angular-docs-cn/packages/compiler-cli/ngcc/test/sourcemaps/source_file_spec.ts

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import {encode} from 'sourcemap-codec';

import {absoluteFrom} from '../../../src/ngtsc/file_system';
import {runInEachFileSystem} from '../../../src/ngtsc/file_system/testing';
import {RawSourceMap} from '../../src/sourcemaps/raw_source_map';
import {SegmentMarker} from '../../src/sourcemaps/segment_marker';
import {computeStartOfLinePositions, ensureOriginalSegmentLinks, extractOriginalSegments, findLastMappingIndexBefore, Mapping, parseMappings, SourceFile} from '../../src/sourcemaps/source_file';

runInEachFileSystem(() => {
  describe('SourceFile and utilities', () => {
    let _: typeof absoluteFrom;

    beforeEach(() => {
      _ = absoluteFrom;
    });

    describe('parseMappings()', () => {
      it('should be an empty array for source files with no source map', () => {
        const mappings = parseMappings(null, [], []);
        expect(mappings).toEqual([]);
      });

      it('should be empty array for source files with no source map mappings', () => {
        const rawSourceMap: RawSourceMap = {mappings: '', names: [], sources: [], version: 3};
        const mappings = parseMappings(rawSourceMap, [], []);
        expect(mappings).toEqual([]);
      });

      it('should parse the mappings from the raw source map', () => {
        const rawSourceMap: RawSourceMap = {
          mappings: encode([[[0, 0, 0, 0], [6, 0, 0, 3]]]),
          names: [],
          sources: ['a.js'],
          version: 3
        };
        const originalSource = new SourceFile(_('/foo/src/a.js'), 'abcdefg', null, false, []);
        const mappings = parseMappings(rawSourceMap, [originalSource], [0, 8]);
        expect(mappings).toEqual([
          {
            generatedSegment: {line: 0, column: 0, position: 0, next: undefined},
            originalSource,
            originalSegment: {line: 0, column: 0, position: 0, next: undefined},
            name: undefined
          },
          {
            generatedSegment: {line: 0, column: 6, position: 6, next: undefined},
            originalSource,
            originalSegment: {line: 0, column: 3, position: 3, next: undefined},
            name: undefined
          },
        ]);
      });
    });

    describe('extractOriginalSegments()', () => {
      it('should return an empty Map for source files with no source map', () => {
        expect(extractOriginalSegments(parseMappings(null, [], []))).toEqual(new Map());
      });

      it('should be empty Map for source files with no source map mappings', () => {
        const rawSourceMap: RawSourceMap = {mappings: '', names: [], sources: [], version: 3};
        expect(extractOriginalSegments(parseMappings(rawSourceMap, [], []))).toEqual(new Map());
      });

      it('should parse the segments in ascending order of original position from the raw source map',
         () => {
           const originalSource = new SourceFile(_('/foo/src/a.js'), 'abcdefg', null, false, []);
           const rawSourceMap: RawSourceMap = {
             mappings: encode([[[0, 0, 0, 0], [2, 0, 0, 3], [4, 0, 0, 2]]]),
             names: [],
             sources: ['a.js'],
             version: 3
           };
           const originalSegments =
               extractOriginalSegments(parseMappings(rawSourceMap, [originalSource], [0, 8]));
           expect(originalSegments.get(originalSource)).toEqual([
             {line: 0, column: 0, position: 0, next: undefined},
             {line: 0, column: 2, position: 2, next: undefined},
             {line: 0, column: 3, position: 3, next: undefined},
           ]);
         });

