Remove IIFE wrappers from dev invariant checks #16963
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The error transform works by replacing calls to `invariant` with an `if` statement. Since we're replacing a call expression with a statement, Babel wraps the new statement in an immediately-invoked function expression (IIFE). This wrapper is unnecessary in practice because our `invariant` calls are always part of their own expression statement. In the production bundle, the function wrappers are removed by Closure. But they remain in the development bundles. This commit updates the transform to confirm that an `invariant` call expression's parent node is an expression statement. (If not, it throws a transform error.) Then, it replaces the expression statement instead of the expression itself, effectively removing the extraneous IIFE wrapper.
Details of bundled changes.Comparing: d3622d0...8307966 react-dom
react-art
react-native-renderer
react-test-renderer
react-reconciler
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bvaughn
approved these changes
Sep 30, 2019
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The error transform works by replacing calls to
invariantwith anifstatement.Since we're replacing a call expression with a statement, Babel wraps the new statement in an immediately-invoked function expression (IIFE). This wrapper is unnecessary in practice because our
invariantcalls are always part of their own expression statement.In the production bundle, the function wrappers are removed by Closure. But they remain in the development bundles.
This commit updates the transform to confirm that an
invariantcall expression's parent node is an expression statement. (If not, it throws a transform error.)Then, it replaces the expression statement instead of the expression itself, effectively removing the extraneous IIFE wrapper.