Switch to GenMapping for sourcemap generation

[`gen-mapping`](https://github.com/jridgewell/gen-mapping) is faster, smaller, and lighter sourcemap generation library. This also exposes a new `decodedMap` property on the result object. Decoded maps are free to create (it's a shallow clone of the `GenMapping` instance), and passing them to `@jridgewell/trace-mapping` is copy-free. With Babel [recently](babel/babel#14497) adding a `decodedMap` field, a dev could pass from the Babel transpilation to Terser without any added memory use for sourcemaps. And if there's a multi stage build process, a dev could use `@ampproject/remapping` to remap Babel, Terser, and (eg) a bundler's outputs without having to feed input maps into each stage.
jridgewell · Apr 30, 2022 · d23354e · d23354e
1 parent 423b304
commit d23354e
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Showing 10 changed files with 112 additions and 85 deletions.
diff --git a/lib/minify.js b/lib/minify.js
@@ -271,18 +271,15 @@ async function minify(files, options, _fs_module) {
     }
     if (!HOP(options.format, "code") || options.format.code) {
         if (options.sourceMap) {
-            options.format.source_map = await SourceMap({
+            if (options.sourceMap.includeSources && files instanceof AST_Toplevel) {
+                throw new Error("original source content unavailable");
+            }
+            options.format.source_map = SourceMap({
                 file: options.sourceMap.filename,
                 orig: options.sourceMap.content,
-                root: options.sourceMap.root
+                root: options.sourceMap.root,
+                files: options.sourceMap.includeSources ? files : null,
             });
-            if (options.sourceMap.includeSources) {
-                if (files instanceof AST_Toplevel) {
-                    throw new Error("original source content unavailable");
-                } else for (var name in files) if (HOP(files, name)) {
-                    options.format.source_map.get().setSourceContent(name, files[name]);
-                }
-            }
         }
         delete options.format.ast;
         delete options.format.code;
@@ -291,11 +288,21 @@ async function minify(files, options, _fs_module) {
         toplevel.print(stream);
         result.code = stream.get();
         if (options.sourceMap) {
-            if(options.sourceMap.asObject) {
-                result.map = options.format.source_map.get().toJSON();
-            } else {
-                result.map = options.format.source_map.toString();
-            }
+            Object.defineProperty(result, "map", {
+                configurable: true,
+                enumerable: true,
+                get() {
+                    const map = options.format.source_map.getEncoded();
+                    return (result.map = options.sourceMap.asObject ? map : JSON.stringify(map));
+                },
+                set(value) {
+                    Object.defineProperty(result, "map", {
+                        value,
+                        writable: true,
+                    });
+                }
+            });
+            result.decodedMap = options.format.source_map.getDecoded();
             if (options.sourceMap.url == "inline") {
                 var sourceMap = typeof result.map === "object" ? JSON.stringify(result.map) : result.map;
                 result.code += "\n//# sourceMappingURL=data:application/json;charset=utf-8;base64," + to_base64(sourceMap);
@@ -310,9 +317,6 @@ async function minify(files, options, _fs_module) {
             options.nameCache.props = cache_to_json(options.mangle.properties.cache);
         }
     }
-    if (options.format && options.format.source_map) {
-        options.format.source_map.destroy();
-    }
     if (timings) {
         timings.end = Date.now();
         result.timings = {

diff --git a/lib/sourcemap.js b/lib/sourcemap.js
@@ -43,34 +43,37 @@
 
 "use strict";
 
-import MOZ_SourceMap from "source-map";
+import {GenMapping, maybeAddMapping, toDecodedMap, toEncodedMap, setSourceContent} from "@jridgewell/gen-mapping";
 import {AnyMap, originalPositionFor} from "@jridgewell/trace-mapping";
-import {defaults} from "./utils/index.js";
+import {defaults, HOP} from "./utils/index.js";
 
 // a small wrapper around source-map and @jridgewell/trace-mapping
 function SourceMap(options) {
     options = defaults(options, {
         file : null,
         root : null,
         orig : null,
-
-        orig_line_diff : 0,
-        dest_line_diff : 0,
+        files: {},
     });
 
     var orig_map;
-    var generator = new MOZ_SourceMap.SourceMapGenerator({
+    var generator = new GenMapping({
         file       : options.file,
         sourceRoot : options.root
     });
 
