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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,89 @@ | ||
| // Based on https://repl.it/site/blog/infinite-loops by Amjad Masad. | ||
|
|
||
| export default function TransformDetectInfiniteLoop({ types: t }) { | ||
| const MAX_ITERATIONS = 2000; | ||
| const MAX_LOOP_TIME_MS = 1500; | ||
|
|
||
| return { | ||
| visitor: { | ||
| 'WhileStatement|ForStatement|DoWhileStatement': (path: any) => { | ||
| const startTime = t.identifier('startTime'); | ||
| path.scope.parent.push({ | ||
| id: startTime, | ||
| init: t.numericLiteral(0) | ||
| }); | ||
|
|
||
| // An iterator that is incremented with each iteration | ||
| const iterator = t.identifier('loopIt'); | ||
| path.scope.parent.push({ | ||
| id: iterator, | ||
| init: t.numericLiteral(0) | ||
| }); | ||
|
|
||
| // re-initialize counter variable | ||
| const countReInitializer = t.assignmentExpression('=', t.identifier(iterator.name), t.numericLiteral(0)); | ||
| // re-initialize counter variable for this loop | ||
| path.insertBefore(t.expressionStatement(countReInitializer)); | ||
|
|
||
| // re-initialize time variable | ||
| // will begin counting execution time from before the loop starts | ||
| const timeReInitializer = t.assignmentExpression('=', t.identifier('startTime'), t.callExpression( | ||
| t.identifier('performance.now'), | ||
| [] | ||
| )); | ||
| path.insertBefore(t.expressionStatement(timeReInitializer)); | ||
|
|
||
|
|
||
| /* | ||
| * throw RangeError if loop | ||
| * 1. does over MAX_ITERATIONS iterations | ||
| * 2. takes more than MAX_LOOP_TIME_MS to complete | ||
| */ | ||
| const guard = t.ifStatement( | ||
| t.logicalExpression( | ||
| '&&', | ||
| t.binaryExpression( | ||
| '>', | ||
| t.updateExpression( | ||
| '++', | ||
| iterator, | ||
| true, | ||
| ), | ||
| t.numericLiteral(MAX_ITERATIONS), | ||
| ), | ||
| t.binaryExpression( | ||
| '>', | ||
| t.binaryExpression( | ||
| '-', | ||
| t.callExpression(t.identifier('performance.now'), []), | ||
| startTime | ||
| ), | ||
| t.numericLiteral(MAX_LOOP_TIME_MS) | ||
| ), | ||
| ), | ||
| t.throwStatement( | ||
| t.newExpression( | ||
| t.identifier('RangeError'), | ||
| [t.stringLiteral( | ||
| 'Potential infinite loop', | ||
| )], | ||
| ), | ||
| ), | ||
| ); | ||
|
|
||
| // No block statment e.g. `while (1) 1;` | ||
| if (!path.get('body').isBlockStatement()) { | ||
| const statement = path.get('body').node; | ||
| path.get('body').replaceWith( | ||
| t.blockStatement([ | ||
| guard, | ||
| statement, | ||
| ]), | ||
| ); | ||
| } else { | ||
| path.get('body').unshiftContainer('body', guard); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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