ...) inside if clause fails without meaningful message