Method parsePipe

packages/compiler/src/expression_parser/parser.ts:820–885

()

  }

  private parsePipe(): AST {
    const start = this.inputIndex;
    let result = this.parseExpression();
    if (this.consumeOptionalOperator('|')) {
      if (this.parseFlags & ParseFlags.Action) {
        this.error(`Cannot have a pipe in an action expression`);
      }

      do {
        const nameStart = this.inputIndex;
        let nameId = this.expectIdentifierOrKeyword();
        let nameSpan: AbsoluteSourceSpan;
        let fullSpanEnd: number | undefined = undefined;
        if (nameId !== null) {
          nameSpan = this.sourceSpan(nameStart);
        } else {
          // No valid identifier was found, so we'll assume an empty pipe name ('').
          nameId = '';

          // However, there may have been whitespace present between the pipe character and the next
          // token in the sequence (or the end of input). We want to track this whitespace so that
          // the `BindingPipe` we produce covers not just the pipe character, but any trailing
          // whitespace beyond it. Another way of thinking about this is that the zero-length name
          // is assumed to be at the end of any whitespace beyond the pipe character.
          //
          // Therefore, we push the end of the `ParseSpan` for this pipe all the way up to the
          // beginning of the next token, or until the end of input if the next token is EOF.
          fullSpanEnd = this.next.index !== -1 ? this.next.index : this.input.length + this.offset;

          // The `nameSpan` for an empty pipe name is zero-length at the end of any whitespace
          // beyond the pipe character.
          nameSpan = new ParseSpan(fullSpanEnd, fullSpanEnd).toAbsolute(this.absoluteOffset);
        }

        const args: AST[] = [];
        while (this.consumeOptionalCharacter(chars.$COLON)) {
          args.push(this.parseExpression());

          // If there are additional expressions beyond the name, then the artificial end for the
          // name is no longer relevant.
        }
        let type: BindingPipeType;
        if (this.supportsDirectPipeReferences) {
          const charCode = nameId.charCodeAt(0);
          type =
            charCode === chars.$_ || (charCode >= chars.$A && charCode <= chars.$Z)
              ? BindingPipeType.ReferencedDirectly
              : BindingPipeType.ReferencedByName;
        } else {
          type = BindingPipeType.ReferencedByName;
        }

        result = new BindingPipe(
          this.span(start),
          this.sourceSpan(start, fullSpanEnd),
          result,
          nameId,
          args,