+    let sourcesContent = {__proto__: null};
+    let files = options.files;
+    for (var name in files) if (HOP(files, name)) {
+        sourcesContent[name] = files[name];
+    }
     if (options.orig) {
         orig_map = new AnyMap(options.orig);
         if (orig_map.sourcesContent) {
             orig_map.resolvedSources.forEach(function(source, i) {
-                var sourceContent = orig_map.sourcesContent[i];
-                if (sourceContent) {
-                    generator.setSourceContent(source, sourceContent);
+                var content = orig_map.sourcesContent[i];
+                if (content) {
+                    sourcesContent[source] = content;
                 }
             });
         }
@@ -90,19 +93,27 @@ function SourceMap(options) {
             orig_col = info.column;
             name = info.name || name;
         }
-        generator.addMapping({
-            generated : { line: gen_line + options.dest_line_diff, column: gen_col },
-            original  : { line: orig_line + options.orig_line_diff, column: orig_col },
+        maybeAddMapping(generator, {
+            generated : { line: gen_line, column: gen_col },
+            original  : { line: orig_line, column: orig_col },
             source    : source,
             name      : name
         });
+        setSourceContent(generator, source, sourcesContent[source]);
+    }
+
+    function clean(map) {
+        const allNull = map.sourcesContent.every(c => c == null);
+        if (allNull) delete map.sourcesContent;
+        if (map.file === undefined) delete map.file;
+        if (map.sourceRoot === undefined) delete map.sourceRoot;
+        return map;
     }
 
     return {
-        add        : add,
-        get        : function() { return generator; },
-        toString   : function() { return generator.toString(); },
-        destroy    : function() {}
+        add             : add,
+        getDecoded      : function() { return clean(toDecodedMap(generator)); },
+        getEncoded      : function() { return clean(toEncodedMap(generator)); },
     };
 }
 

diff --git a/package-lock.json b/package-lock.json
diff --git a/package.json b/package.json
@@ -43,10 +43,10 @@
     "main.js"
   ],
   "dependencies": {
+    "@jridgewell/gen-mapping": "^0.3.0",
     "@jridgewell/trace-mapping": "^0.3.5",
     "acorn": "^8.5.0",
     "commander": "^2.20.0",
-    "source-map": "~0.8.0-beta.0",
     "source-map-support": "~0.5.20"
   },
   "devDependencies": {

diff --git a/test/input/issue-505/output.js b/test/input/issue-505/output.js
diff --git a/test/input/issue-520/output.js b/test/input/issue-520/output.js
diff --git a/test/input/source-maps/expect.js b/test/input/source-maps/expect.js
diff --git a/test/mocha/cli-2.js b/test/mocha/cli-2.js
@@ -21,7 +21,7 @@ describe("bin/terser (2)", function() {
 
             assert.strictEqual(stdout, [
                 '"use strict";var foo=function foo(x){return"foo "+x};console.log(foo("bar"));',
-                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbImluZGV4LmpzIl0sIm5hbWVzIjpbImZvbyIsIngiLCJjb25zb2xlIiwibG9nIl0sIm1hcHBpbmdzIjoiYUFBQSxJQUFJQSxJQUFNLFNBQU5BLElBQU1DLEdBQUEsTUFBSyxPQUFTQSxHQUN4QkMsUUFBUUMsSUFBSUgsSUFBSSJ9",
+                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJuYW1lcyI6WyJmb28iLCJ4IiwiY29uc29sZSIsImxvZyJdLCJzb3VyY2VzIjpbImluZGV4LmpzIl0sIm1hcHBpbmdzIjoiYUFBQSxJQUFJQSxJQUFNLFNBQU5BLElBQU1DLEdBQUEsTUFBSyxPQUFTQSxHQUN4QkMsUUFBUUMsSUFBSUgsSUFBSSJ9",
                 ""
             ].join("\n"));
             done();
@@ -46,7 +46,7 @@ describe("bin/terser (2)", function() {
 
             assert.strictEqual(stdout, [
                 'function foo(){return function(){console.log("PASS")}}foo()();',
-                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInRlc3QvaW5wdXQvaXNzdWUtMjMxMC9pbnB1dC5qcyJdLCJuYW1lcyI6WyJmb28iLCJjb25zb2xlIiwibG9nIiwiZiJdLCJtYXBwaW5ncyI6IkFBQUEsU0FBU0EsTUFDTCxPQUFPLFdBQ0hDLFFBQVFDLElBQUksU0FLUkYsS0FDUkcifQ==",
+                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJuYW1lcyI6WyJmb28iLCJjb25zb2xlIiwibG9nIiwiZiJdLCJzb3VyY2VzIjpbInRlc3QvaW5wdXQvaXNzdWUtMjMxMC9pbnB1dC5qcyJdLCJtYXBwaW5ncyI6IkFBQUEsU0FBU0EsTUFDTCxPQUFPLFdBQ0hDLFFBQVFDLElBQUksU0FLUkYsS0FDUkcifQ==",
                 ""
             ].join("\n"));
             done();

