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bug(Printer): LF newline in template strings is escaped when it shouldn't be #59150

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maxpatiiuk opened this issue Jul 5, 2024 · 0 comments · Fixed by #60303
Closed

bug(Printer): LF newline in template strings is escaped when it shouldn't be #59150

maxpatiiuk opened this issue Jul 5, 2024 · 0 comments · Fixed by #60303
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@rbuckton
Labels
Bug A bug in TypeScript Domain: Transforms Relates to the public transform API Fix Available A PR has been opened for this issue
Milestone
TypeScript 5.7.1

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@maxpatiiuk
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maxpatiiuk commented Jul 5, 2024 •
edited
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🔎 Search Terms

template strings new line newline escape LF backslash emit print

🕗 Version & Regression Information

⏯ Playground Link

https://github.com/maxpatiiuk/typescript-bug-needless-lf-escaping/tree/main

💻 Code

import ts from 'typescript';

const expression = ts.factory.createNoSubstitutionTemplateLiteral('\n');

const printer = ts.createPrinter();
// LF new line gets escaped by the printer:
const printed = printer.printNode(
  ts.EmitHint.Unspecified,
  expression,
  ts.createSourceFile('index.ts', '', ts.ScriptTarget.Latest)
);

// Expected \n
// Received \\n
console.log(printed);
if (printed === '`\n`') console.log('Correct');
else if (printed === '`\\n`') console.error('Incorrect');

🙁 Actual behavior

LF new lines in template literal strings are escaped

🙂 Expected behavior

As the comment in TypeScript's source code states, LF new lines in backticks should not be escaped:

// Template strings preserve simple LF newlines, still encode CRLF (or CR)
const backtickQuoteEscapedCharsRegExp = /\r\n|[\\`\u0000-\u001f\t\v\f\b\r\u2028\u2029\u0085]/g;

https://github.com/microsoft/TypeScript/blame/3163fe7e3898c1f48cd9bc097b96e3426cd2a453/src/compiler/utilities.ts#L5925-L5926

However, that RegExp has a bug - the regex has a \u0000-\u001f character range, which includes the LF character (\u000a)

/[\u0000-\u001f]/.test('\n')
// -> true

The RegExp should be modified to not match \u000a (\n). Potentially like so:

- const backtickQuoteEscapedCharsRegExp = /\r\n|[\\`\u0000-\u001f\t\v\f\b\r\u2028\u2029\u0085]/g;
  const backtickQuoteEscapedCharsRegExp = /\r\n|[\\`\u0000-\u0009\u000b-\u001f\t\v\f\b\r\u2028\u2029\u0085]/g;

Additional information about the issue

No response
@andrewbranch andrewbranch added the Needs Investigation This issue needs a team member to investigate its status. label Jul 5, 2024
@andrewbranch andrewbranch added this to the TypeScript 5.6.0 milestone Jul 5, 2024
@rbuckton rbuckton mentioned this issue Oct 21, 2024
Merged
@typescript-bot typescript-bot added Fix Available A PR has been opened for this issue labels Oct 21, 2024
@rbuckton rbuckton added Bug A bug in TypeScript Domain: Transforms Relates to the public transform API and removed Needs Investigation This issue needs a team member to investigate its status. labels Oct 21, 2024
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Assignees

@rbuckton rbuckton

Labels
Bug A bug in TypeScript Domain: Transforms Relates to the public transform API Fix Available A PR has been opened for this issue
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Milestone
TypeScript 5.7.1
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Successfully merging a pull request may close this issue.

Fix template string escaping microsoft/TypeScript
5 participants
@DanielRosenwasser @andrewbranch @rbuckton @typescript-bot @maxpatiiuk