      it('should create separate arrays for each original source file', () => {
        const sourceA = new SourceFile(_('/foo/src/a.js'), 'abcdefg', null, false, []);
        const sourceB = new SourceFile(_('/foo/src/b.js'), '1234567', null, false, []);
        const rawSourceMap: RawSourceMap = {
          mappings:
              encode([[[0, 0, 0, 0], [2, 1, 0, 3], [4, 0, 0, 2], [5, 1, 0, 5], [6, 1, 0, 2]]]),
          names: [],
          sources: ['a.js', 'b.js'],
          version: 3
        };
        const originalSegments =
            extractOriginalSegments(parseMappings(rawSourceMap, [sourceA, sourceB], [0, 8]));
        expect(originalSegments.get(sourceA)).toEqual([
          {line: 0, column: 0, position: 0, next: undefined},
          {line: 0, column: 2, position: 2, next: undefined},
        ]);
        expect(originalSegments.get(sourceB)).toEqual([
          {line: 0, column: 2, position: 2, next: undefined},
          {line: 0, column: 3, position: 3, next: undefined},
          {line: 0, column: 5, position: 5, next: undefined},
        ]);
      });
    });

    describe('findLastMappingIndexBefore', () => {
      it('should find the highest mapping index that has a segment marker below the given one if there is not an exact match',
         () => {
           const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
           const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
           const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
           const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
           const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
           const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
               marker => ({generatedSegment: marker} as Mapping));

           const marker: SegmentMarker = {line: 0, column: 35, position: 35, next: undefined};
           const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 0);
           expect(index).toEqual(2);
         });

      it('should find the highest mapping index that has a segment marker (when there are duplicates) below the given one if there is not an exact match',
         () => {
           const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
           const marker4: SegmentMarker = {line: 0, column: 30, position: 30, next: marker5};
           const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
           const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
           const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
           const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
               marker => ({generatedSegment: marker} as Mapping));

           const marker: SegmentMarker = {line: 0, column: 35, position: 35, next: undefined};
           const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 0);
           expect(index).toEqual(3);
         });

      it('should find the last mapping if the segment marker is higher than all of them', () => {
        const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
        const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
        const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
        const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
        const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
        const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
            marker => ({generatedSegment: marker} as Mapping));

        const marker: SegmentMarker = {line: 0, column: 60, position: 60, next: undefined};

        const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 0);
        expect(index).toEqual(4);
      });

      it('should return -1 if the segment marker is lower than all of them', () => {
        const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
        const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
        const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
        const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
        const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
        const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
            marker => ({generatedSegment: marker} as Mapping));

        const marker: SegmentMarker = {line: 0, column: 5, position: 5, next: undefined};

        const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 0);
        expect(index).toEqual(-1);
      });

      describe('[exact match inclusive]', () => {
        it('should find the matching segment marker mapping index if there is only one of them',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};

             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));
             const index = findLastMappingIndexBefore(mappings, marker3, /* exclusive */ false, 0);
             expect(index).toEqual(2);
           });

        it('should find the highest matching segment marker mapping index if there is more than one of them',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 30, position: 30, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};

             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));
             const index = findLastMappingIndexBefore(mappings, marker3, /* exclusive */ false, 0);
             expect(index).toEqual(3);
           });
      });

      describe('[exact match exclusive]', () => {
        it('should find the preceding mapping index if there is a matching segment marker', () => {
          const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
          const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
          const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
          const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
          const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};

          const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
              marker => ({generatedSegment: marker} as Mapping));
          const index = findLastMappingIndexBefore(mappings, marker3, /* exclusive */ true, 0);
          expect(index).toEqual(1);
        });

        it('should find the highest preceding mapping index if there is more than one matching segment marker',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 30, position: 30, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};

             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));
             const index = findLastMappingIndexBefore(mappings, marker3, /* exclusive */ false, 0);
             expect(index).toEqual(3);
           });
      });

      describe('[with lowerIndex hint', () => {
        it('should find the highest mapping index above the lowerIndex hint that has a segment marker below the given one if there is not an exact match',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));

             const marker: SegmentMarker = {line: 0, column: 35, position: 35, next: undefined};
             const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 1);
             expect(index).toEqual(2);
           });

        it('should return the lowerIndex mapping index if there is a single exact match and we are not exclusive',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));

             const marker: SegmentMarker = {line: 0, column: 30, position: 30, next: undefined};
             const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 2);
             expect(index).toEqual(2);
           });