diff --git a/test/mocha/minify.js b/test/mocha/minify.js
@@ -321,7 +321,7 @@ describe("minify", function() {
             });
             var code = result.code;
             assert.strictEqual(code, "var a=function(n){return n};\n" +
-                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIjAiXSwibmFtZXMiOlsiYSIsImZvbyJdLCJtYXBwaW5ncyI6IkFBQUEsSUFBSUEsRUFBSSxTQUFTQyxHQUFPLE9BQU9BIn0=");
+                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJuYW1lcyI6WyJhIiwiZm9vIl0sInNvdXJjZXMiOlsiMCJdLCJtYXBwaW5ncyI6IkFBQUEsSUFBSUEsRUFBSSxTQUFTQyxHQUFPLE9BQU9BIn0=");
         });
         it("should not append source map to output js when sourceMapInline is not enabled", async function() {
             var result = await minify("var a = function(foo) { return foo; };");

diff --git a/test/mocha/sourcemaps.js b/test/mocha/sourcemaps.js
@@ -1,11 +1,11 @@
 import assert from "assert";
 import { readFileSync } from "fs";
-import source_map_module from "source-map"
+import source_map_module from "source-map";
 import { assertCodeWithInlineMapEquals } from "./utils.js";
 import { to_ascii } from "../../lib/minify.js";
 import { minify } from "../../main.js";
 
-const { SourceMapConsumer } = source_map_module
+const { SourceMapConsumer } = source_map_module;
 
 function read(path) {
     return readFileSync(path, "utf8");
@@ -96,7 +96,12 @@ describe("sourcemaps", function() {
         });
         if (result.error) throw result.error;
         assert.strictEqual(result.code, "({}).wat([]);");
-        assert.strictEqual(result.map, '{"version":3,"sources":["0"],"names":["wat"],"mappings":"CAAU,IACNA,IAAI"}');
+        assert.deepStrictEqual(JSON.parse(result.map), {
+            version: 3,
+            sources: ["0"],
+            names: ["wat"],
+            mappings: "CAAU,IACNA,IAAI",
+        });
     });
     it("Should mark class literals", async function() {
         var result = await minify([
@@ -109,7 +114,12 @@ describe("sourcemaps", function() {
         });
         if (result.error) throw result.error;
         assert.strictEqual(result.code, "(class{}).wat(class{});");
-        assert.strictEqual(result.map, '{"version":3,"sources":["0"],"names":["wat"],"mappings":"CACU,SACNA,IAFJ"}');
+        assert.deepStrictEqual(JSON.parse(result.map), {
+            version: 3,
+            sources: ["0"],
+            names: ["wat"],
+            mappings: "CACU,SACNA,IAFJ",
+        });
     });
     it("Should give correct sourceRoot", async function() {
         var code = "console.log(42);";
@@ -120,7 +130,13 @@ describe("sourcemaps", function() {
         });
         if (result.error) throw result.error;
         assert.strictEqual(result.code, code);
-        assert.strictEqual(result.map, '{"version":3,"sources":["0"],"names":["console","log"],"mappings":"AAAAA,QAAQC,IAAI","sourceRoot":"//foo.bar/"}');
+        assert.deepStrictEqual(JSON.parse(result.map), {
+            version: 3,
+            sources: ["0"],
+            names: ["console","log"],
+            mappings: "AAAAA,QAAQC,IAAI",
+            sourceRoot: "//foo.bar/",
+        });
     });
     it("Should return source map as object when asObject is given", async function() {
         var code = "console.log(42);";
@@ -131,7 +147,12 @@ describe("sourcemaps", function() {
         });
         if (result.error) throw result.error;
         assert.strictEqual(result.code, code);
-        assert.deepStrictEqual(result.map, {"version":3,"sources":["0"],"names":["console","log"],"mappings":"AAAAA,QAAQC,IAAI"});
+        assert.deepStrictEqual(result.map, {
+            version: 3,
+            sources: ["0"],
+            names: ["console","log"],
+            mappings: "AAAAA,QAAQC,IAAI",
+        });
     });
 
     it("Should grab names from methods and properties correctly", async () => {
@@ -191,8 +212,8 @@ describe("sourcemaps", function() {
             if (result.error) throw result.error;
             var map = JSON.parse(result.map);
             assert.equal(map.file, "simple.min.js");
-            assert.equal(map.sourcesContent.length, 1);
-            assert.equal(map.sourcesContent[0], 'let foo = x => "foo " + x;\nconsole.log(foo("bar"));');
+            assert.deepEqual(map.sources, ["index.js"]);
+            assert.deepEqual(map.sourcesContent, ['let foo = x => "foo " + x;\nconsole.log(foo("bar"));']);
         });
         it("Should process inline source map", async function() {
             var result = await minify(read("./test/input/issue-520/input.js"), {