Printer breaks when there is \ in string literal in jsx attrs

[kgtkr]

TypeScript Version: typescript@3.8.0-dev.20191105

Search Terms:
compilar api

Code

fs.writeFileSync(
  "out",
  ts
    .createPrinter()
    .printFile(
      ts.createSourceFile(
        "test.ts",
        fs.readFileSync("in", { encoding: "utf8" }),
        ts.ScriptTarget.ESNext,
        undefined,
        ts.ScriptKind.TSX
      )
    )
)

in

<a x="\\"/>

Expected behavior:

out

<a x="\\"/>

Actual behavior:
out

<a x="\\\\"/>

Playground Link:

Related Issues:

[RyanCavanaugh]

Confirmed repro. Running tsc normally on this input generates the correct output.

[rbuckton]

Would this be considered a bug? The issue is due to the fact the string literal node for "\\" doesn't have a parent pointer (because the setParentNodes argument of createSourceFile was passed undefined), so we can't determine the source file the node belongs to. We use the source file to extract the actual literal text, and when we can't find the source file we fall back to emitting the literal as best we can (with no knowledge of the surrounding code). This means we escape the "\\" as "\\\\" since we can only assume this is a JavaScript string literal, not a JSX attribute string.

[rbuckton]

I'm looking into solving this by adding EmitHint.Jsx, which can be used to ensure the correct encoding for string literals in Jsx Attributes.