Method slice

lib/lines.ts:506–547

(start?: Pos, end?: Pos)

  }

  slice(start?: Pos, end?: Pos) {
    if (!end) {
      if (!start) {
        // The client seems to want a copy of this Lines object, but
        // Lines objects are immutable, so it's perfectly adequate to
        // return the same object.
        return this;
      }

      // Slice to the end if no end position was provided.
      end = this.lastPos();
    }

    if (!start) {
      throw new Error("cannot slice with end but not start");
    }

    const sliced = this.infos.slice(start.line - 1, end.line);

    if (start.line === end.line) {
      sliced[0] = sliceInfo(sliced[0], start.column, end.column);
    } else {
      assert.ok(start.line < end.line);
      sliced[0] = sliceInfo(sliced[0], start.column);
      sliced.push(sliceInfo(sliced.pop(), 0, end.column));
    }

    const lines = new Lines(sliced);

    if (this.mappings.length > 0) {
      const newMappings = lines.mappings;
      assert.strictEqual(newMappings.length, 0);
      this.mappings.forEach(function (this: any, mapping: any) {
        const sliced = mapping.slice(this, start, end);
        if (sliced) {
          newMappings.push(sliced);
        }
      }, this);
    }

    return lines;
  }

  bootstrapSliceString(start: Pos, end: Pos, options?: Options) {
    return this.slice(start, end).toString(options);