Switch to TraceMap

[trace-mapping](https://github.com/jridgewell/trace-mapping) is faster, smaller, and lighter than the `source-map` package, and doesn't require WASM, manual memory management, or async/await to use.

Fixes istanbuljs#185.

README.md

@@ -13,7 +13,7 @@ const v8toIstanbul = require('v8-to-istanbul')
 // the path to the original source-file is required, as its contents are
 // used during the conversion algorithm.
 const converter = v8toIstanbul('./path-to-instrumented-file.js')
-await converter.load() // this is required due to the async source-map dependency.
+await converter.load() // this is required due to async file reading.
 // provide an array of coverage information in v8 format.
 converter.applyCoverage([
   {

index.d.ts

@@ -2,7 +2,7 @@
 
 import { Profiler } from 'inspector'
 import { CoverageMapData } from 'istanbul-lib-coverage'
-import { RawSourceMap } from 'source-map'
+import { SourceMapInput } from '@jridgewell/trace-mapping'
 
 declare type Sources =
   | {
@@ -11,7 +11,7 @@ declare type Sources =
   | {
       source: string
       originalSource: string
-      sourceMap: { sourcemap: RawSourceMap }
+      sourceMap: { sourcemap: SourceMapInput }
     }
 declare class V8ToIstanbul {
   load(): Promise<void>

lib/source.js

@@ -1,6 +1,6 @@
 const CovLine = require('./line')
 const { sliceRange } = require('./range')
-const { GREATEST_LOWER_BOUND, LEAST_UPPER_BOUND } = require('source-map').SourceMapConsumer
+const { originalPositionFor, generatedPositionFor, GREATEST_LOWER_BOUND, LEAST_UPPER_BOUND } = require('@jridgewell/trace-mapping')
 
 module.exports = class CovSource {
   constructor (sourceRaw, wrapperLength) {
@@ -102,7 +102,7 @@ module.exports = class CovSource {
     }
 
     if (start.line === end.line && start.column === end.column) {
-      end = sourceMap.originalPositionFor({
+      end = originalPositionFor(sourceMap, {
         line: lines[lines.length - 1].line,
         column: endCol - lines[lines.length - 1].startCol,
         bias: LEAST_UPPER_BOUND
@@ -168,7 +168,7 @@ function originalEndPositionFor (sourceMap, line, column) {
   // for mappings in the original-order sorted list, this will find the
   // mapping that corresponds to the one immediately after the
   // beforeEndMapping mapping.
-  const afterEndMapping = sourceMap.generatedPositionFor({
+  const afterEndMapping = generatedPositionFor(sourceMap, {
     source: beforeEndMapping.source,
     line: beforeEndMapping.line,
     column: beforeEndMapping.column + 1,
@@ -181,7 +181,7 @@ function originalEndPositionFor (sourceMap, line, column) {
       // If these don't match, it means that the call to
       // 'generatedPositionFor' didn't find any other original mappings on
       // the line we gave, so consider the binding to extend to infinity.
-      sourceMap.originalPositionFor(afterEndMapping).line !==
+      originalPositionFor(sourceMap, afterEndMapping).line !==
           beforeEndMapping.line
   ) {
     return {
@@ -192,17 +192,17 @@ function originalEndPositionFor (sourceMap, line, column) {
   }
 
   // Convert the end mapping into the real original position.
-  return sourceMap.originalPositionFor(afterEndMapping)
+  return originalPositionFor(sourceMap, afterEndMapping)
 }
 
 function originalPositionTryBoth (sourceMap, line, column) {
-  let original = sourceMap.originalPositionFor({
+  let original = originalPositionFor(sourceMap, {
     line,
     column,
     bias: GREATEST_LOWER_BOUND
   })
   if (original.line === null) {
-    original = sourceMap.originalPositionFor({
+    original = originalPositionFor(sourceMap, {
       line,
       column,
       bias: LEAST_UPPER_BOUND
@@ -220,7 +220,7 @@ function originalPositionTryBoth (sourceMap, line, column) {
   //     }  else { ... }
   //  ^  ^
   // l5  l3
-  const min = sourceMap.originalPositionFor({
+  const min = originalPositionFor(sourceMap, {
     line,
     column: 0,
     bias: GREATEST_LOWER_BOUND

lib/v8-to-istanbul.js

@@ -15,7 +15,7 @@ try {
 } catch (_err) {
   // most likely we're on an older version of Node.js.
 }
-const { SourceMapConsumer } = require('source-map')
+const { TraceMap } = require('@jridgewell/trace-mapping')
 const isOlderNode10 = /^v10\.(([0-9]\.)|(1[0-5]\.))/u.test(process.version)
 const isNode8 = /^v8\./.test(process.version)
 
