refactor(transformer): don't need to transform JSXExpression::EmptyExpression in JSX attributes

[Dunqing]

No description provided.

[Dunqing]

• refactor(transformer): don't need to transform JSXExpression::EmptyExpression in JSX attributes #8817 👈 (View in Graphite)
• docs(ast): correct documentation for JSXExpression::EmptyExpression  #8816
• feat(semantic): report error for empty JSX attribute expression #8815
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #8817 will not alter performance

_{Comparing 01-31-refactor_transformer_don_t_need_to_transform_jsxexpression_emptyexpression_in_jsx_attributes (1c1add7) with main (b00b8c8)}

Summary

✅ 33 untouched benchmarks

[Boshen]

We should not make this unreachable in situations where the semantic checker is not run or missed the check, do not emit anything instead.

[Dunqing]

That makes sense. To achieve "do not emit anything" here we must return a None, which will cause more changes, I will do this later.

[overlookmotel]

From reading the JSX spec, it doesn't look like an EmptyExpression is ever valid in this position. If I've understood that right, could we make JSXExpressionContainer just contain an Expression, rather than a JSXExpression?

I assume the reason is recoverability. To achieve that, could we instead raise an error in the parser, and skip adding the JSXAttribute, so that parsing can continue?

It's going to cause a problem serializing to ESTree, because what does it serialize to? The "EmptyExpression" option doesn't exist.

[Dunqing]

This is part of typescript-eslint, See https://ast.sxzz.dev/#eNpNzMEKwjAMgOFXGTlPvI+5o08gnnoJNUhH15SmFaX03Y1WZLfk+0kqeJhgxQeKTS5mGCEq5FekDgcS78LHrfp8Zh7wVNtiwlCbCfNRZdHKWqviYEC4JEsXfWFg0n3jW/E6jz2T3fBKSRyH3j1mkvzvCcP9e5lToZ+t8txJg/YGroc72A==.

I agree to throw an error in the parser as this is a pointless AST node.

[Boshen]

Re changing AST:

I double checked, it's a difficult change because we want the span in JSXExpressionContainer, and also support <div>{}</div>.

Close as not planned.