[cli] Avoid SourceMapGenerator for simple map concatenation (#14479)

packages/babel-cli/package.json

@@ -24,14 +24,13 @@
     "compiler"
   ],
   "dependencies": {
-    "@jridgewell/trace-mapping": "^0.3.4",
+    "@jridgewell/trace-mapping": "^0.3.8",
     "commander": "^4.0.1",
     "convert-source-map": "^1.1.0",
     "fs-readdir-recursive": "^1.1.0",
     "glob": "^7.0.0",
     "make-dir": "condition:BABEL_8_BREAKING ? : ^2.1.0",
-    "slash": "condition:BABEL_8_BREAKING ? ^3.0.0 : ^2.0.0",
-    "source-map": "^0.5.0"
+    "slash": "condition:BABEL_8_BREAKING ? ^3.0.0 : ^2.0.0"
   },
   "optionalDependencies": {
     "@nicolo-ribaudo/chokidar-2": "condition:BABEL_8_BREAKING ? : 2.1.8-no-fsevents.3",

packages/babel-cli/src/babel/file.ts

@@ -1,6 +1,5 @@
 import convertSourceMap from "convert-source-map";
-import { TraceMap, eachMapping } from "@jridgewell/trace-mapping";
-import sourceMap from "source-map";
+import { AnyMap, encodedMap } from "@jridgewell/trace-mapping";
 import slash from "slash";
 import path from "path";
 import fs from "fs";
@@ -19,66 +18,66 @@ export default async function ({
   babelOptions,
 }: CmdOptions): Promise<void> {
   function buildResult(fileResults: Array<any>): CompilationOutput {
-    const map = new sourceMap.SourceMapGenerator({
-      file:
-        cliOptions.sourceMapTarget ||
-        path.basename(cliOptions.outFile || "") ||
-        "stdout",
-      sourceRoot: babelOptions.sourceRoot,
-    });
+    const mapSections = [];
 
     let code = "";
     let offset = 0;
 
     for (const result of fileResults) {
       if (!result) continue;
 
-      code += result.code + "\n";
-
-      if (result.map) {
-        const consumer = new TraceMap(result.map);
-
-        eachMapping(consumer, mapping => {
-          map.addMapping({
-            generated: {
-              line: mapping.generatedLine + offset,
-              column: mapping.generatedColumn,
-            },
-            source: mapping.source,
-            original:
-              mapping.source == null
-                ? null
-                : {
-                    line: mapping.originalLine,
-                    column: mapping.originalColumn,
-                  },
-          });
-        });
-
-        const { resolvedSources, sourcesContent } = consumer;
-        sourcesContent?.forEach((content, i) => {
-          if (content === null) return;
-          map.setSourceContent(resolvedSources[i], content);
-        });
+      mapSections.push({
+        offset: { line: offset, column: 0 },
+        map: result.map || emptyMap(),
+      });
 
-        offset = code.split("\n").length - 1;
-      }
+      code += result.code + "\n";
+      offset += countNewlines(result.code) + 1;
     }
 
+    const map = new AnyMap({
+      version: 3,
+      file:
+        cliOptions.sourceMapTarget ||
+        path.basename(cliOptions.outFile || "") ||
+        "stdout",
+      sections: mapSections,
+    });
+    // For some reason, the spec doesn't allow sourceRoot when constructing a
+    // sectioned sorucemap. But AllMap returns a regular sourcemap, we can
+    // freely add to with a sourceRoot.
+    map.sourceRoot = babelOptions.sourceRoot;
+
     // add the inline sourcemap comment if we've either explicitly asked for inline source
     // maps, or we've requested them without any output file
     if (
       babelOptions.sourceMaps === "inline" ||
       (!cliOptions.outFile && babelOptions.sourceMaps)
     ) {
-      code += "\n" + convertSourceMap.fromObject(map).toComment();
+      code += "\n" + convertSourceMap.fromObject(encodedMap(map)).toComment();
     }
 
     return {
       map: map,
       code: code,
     };
   }
+  function countNewlines(code: string): number {
+    let count = 0;
+    let index = -1;
+    while ((index = code.indexOf("\n", index + 1)) !== -1) {
+      count++;
+    }
+    return count;
+  }
+  function emptyMap() {
+    return {
+      version: 3,
+      names: [],
+      sources: [],
+      mappings: [],
+    };
+  }
 
   function output(fileResults: Array<string>): void {
     const result = buildResult(fileResults);
@@ -90,7 +89,7 @@ export default async function ({
       if (babelOptions.sourceMaps && babelOptions.sourceMaps !== "inline") {
         const mapLoc = cliOptions.outFile + ".map";
         result.code = util.addSourceMappingUrl(result.code, mapLoc);
-        fs.writeFileSync(mapLoc, JSON.stringify(result.map));
+        fs.writeFileSync(mapLoc, JSON.stringify(encodedMap(result.map)));
       }
 
       fs.writeFileSync(cliOptions.outFile, result.code);

packages/babel-cli/test/fixtures/babel/stdin --source-maps inline/stdout.txt

@@ -5,4 +5,4 @@ arr.map(function (x) {
 });
 //# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInN0ZGluIl0sIm5hbWVzIjpbImFyciIsIm1hcCIsIngiXSwibWFwcGluZ3MiOiI7O0FBQUFBLEdBQUcsQ0FBQ0MsR0FBSixDQUFRLFVBQUFDLENBQUM7QUFBQSxTQUFJQSxDQUFDLEdBQUdBLENBQVI7QUFBQSxDQUFUIiwic291cmNlc0NvbnRlbnQiOlsiYXJyLm1hcCh4ID0+IHggKiB4KTsiXX0=
 
