Add getCombinedSourceMap in transform plugin context (#2983)

docs/05-plugin-development.md

@@ -414,6 +414,10 @@ Use the second form if you need to add additional properties to your warning obj
 
 The `position` argument is a character index where the warning was raised. If present, Rollup will augment the warning object with `pos`, `loc` (a standard `{ file, line, column }` object) and `frame` (a snippet of code showing the error).
 
+### `this.getCombinedSourceMap() => SourceMap`
+
+Get the combined source maps of all previous plugins. This context function can only be used in [`transform`](guide/en/#transform) plugin hook.
+
 ### Deprecated Context Functions
 
 ☢️ These context utility functions have been deprecated and may be removed in a future Rollup version.

src/Chunk.ts

@@ -23,7 +23,7 @@ import {
 } from './rollup/types';
 import { Addons } from './utils/addons';
 import { toBase64 } from './utils/base64';
-import collapseSourcemaps from './utils/collapseSourcemaps';
+import { collapseSourcemaps } from './utils/collapseSourcemaps';
 import { deconflictChunk } from './utils/deconflictChunk';
 import { error } from './utils/error';
 import { sortByExecutionOrder } from './utils/executionOrder';

src/utils/collapseSourcemaps.ts

@@ -1,5 +1,6 @@
 import { DecodedSourceMap, SourceMap } from 'magic-string';
 import Chunk from '../Chunk';
+import Graph from '../Graph';
 import Module from '../Module';
 import {
 	DecodedSourceMapOrMissing,
@@ -145,20 +146,13 @@ class Link {
 	}
 }
 
-export default function collapseSourcemaps(
-	bundle: Chunk,
-	file: string,
-	map: DecodedSourceMap,
-	modules: Module[],
-	bundleSourcemapChain: DecodedSourceMapOrMissing[],
-	excludeContent: boolean
-) {
-	function linkMap(source: Source | Link, map: DecodedSourceMapOrMissing) {
+function linkMapper(graph: Graph) {
+	return function linkMap(source: Source | Link, map: DecodedSourceMapOrMissing) {
 		if (map.mappings) {
 			return new Link(map, [source]);
 		}
 
-		bundle.graph.warn({
+		graph.warn({
 			code: 'SOURCEMAP_BROKEN',
 			message: `Sourcemap is likely to be incorrect: a plugin${
 				map.plugin ? ` ('${map.plugin}')` : ``
@@ -174,34 +168,55 @@ export default function collapseSourcemaps(
 			},
 			[source]
 		);
+	};
+}
+
+function unionSourcemaps(
+	id: string,
+	originalCode: string,
+	originalSourcemap: ExistingDecodedSourceMap | null,
+	sourcemapChain: DecodedSourceMapOrMissing[],
+	linkMap: (source: Source | Link, map: DecodedSourceMapOrMissing) => Link
+) {
+	let source: Source | Link;
+	if (!originalSourcemap) {
+		source = new Source(id, originalCode);
+	} else {
+		const sources = originalSourcemap.sources;
+		const sourcesContent = originalSourcemap.sourcesContent || [];
+
+		// TODO indiscriminately treating IDs and sources as normal paths is probably bad.
+		const directory = dirname(id) || '.';
+		const sourceRoot = originalSourcemap.sourceRoot || '.';
+
+		const baseSources = sources.map(
+			(source, i) => new Source(resolve(directory, sourceRoot, source), sourcesContent[i])
+		);
+		source = new Link(originalSourcemap, baseSources);
 	}
+	return sourcemapChain.reduce(linkMap, source);
+}
 
+export function collapseSourcemaps(
+	bundle: Chunk,
+	file: string,
+	map: DecodedSourceMap,
+	modules: Module[],
+	bundleSourcemapChain: DecodedSourceMapOrMissing[],
+	excludeContent: boolean
+) {
+	const linkMap = linkMapper(bundle.graph);
 	const moduleSources = modules
 		.filter(module => !module.excludeFromSourcemap)
-		.map(module => {
-			let source: Source | Link;
-			const originalSourcemap = module.originalSourcemap;
-			if (!originalSourcemap) {
-				source = new Source(module.id, module.originalCode);
-			} else {
-				const sources = originalSourcemap.sources;
-				const sourcesContent = originalSourcemap.sourcesContent || [];
-
-				// TODO indiscriminately treating IDs and sources as normal paths is probably bad.
-				const directory = dirname(module.id) || '.';
-				const sourceRoot = originalSourcemap.sourceRoot || '.';
-
-				const baseSources = sources.map(
-					(source, i) => new Source(resolve(directory, sourceRoot, source), sourcesContent[i])
-				);
-
-				source = new Link(originalSourcemap, baseSources);
-			}
-
-			source = module.sourcemapChain.reduce(linkMap, source);
-
-			return source;
-		});
+		.map(module =>
+			unionSourcemaps(
+				module.id,
+				module.originalCode,
+				module.originalSourcemap,
+				module.sourcemapChain,
+				linkMap
+			)
+		);
 