        it('should return the lowerIndex mapping index if there are multiple exact matches and we are not exclusive',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 30, position: 30, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));

             const marker: SegmentMarker = {line: 0, column: 30, position: 30, next: undefined};
             const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 3);
             expect(index).toEqual(3);
           });

        it('should return -1 if the segment marker is lower than the lowerIndex hint', () => {
          const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
          const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
          const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
          const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
          const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
          const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
              marker => ({generatedSegment: marker} as Mapping));

          const marker: SegmentMarker = {line: 0, column: 25, position: 25, next: undefined};

          const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ false, 2);
          expect(index).toEqual(-1);
        });

        it('should return -1 if the segment marker is equal to the lowerIndex hint and we are exclusive',
           () => {
             const marker5: SegmentMarker = {line: 0, column: 50, position: 50, next: undefined};
             const marker4: SegmentMarker = {line: 0, column: 40, position: 40, next: marker5};
             const marker3: SegmentMarker = {line: 0, column: 30, position: 30, next: marker4};
             const marker2: SegmentMarker = {line: 0, column: 20, position: 20, next: marker3};
             const marker1: SegmentMarker = {line: 0, column: 10, position: 10, next: marker2};
             const mappings: Mapping[] = [marker1, marker2, marker3, marker4, marker5].map(
                 marker => ({generatedSegment: marker} as Mapping));

             const marker: SegmentMarker = {line: 0, column: 30, position: 30, next: undefined};

             const index = findLastMappingIndexBefore(mappings, marker, /* exclusive */ true, 2);
             expect(index).toEqual(-1);
           });
      });
    });

    describe('ensureOriginalSegmentLinks', () => {
      it('should add `next` properties to each segment that point to the next segment in the same source file',
         () => {
           const sourceA = new SourceFile(_('/foo/src/a.js'), 'abcdefg', null, false, []);
           const sourceB = new SourceFile(_('/foo/src/b.js'), '1234567', null, false, []);
           const rawSourceMap: RawSourceMap = {
             mappings:
                 encode([[[0, 0, 0, 0], [2, 1, 0, 3], [4, 0, 0, 2], [5, 1, 0, 5], [6, 1, 0, 2]]]),
             names: [],
             sources: ['a.js', 'b.js'],
             version: 3
           };
           const mappings = parseMappings(rawSourceMap, [sourceA, sourceB], [0, 8]);
           ensureOriginalSegmentLinks(mappings);
           expect(mappings[0].originalSegment.next).toBe(mappings[2].originalSegment);
           expect(mappings[1].originalSegment.next).toBe(mappings[3].originalSegment);
           expect(mappings[2].originalSegment.next).toBeUndefined();
           expect(mappings[3].originalSegment.next).toBeUndefined();
           expect(mappings[4].originalSegment.next).toBe(mappings[1].originalSegment);
         });
    });

    describe('SourceFile', () => {
      describe('flattenedMappings', () => {
        it('should be an empty array for source files with no source map', () => {
          const sourceFile =
              new SourceFile(_('/foo/src/index.js'), 'index contents', null, false, []);
          expect(sourceFile.flattenedMappings).toEqual([]);
        });

        it('should be empty array for source files with no source map mappings', () => {
          const rawSourceMap: RawSourceMap = {mappings: '', names: [], sources: [], version: 3};
          const sourceFile =
              new SourceFile(_('/foo/src/index.js'), 'index contents', rawSourceMap, false, []);
          expect(sourceFile.flattenedMappings).toEqual([]);
        });

        it('should be the same as non-flat mappings if there is only one level of source map',
           () => {
             const rawSourceMap: RawSourceMap = {
               mappings: encode([[[0, 0, 0, 0], [6, 0, 0, 3]]]),
               names: [],
               sources: ['a.js'],
               version: 3
             };
             const originalSource = new SourceFile(_('/foo/src/a.js'), 'abcdefg', null, false, []);
             const sourceFile = new SourceFile(
                 _('/foo/src/index.js'), 'abc123defg', rawSourceMap, false, [originalSource]);
             expect(removeOriginalSegmentLinks(sourceFile.flattenedMappings))
                 .toEqual(parseMappings(rawSourceMap, [originalSource], [0, 11]));
           });