@@ -53,7 +53,7 @@ module.exports = class V8ToIstanbul {
 
     if (this.rawSourceMap) {
       if (this.rawSourceMap.sourcemap.sources.length > 1) {
-        this.sourceMap = await new SourceMapConsumer(this.rawSourceMap.sourcemap)
+        this.sourceMap = new TraceMap(this.rawSourceMap.sourcemap)
         if (!this.sourceMap.sourcesContent) {
           this.sourceMap.sourcesContent = await this.sourcesContentFromSources()
         }
@@ -62,7 +62,7 @@ module.exports = class V8ToIstanbul {
       } else {
         const candidatePath = this.rawSourceMap.sourcemap.sources.length >= 1 ? this.rawSourceMap.sourcemap.sources[0] : this.rawSourceMap.sourcemap.file
         this.path = this._resolveSource(this.rawSourceMap, candidatePath || this.path)
-        this.sourceMap = await new SourceMapConsumer(this.rawSourceMap.sourcemap)
+        this.sourceMap = new TraceMap(this.rawSourceMap.sourcemap)
 
         let originalRawSource
         if (this.sources.sourceMap && this.sources.sourceMap.sourcemap && this.sources.sourceMap.sourcemap.sourcesContent && this.sources.sourceMap.sourcemap.sourcesContent.length === 1) {
@@ -102,10 +102,7 @@ module.exports = class V8ToIstanbul {
   }
 
   destroy () {
-    if (this.sourceMap) {
-      this.sourceMap.destroy()
-      this.sourceMap = undefined
-    }
+    this.sourceMap = undefined
   }
 
   _resolveSource (rawSourceMap, sourcePath) {

package.json

@@ -25,15 +25,16 @@
   "author": "Ben Coe <ben@npmjs.com>",
   "license": "ISC",
   "dependencies": {
+    "@jridgewell/trace-mapping": "0.3.6",
     "@types/istanbul-lib-coverage": "^2.0.1",
-    "convert-source-map": "^1.6.0",
-    "source-map": "^0.7.3"
+    "convert-source-map": "^1.6.0"
   },
   "devDependencies": {
     "@types/node": "^16.0.0",
     "c8": "^7.2.1",
     "semver": "^7.3.2",
     "should": "13.2.3",
+    "source-map": "^0.7.3",
     "standard": "^16.0.4",
     "tap": "^15.1.6"
   },

test/source.js

@@ -1,7 +1,7 @@
 /* global describe, it */
 
 const CovSource = require('../lib/source')
-const { SourceMapConsumer } = require('source-map')
+const { TraceMap } = require('@jridgewell/trace-mapping')
 
 require('tap').mochaGlobals()
 require('should')
@@ -45,7 +45,7 @@ describe('Source', () => {
       new CovSource(sourceRaw, 0).should.ok()
     })
 
-    it('range crossing two sourcemaps', async () => {
+    it('range crossing two sourcemaps', () => {
       const sourceRaw = `\
 (() => {
   // hello.ts
@@ -59,7 +59,7 @@ describe('Source', () => {
 //# sourceMappingURL=greet.js.map\
 `
       const source = new CovSource(sourceRaw, 0)
-      const sourceMap = await new SourceMapConsumer({
+      const sourceMap = new TraceMap({
         version: 3,
         sources: ['../hello.ts', '../greet.ts'],
         sourcesContent: ['export function hello() {\r\n  console.log("hello world")\r\n}', 'import {hello} from "./hello"\r\n\r\nhello()\r\n'],