 	// DecodedSourceMap (from magic-string) uses a number[] instead of the more
 	// correct SourceMapSegment tuples. Cast it here to gain type safety.
@@ -221,3 +236,25 @@ export default function collapseSourcemaps(
 
 	return new SourceMap({ file, sources, sourcesContent, names, mappings });
 }
+
+export function collapseSourcemap(
+	graph: Graph,
+	id: string,
+	originalCode: string,
+	originalSourcemap: ExistingDecodedSourceMap,
+	sourcemapChain: DecodedSourceMapOrMissing[]
+) {
+	if (!sourcemapChain.length) {
+		return originalSourcemap;
+	}
+
+	const source = unionSourcemaps(
+		id,
+		originalCode,
+		originalSourcemap,
+		sourcemapChain,
+		linkMapper(graph)
+	) as Link;
+
+	return source.traceMappings();
+}

src/utils/transform.ts

@@ -1,10 +1,12 @@
+import MagicString, { DecodedSourceMap, SourceMap } from 'magic-string';
 import Graph from '../Graph';
 import Module from '../Module';
 import {
 	Asset,
 	DecodedSourceMapOrMissing,
 	EmitAsset,
 	EmittedChunk,
+	ExistingDecodedSourceMap,
 	Plugin,
 	PluginCache,
 	PluginContext,
@@ -15,6 +17,7 @@ import {
 	TransformSourceDescription
 } from '../rollup/types';
 import { createTransformEmitAsset } from './assetHooks';
+import { collapseSourcemap } from './collapseSourcemaps';
 import { decodedSourcemap } from './decodedSourcemap';
 import { augmentCodeLocation, error } from './error';
 import { dirname, resolve } from './path';
@@ -28,7 +31,7 @@ export default function transform(
 	const id = module.id;
 	const sourcemapChain: DecodedSourceMapOrMissing[] = [];
 
-	const originalSourcemap = source.map === null ? null : decodedSourcemap(source.map);
+	let originalSourcemap = source.map === null ? null : decodedSourcemap(source.map);
 	const baseEmitAsset = graph.pluginDriver.emitAsset;
 	const originalCode = source.code;
 	let ast = source.ast;
@@ -159,6 +162,27 @@ export default function transform(
 								setAssetSourceErr = err;
 							}
 						}
+					},
+					getCombinedSourceMap() {
+						const combinedMap = collapseSourcemap(
+							graph,
+							id,
+							originalCode,
+							originalSourcemap as ExistingDecodedSourceMap,
+							sourcemapChain
+						);
+						if (!combinedMap) {
+							const magicString = new MagicString(originalCode);
+							return magicString.generateMap({ includeContent: true, hires: true, source: id });
+						}
+						if (originalSourcemap !== combinedMap) {
+							originalSourcemap = { version: 3, ...combinedMap };
+							sourcemapChain.length = 0;
+						}
+						return new SourceMap({
+							...combinedMap,
+							file: null as any
+						} as DecodedSourceMap);
 					}
 				};
 			}

test/sourcemaps/samples/combined-sourcemap-with-loader/_config.js

@@ -0,0 +1,97 @@
+const fs = require('fs');
+const buble = require('buble');
+const MagicString = require('magic-string');
+const assert = require('assert');
+const getLocation = require('../../getLocation');
+const SourceMapConsumer = require('source-map').SourceMapConsumer;
+
+module.exports = {
+	description: 'get combined sourcemap in transforming with loader',
+	options: {
+		plugins: [
+			{
+				load(id) {
+					const code = fs.readFileSync(id, 'utf-8');
+					const out = buble.transform(code, {
+						transforms: { modules: false },
+						sourceMap: true,
+						source: id
+					});
+
+					return { code: out.code, map: out.map };
+				}
+			},
+			{
+				transform(code, id) {
+					const sourcemap = this.getCombinedSourceMap();
+					const smc = new SourceMapConsumer(sourcemap);
+					const s = new MagicString(code);
+
+					if (/foo.js$/.test(id)) {
+						testFoo(code, smc);
+
+						s.prepend('console.log("foo start");\n\n');
+						s.append('\nconsole.log("foo end");');
+					} else {
+						testMain(code, smc);
+
+						s.appendRight(code.indexOf('console'), 'console.log("main start");\n\n');
+						s.append('\nconsole.log("main end");');
+					}
+
+					return {
+						code: s.toString(),
+						map: s.generateMap({ hires: true })
+					};
+				}
+			},
+			{
+				transform(code, id) {
+					const sourcemap = this.getCombinedSourceMap();
+					const smc = new SourceMapConsumer(sourcemap);
+					const s = new MagicString(code);
+
+					if (/foo.js$/.test(id)) {
+						testFoo(code, smc);
+
+						s.prepend('console.log("-- foo ---");\n\n');
+						s.append('\nconsole.log("-----");');
+					} else {
+						testMain(code, smc);
+
+						s.appendRight(code.indexOf('console'), 'console.log("-- main ---");\n\n');
+						s.append('\nconsole.log("-----");');
+					}
+
+					return {
+						code: s.toString(),
+						map: s.generateMap({ hires: true })
+					};
+				}
+			}
+		]
+	},
+	test(code, map) {
+		const smc = new SourceMapConsumer(map);
+		testFoo(code, smc);
+		testMain(code, smc);
+	}
+};
+
+function testFoo(code, smc) {
+	const generatedLoc = getLocation(code, code.indexOf(42));
+	const originalLoc = smc.originalPositionFor(generatedLoc);
+
+	assert.ok(/foo/.test(originalLoc.source));
+	assert.equal(originalLoc.line, 1);
+	assert.equal(originalLoc.column, 25);
+}
+
+function testMain(code, smc) {
+	const generatedLoc = getLocation(code, code.indexOf('info'));
+	const originalLoc = smc.originalPositionFor(generatedLoc);
+
+	assert.ok(/main/.test(originalLoc.source));
+	assert.equal(originalLoc.line, 3);
+	assert.equal(originalLoc.column, 8);
+}

test/sourcemaps/samples/combined-sourcemap-with-loader/foo.js

@@ -0,0 +1 @@
+export const foo = () => 42;

test/sourcemaps/samples/combined-sourcemap-with-loader/main.js

@@ -0,0 +1,3 @@
+import { foo } from './foo';
+
+console.info( `the answer is ${foo()}` );