        it('should merge mappings from flattened original source files', () => {
          const cSource = new SourceFile(_('/foo/src/c.js'), 'bcd123', null, false, []);
          const dSource = new SourceFile(_('/foo/src/d.js'), 'aef', null, false, []);

          const bSourceMap: RawSourceMap = {
            mappings: encode([[[0, 1, 0, 0], [1, 0, 0, 0], [4, 1, 0, 1]]]),
            names: [],
            sources: ['c.js', 'd.js'],
            version: 3
          };
          const bSource =
              new SourceFile(_('/foo/src/b.js'), 'abcdef', bSourceMap, false, [cSource, dSource]);

          const aSourceMap: RawSourceMap = {
            mappings: encode([[[0, 0, 0, 0], [2, 0, 0, 3], [4, 0, 0, 2], [5, 0, 0, 5]]]),
            names: [],
            sources: ['b.js'],
            version: 3
          };
          const aSource =
              new SourceFile(_('/foo/src/a.js'), 'abdecf', aSourceMap, false, [bSource]);

          expect(removeOriginalSegmentLinks(aSource.flattenedMappings)).toEqual([
            {
              generatedSegment: {line: 0, column: 0, position: 0, next: undefined},
              originalSource: dSource,
              originalSegment: {line: 0, column: 0, position: 0, next: undefined},
              name: undefined
            },
            {
              generatedSegment: {line: 0, column: 1, position: 1, next: undefined},
              originalSource: cSource,
              originalSegment: {line: 0, column: 0, position: 0, next: undefined},
              name: undefined
            },
            {
              generatedSegment: {line: 0, column: 2, position: 2, next: undefined},
              originalSource: cSource,
              originalSegment: {line: 0, column: 2, position: 2, next: undefined},
              name: undefined
            },
            {
              generatedSegment: {line: 0, column: 3, position: 3, next: undefined},
              originalSource: dSource,
              originalSegment: {line: 0, column: 1, position: 1, next: undefined},
              name: undefined
            },
            {
              generatedSegment: {line: 0, column: 4, position: 4, next: undefined},
              originalSource: cSource,
              originalSegment: {line: 0, column: 1, position: 1, next: undefined},
              name: undefined
            },
            {
              generatedSegment: {line: 0, column: 5, position: 5, next: undefined},
              originalSource: dSource,
              originalSegment: {line: 0, column: 2, position: 2, next: undefined},
              name: undefined
            },
          ]);
        });

        it('should ignore mappings to missing source files', () => {
          const bSourceMap: RawSourceMap = {
            mappings: encode([[[1, 0, 0, 0], [4, 0, 0, 3], [4, 0, 0, 6], [5, 0, 0, 7]]]),
            names: [],
            sources: ['c.js'],
            version: 3
          };
          const bSource = new SourceFile(_('/foo/src/b.js'), 'abcdef', bSourceMap, false, [null]);
          const aSourceMap: RawSourceMap = {
            mappings: encode([[[0, 0, 0, 0], [2, 0, 0, 3], [4, 0, 0, 2], [5, 0, 0, 5]]]),
            names: [],
            sources: ['b.js'],
            version: 3
          };
          const aSource =
              new SourceFile(_('/foo/src/a.js'), 'abdecf', aSourceMap, false, [bSource]);

          // These flattened mappings are just the mappings from a to b.
          // (The mappings to c are dropped since there is no source file to map to.)
          expect(removeOriginalSegmentLinks(aSource.flattenedMappings))
              .toEqual(parseMappings(aSourceMap, [bSource], [0, 7]));
        });

