apple/pkl · error · ParserError

invalidLineContinuationEscapeSequenceWhitespace

invalidLineContinuationEscapeSequenceWhitespace

Error message

Invalid line continuation escape sequence.

Whitespace between the continuation escape and following newline is not allowed.

What it means

Pkl treats `\` followed by a newline as a line continuation inside strings, but the escape sequence `\` was followed by whitespace (spaces/tabs) before the newline, which is not allowed. The lexer detects `\` + [ \t]+ + newline and reports that the whitespace between the continuation escape and the newline is invalid.

Source

Thrown at pkl-parser/src/main/java/org/pkl/parser/Lexer.java:475

        var scope = interpolationStack.getFirst();
        scope.parens++;
        state = State.DEFAULT;
        yield Token.INTERPOLATION_START;
      }
      case 'u' -> lexUnicodeEscape();
      case '\n' -> Token.STRING_ESCAPE_CONTINUATION;
      case '\r' -> {
        if (lookahead == '\n') {
          nextChar();
        }
        yield Token.STRING_ESCAPE_CONTINUATION;
      }
      case ' ', '\t' -> {
        var c = cursor;
        var next = nextChar();
        while (next == ' ' || next == '\t') next = nextChar();
        if (next == '\n' || next == '\r')
          throw lexError(
              ErrorMessages.create("invalidLineContinuationEscapeSequenceWhitespace"),
              c - 2,
              cursor - c + 2);

        throw lexError(
            ErrorMessages.create("invalidCharacterEscapeSequence", "\\" + (char) ch, "\\"),
            c - 2,
            2);
      }
      default ->
          throw lexError(
              ErrorMessages.create("invalidCharacterEscapeSequence", "\\" + (char) ch, "\\"),
              cursor - 2,
              2);
    };
  }

  private Token lexUnicodeEscape() {

View on GitHub (pinned to f3efcbfc9b)

Solutions

1. Remove all spaces/tabs between the `\` and the newline so `\` is immediately followed by the line break.
2. If the whitespace is meaningful, move it after the newline or into the string content of the next line.
3. If no continuation was intended, escape the backslash as `\\` so the trailing spaces become ordinary characters.

Example fix

// before
long = "first line \   
second"
// after
long = "first line \
second"

function badContinuation(src) { return /\\[ \t]+(\r?\n)/.test(src); }
if (badContinuation(src)) throw new Error('Whitespace after line-continuation backslash is not allowed');

null

try { tokens = lexer.next(); } catch (e) { if (e.code === 'invalidLineContinuationEscapeSequenceWhitespace') { console.error('Remove spaces/tabs after \\ before newline'); } throw e; }

When it happens

Trigger: nextString → lexEscape, case ' ' or '\t': after a backslash, the next characters are one or more spaces/tabs and then a `\n` or `\r`. E.g. `"foo \ "` where a space slipped in between `\` and the line break.

Common situations: Editors auto-trimming... or rather auto-indenting the next line leaving trailing spaces before the newline; hand-formatting a long string and accidentally typing spaces after the `\`; copy-paste where a line continuation `\` gained trailing whitespace; lint formatters inserting alignment spaces after the backslash.

Related errors

• invalidCharacterEscapeSequence
• unexpectedCharacter
• unterminatedUnicodeEscapeSequence
• invalidUnicodeEscapeSequence
• unseparatedObjectMembers

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/fe92390545f076c4. Report an issue: GitHub.