"Container is falsy" error with babel-plugin-istanbul and @babel/plugin-transform-block-scoping

[jedwards1211]

💻

• Would you like to work on a fix?

How are you using Babel?

@babel/cli

Input code

for (let f; ; ) {
  f = "0";
  () => (0 ? 1 : parseInt(f));
}

Configuration file name

.babelrc

Configuration

{
  "plugins": ["babel-plugin-istanbul", "@babel/plugin-transform-block-scoping"]
}

Current and expected behavior

expected to transpile successfully, but I get:

ReferenceError: /Users/andy/gh/babel-plugin-istanbul-issue/index.js: Container is falsy
    at NodePath._replaceWith (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/path/replacement.js:139:11)
    at NodePath.replaceWith (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/path/replacement.js:127:8)
    at wrapLoopBody (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/plugin-transform-block-scoping/lib/loop.js:162:43)
    at PluginPass.Loop (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/plugin-transform-block-scoping/lib/index.js:82:50)
    at newFn (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/visitors.js:160:14)
    at NodePath._call (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/path/context.js:46:20)
    at NodePath.call (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/path/context.js:36:17)
    at NodePath.visit (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/path/context.js:82:31)
    at TraversalContext.visitQueue (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/context.js:89:16)
    at TraversalContext.visitMultiple (/Users/andy/gh/babel-plugin-istanbul-issue/node_modules/@babel/traverse/lib/context.js:61:17) {
  code: 'BABEL_TRANSFORM_ERROR'
}

Environment

• @babel/plugin-transform-block-scoping@7.23.4
• @babel/cli@7.23.9
• @babel/preset-env@7.24.0
• babel-plugin-istanbul@6.1.1

Possible solution

No response

Additional context

I'm not sure if this is babel's fault or babel-plugin-istanbul's fault, but I'm linking istanbuljs/babel-plugin-istanbul#289 here in case the babel team has any ideas.

The parseInt(f) gets transformed into cov_1c743zp148().b[0][1]++, parseInt(f). But for some reason that expression is orphaned by the time @babel/plugin-transform-block-scoping tries to rename f to _f, causing an error to be thrown.

[babel-bot]

Hey @jedwards1211! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

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[liuxingbaoyu]

I think the fix will be better in istanbul. Fortunately, istanbul only has one visitor Program, so it only need to add path.scope.crawl(); to synchronize the new binding information to completely fix this problem.

[jedwards1211]

I see, thank you! I'll make a PR