        /**
         * Clean out the links between original segments of each of the given `mappings`.
         *
         * @param mappings the mappings whose segments are to be cleaned.
         */
        function removeOriginalSegmentLinks(mappings: Mapping[]) {
          for (const mapping of mappings) {
            mapping.originalSegment.next = undefined;
          }
          return mappings;
        }
      });

      describe('renderFlattenedSourceMap()', () => {
        it('should convert the flattenedMappings into a raw source-map object', () => {
          const cSource = new SourceFile(_('/foo/src/c.js'), 'bcd123e', null, false, []);
          const bToCSourceMap: RawSourceMap = {
            mappings: encode([[[1, 0, 0, 0], [4, 0, 0, 3], [4, 0, 0, 6], [5, 0, 0, 7]]]),
            names: [],
            sources: ['c.js'],
            version: 3
          };
          const bSource =
              new SourceFile(_('/foo/src/b.js'), 'abcdef', bToCSourceMap, false, [cSource]);
          const aToBSourceMap: RawSourceMap = {
            mappings: encode([[[0, 0, 0, 0], [2, 0, 0, 3], [4, 0, 0, 2], [5, 0, 0, 5]]]),
            names: [],
            sources: ['b.js'],
            version: 3
          };
          const aSource =
              new SourceFile(_('/foo/src/a.js'), 'abdecf', aToBSourceMap, false, [bSource]);

          const aTocSourceMap = aSource.renderFlattenedSourceMap();
          expect(aTocSourceMap.version).toEqual(3);
          expect(aTocSourceMap.file).toEqual('a.js');
          expect(aTocSourceMap.names).toEqual([]);
          expect(aTocSourceMap.sourceRoot).toBeUndefined();
          expect(aTocSourceMap.sources).toEqual(['c.js']);
          expect(aTocSourceMap.sourcesContent).toEqual(['bcd123e']);
          expect(aTocSourceMap.mappings).toEqual(encode([
            [[1, 0, 0, 0], [2, 0, 0, 2], [3, 0, 0, 3], [3, 0, 0, 6], [4, 0, 0, 1], [5, 0, 0, 7]]
          ]));
        });

        it('should handle mappings that map from lines outside of the actual content lines', () => {
          const bSource = new SourceFile(_('/foo/src/b.js'), 'abcdef', null, false, []);
          const aToBSourceMap: RawSourceMap = {
            mappings: encode([
              [[0, 0, 0, 0], [2, 0, 0, 3], [4, 0, 0, 2], [5, 0, 0, 5]],
              [
                [0, 0, 0, 0],  // Extra mapping from a non-existent line
              ]
            ]),
            names: [],
            sources: ['b.js'],
            version: 3
          };
          const aSource =
              new SourceFile(_('/foo/src/a.js'), 'abdecf', aToBSourceMap, false, [bSource]);

          const aTocSourceMap = aSource.renderFlattenedSourceMap();
          expect(aTocSourceMap.version).toEqual(3);
          expect(aTocSourceMap.file).toEqual('a.js');
          expect(aTocSourceMap.names).toEqual([]);
          expect(aTocSourceMap.sourceRoot).toBeUndefined();
          expect(aTocSourceMap.sources).toEqual(['b.js']);
          expect(aTocSourceMap.sourcesContent).toEqual(['abcdef']);
          expect(aTocSourceMap.mappings).toEqual(aToBSourceMap.mappings);
        });
      });
    });

    describe('computeStartOfLinePositions()', () => {
      it('should compute the cumulative length of each line in the given string', () => {
        expect(computeStartOfLinePositions('')).toEqual([0]);
        expect(computeStartOfLinePositions('abc')).toEqual([0]);
        expect(computeStartOfLinePositions('\n')).toEqual([0, 1]);
        expect(computeStartOfLinePositions('\n\n')).toEqual([0, 1, 2]);
        expect(computeStartOfLinePositions('abc\n')).toEqual([0, 4]);
        expect(computeStartOfLinePositions('\nabc')).toEqual([0, 1]);
        expect(computeStartOfLinePositions('abc\ndefg')).toEqual([0, 4]);
        expect(computeStartOfLinePositions('abc\r\n')).toEqual([0, 4]);
        expect(computeStartOfLinePositions('abc\r\ndefg')).toEqual([0, 4]);
      });
    });
  });
});