-//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6IiIsImZpbGUiOiJzdGRvdXQifQ==
+//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoic3Rkb3V0IiwibmFtZXMiOltdLCJzb3VyY2VzIjpbXSwic291cmNlc0NvbnRlbnQiOltdLCJtYXBwaW5ncyI6IiJ9

packages/babel-core/package.json

@@ -67,7 +67,7 @@
   "devDependencies": {
     "@babel/helper-transform-fixture-test-runner": "workspace:^",
     "@babel/plugin-transform-modules-commonjs": "workspace:^",
-    "@jridgewell/trace-mapping": "^0.3.4",
+    "@jridgewell/trace-mapping": "^0.3.8",
     "@types/convert-source-map": "^1.5.1",
     "@types/debug": "^4.1.0",
     "@types/resolve": "^1.3.2",

packages/babel-generator/package.json

@@ -26,7 +26,7 @@
   "devDependencies": {
     "@babel/helper-fixtures": "workspace:^",
     "@babel/parser": "workspace:^",
-    "@jridgewell/trace-mapping": "^0.3.4",
+    "@jridgewell/trace-mapping": "^0.3.8",
     "@types/jsesc": "^2.5.0",
     "@types/source-map": "^0.5.0",
     "charcodes": "^0.2.0"

packages/babel-helper-transform-fixture-test-runner/package.json

@@ -19,7 +19,7 @@
     "@babel/core": "workspace:^",
     "@babel/helper-check-duplicate-nodes": "workspace:^",
     "@babel/helper-fixtures": "workspace:^",
-    "@jridgewell/trace-mapping": "^0.3.4",
+    "@jridgewell/trace-mapping": "^0.3.8",
     "quick-lru": "5.1.0",
     "regenerator-runtime": "^0.13.7"
   },

yarn.lock

@@ -202,7 +202,7 @@ __metadata:
   dependencies:
     "@babel/core": "workspace:^"
     "@babel/helper-fixtures": "workspace:^"
-    "@jridgewell/trace-mapping": ^0.3.4
+    "@jridgewell/trace-mapping": ^0.3.8
     "@nicolo-ribaudo/chokidar-2": "condition:BABEL_8_BREAKING ? : 2.1.8-no-fsevents.3"
     chokidar: ^3.4.0
     commander: ^4.0.1
@@ -212,7 +212,6 @@ __metadata:
     make-dir: "condition:BABEL_8_BREAKING ? : ^2.1.0"
     rimraf: ^3.0.0
     slash: "condition:BABEL_8_BREAKING ? ^3.0.0 : ^2.0.0"
-    source-map: ^0.5.0
   peerDependencies:
     "@babel/core": ^7.0.0-0
   dependenciesMeta:
@@ -335,7 +334,7 @@ __metadata:
     "@babel/template": "workspace:^"
     "@babel/traverse": "workspace:^"
     "@babel/types": "workspace:^"
-    "@jridgewell/trace-mapping": ^0.3.4
+    "@jridgewell/trace-mapping": ^0.3.8
     "@types/convert-source-map": ^1.5.1
     "@types/debug": ^4.1.0
     "@types/resolve": ^1.3.2
@@ -457,7 +456,7 @@ __metadata:
     "@babel/helper-fixtures": "workspace:^"
     "@babel/parser": "workspace:^"
     "@babel/types": "workspace:^"
-    "@jridgewell/trace-mapping": ^0.3.4
+    "@jridgewell/trace-mapping": ^0.3.8
     "@types/jsesc": ^2.5.0
     "@types/source-map": ^0.5.0
     charcodes: ^0.2.0
@@ -957,7 +956,7 @@ __metadata:
     "@babel/core": "workspace:^"
     "@babel/helper-check-duplicate-nodes": "workspace:^"
     "@babel/helper-fixtures": "workspace:^"
-    "@jridgewell/trace-mapping": ^0.3.4
+    "@jridgewell/trace-mapping": ^0.3.8
     "@types/jest": ^27.4.1
     quick-lru: 5.1.0
     regenerator-runtime: ^0.13.7
@@ -4085,13 +4084,13 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@jridgewell/trace-mapping@npm:^0.3.0, @jridgewell/trace-mapping@npm:^0.3.4":
-  version: 0.3.4
-  resolution: "@jridgewell/trace-mapping@npm:0.3.4"
+"@jridgewell/trace-mapping@npm:^0.3.0, @jridgewell/trace-mapping@npm:^0.3.8":
+  version: 0.3.8
+  resolution: "@jridgewell/trace-mapping@npm:0.3.8"
   dependencies:
     "@jridgewell/resolve-uri": ^3.0.3
     "@jridgewell/sourcemap-codec": ^1.4.10
-  checksum: ab8bce84bbbc8c34f3ba8325ed926f8f2d3098983c10442a80c55764c4eb6e47d5b92d8ff20a0dd868c3e76a3535651fd8a0138182c290dbfc8396195685c37b
+  checksum: 4b46f28c785133773de521677983186dfe7ed80872bee57b73624527e345954139ea45dfb7551a5f04de1773dc9501b896554a8f1c9e1c44ab2146a3c66b6fda
   languageName: node
   linkType: hard