[Python] Cannot write a pattern to find useless list comprehensions #4260
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feature:matching
lang:python
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IagoAbal
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IagoAbal
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I had some refactoring I wanted to do to remove Metavariable.Id and just keep Metavariable.Name. This might solve this issue. |
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Hmm it's also because Naming_AST does not handle correctly those variables. The PatId has a resolved of Global 1 |
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(found via -dump_named_ast) |
aryx
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Dec 8, 2021
This closes #4260 test plan: test files included and also see how the same variables "v" now resolve to the same Local each time ``` $ semgrep-core -lang py -dump_named_ast python/metavar_iterator.py Pr( [DefStmt( ({ name=EN( Id(("test", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref( None); id_constness=Ref(None); })); attrs=[]; tparams=[]; }, FuncDef( {fkind=(Function, ()); fparams=[]; frettype=None; fbody=FBStmt( Block( [ExprStmt( Comprehension(List, (N( Id(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 1))); id_type=Ref(None); id_constness=Ref(None); })), [CompFor((), PatId(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 1))); id_type=Ref(None); id_constness=Ref(None); }), (), N( Id(("iterator", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref(None); id_constness=Ref( None); })))])), ()); ExprStmt( Comprehension(List, (Call( N( Id(("f", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref(None); id_constness=Ref(None); })), [Arg( N( Id(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 2))); id_type=Ref(None); id_constness=Ref( None); })))]), [CompFor((), PatId(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 2))); id_type=Ref(None); id_constness=Ref(None); }), (), N( Id(("iterator", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref(None); id_constness=Ref( None); })))])), ())])); })))]) ```
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aryx
added a commit
that referenced
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Dec 8, 2021
This closes #4260 test plan: test files included and also see how the same variables "v" now resolve to the same Local each time ``` $ semgrep-core -lang py -dump_named_ast python/metavar_iterator.py Pr( [DefStmt( ({ name=EN( Id(("test", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref( None); id_constness=Ref(None); })); attrs=[]; tparams=[]; }, FuncDef( {fkind=(Function, ()); fparams=[]; frettype=None; fbody=FBStmt( Block( [ExprStmt( Comprehension(List, (N( Id(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 1))); id_type=Ref(None); id_constness=Ref(None); })), [CompFor((), PatId(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 1))); id_type=Ref(None); id_constness=Ref(None); }), (), N( Id(("iterator", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref(None); id_constness=Ref( None); })))])), ()); ExprStmt( Comprehension(List, (Call( N( Id(("f", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref(None); id_constness=Ref(None); })), [Arg( N( Id(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 2))); id_type=Ref(None); id_constness=Ref( None); })))]), [CompFor((), PatId(("v", ()), {id_hidden=false; id_resolved=Ref(Some((Local, 2))); id_type=Ref(None); id_constness=Ref(None); }), (), N( Id(("iterator", ()), {id_hidden=false; id_resolved=Ref(None); id_type=Ref(None); id_constness=Ref( None); })))])), ())])); })))]) ```
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Reporting on behalf of @mhoffm-aiven.
Describe the bug
Pattern
[$X for $X in $ITERATOR]does not match[v for v in iterator]. The cause seems to be that in Generic, the firstvis an expression id, whereas the secondvis a pattern id. We should probably consider both equal when they bind to the same metavariable.To Reproduce
https://semgrep.dev/s/Q91Z
Expected behavior
Pattern works, or we provide some workaround.
What is the priority of the bug to you?
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