Don't raise exception in evaluate() if parsing expr returns None
#1547
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mmatera
reviewed
Dec 19, 2025
mathics/session.py
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| if form is None: | ||
| form = self.form | ||
| self.last_result = expr.evaluate(self.evaluation) | ||
| self.last_result = expr.evaluate(self.evaluation) if expr else None |
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In WMA, an empty expression should result in Null (SymbolNull). I think that what we should do here instead is to check in line 147 if expr is None, and return SymbolNull.
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Thanks. I've updated the PR accordingly.
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Thanks. I've updated the PR accordingly.
Thanks. LGTM. (And thanks @mmatera for spotting.)
rocky
changed the title
evaluate() if parsing expr returns None
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This can happen for example if you give it a string consisting of just a comment. I'm not sure if this behavior - returning None - is correct, but at least it's consistent with what parse does.
Also I suppose there should be a test for this, but not sure where the best place for it would be.