feat: Convert to async API (#489)

BREAKING CHANGE: MapStore#transformCoverage is now async and returns a
the coverage data only.  The `sourceFinder` method is now async and
provided directly on the `MapStore` instance.

Author: coreyfarrell

packages/istanbul-lib-source-maps/lib/map-store.js

@@ -6,10 +6,13 @@
 
 const path = require('path');
 const fs = require('fs');
+const { promisify } = require('util');
 const debug = require('debug')('istanbuljs');
-const SMC = require('source-map').SourceMapConsumer;
+const { SourceMapConsumer } = require('source-map');
 const pathutils = require('./pathutils');
-const transformer = require('./transformer');
+const { SourceMapTransformer } = require('./transformer');
+
+const readFile = promisify(fs.readFile);
 
 /**
  * Tracks source maps for registered files
@@ -146,45 +149,41 @@ class MapStore {
         });
     }
 
+    async sourceFinder(filePath) {
+        const content = this.sourceStore.get(filePath);
+        if (content !== undefined) {
+            return content;
+        }
+
+        if (path.isAbsolute(filePath)) {
+            return await readFile(filePath, 'utf8');
+        }
+
+        return await readFile(
+            pathutils.asAbsolute(filePath, this.baseDir),
+            'utf8'
+        );
+    }
+
     /**
      * Transforms the coverage map provided into one that refers to original
      * sources when valid mappings have been registered with this store.
      * @param {CoverageMap} coverageMap - the coverage map to transform
-     * @returns {Object} an object with 2 properties. `map` for the transformed
-     * coverage map and `sourceFinder` which is a function to return the source
-     * text for a file.
+     * @returns {Promise<CoverageMap>} the transformed coverage map
      */
-    transformCoverage(coverageMap) {
-        const sourceFinder = filePath => {
-            const content = this.sourceStore.get(filePath);
-            if (content !== undefined) {
-                return content;
-            }
-
-            if (path.isAbsolute(filePath)) {
-                return fs.readFileSync(filePath, 'utf8');
-            }
-
-            return fs.readFileSync(
-                pathutils.asAbsolute(filePath, this.baseDir)
-            );
-        };
-
+    async transformCoverage(coverageMap) {
         const hasInputSourceMaps = coverageMap
             .files()
             .some(
                 file => coverageMap.fileCoverageFor(file).data.inputSourceMap
             );
 
         if (!hasInputSourceMaps && Object.keys(this.data).length === 0) {
-            return {
-                map: coverageMap,
-                sourceFinder
-            };
+            return coverageMap;
         }
 
-        const mappedCoverage = transformer
-            .create((filePath, coverage) => {
+        const transformer = new SourceMapTransformer(
+            async (filePath, coverage) => {
                 try {
                     const obj =
                         coverage.data.inputSourceMap ||
@@ -193,7 +192,7 @@ class MapStore {
                         return null;
                     }
 
-                    const smc = new SMC(obj);
+                    const smc = new SourceMapConsumer(obj);
                     smc.sources.forEach(s => {
                         const content = smc.sourceContentFor(s);
                         if (content) {
@@ -212,13 +211,10 @@ class MapStore {
 
                     return null;
                 }
-            })
-            .transform(coverageMap);
+            }
+        );
 
-        return {
-            map: mappedCoverage,
-            sourceFinder
-        };
+        return await transformer.transform(coverageMap);
     }
 
     /**

packages/istanbul-lib-source-maps/lib/transformer.js

@@ -89,7 +89,7 @@ class SourceMapTransformer {
         return changes > 0;
     }
 
-    transform(coverageMap) {
+    async transform(coverageMap) {
         const uniqueFiles = {};
         const getMappedCoverage = file => {
             const key = getUniqueKey(file);
@@ -103,29 +103,31 @@ class SourceMapTransformer {
             return uniqueFiles[key].mappedCoverage;
         };
 
-        coverageMap.files().forEach(file => {
+        for (const file of coverageMap.files()) {
             const fc = coverageMap.fileCoverageFor(file);
-            const sourceMap = this.finder(file, fc);
-            if (!sourceMap) {
+            const sourceMap = await this.finder(file, fc);
+
+            if (sourceMap) {
+                const changed = this.processFile(
+                    fc,
+                    sourceMap,
+                    getMappedCoverage
+                );
+                if (!changed) {
+                    debug(`File [${file}] ignored, nothing could be mapped`);
+                }
+            } else {
                 uniqueFiles[getUniqueKey(file)] = {
                     file,
                     mappedCoverage: fc
                 };
-                return;
             }
-
-            const changed = this.processFile(fc, sourceMap, getMappedCoverage);
-            if (!changed) {
-                debug(`File [${file}] ignored, nothing could be mapped`);
-            }
-        });
+        }
 
         return libCoverage.createCoverageMap(getOutput(uniqueFiles));
     }
 }
 
 module.exports = {
-    create(finder, opts) {
-        return new SourceMapTransformer(finder, opts);
-    }
+    SourceMapTransformer
 };

packages/istanbul-lib-source-maps/test/map-store.test.js

@@ -6,17 +6,17 @@ const libCoverage = require('istanbul-lib-coverage');
 const MapStore = require('../lib/map-store').MapStore;
 
 describe('map store', () => {
-    it('applies the inputSourceMap from the coverage object if available', () => {
+    it('applies the inputSourceMap from the coverage object if available', async () => {
         /* shint ignore:line */
         const mapStore = new MapStore({});
 
         const coverageMap = libCoverage.createCoverageMap(coverageData);
 
-        const transformed = mapStore.transformCoverage(coverageMap);
-        assert.isUndefined(transformed.map.data.constructor);
+        const transformed = await mapStore.transformCoverage(coverageMap);
+        assert.isUndefined(transformed.data.constructor);
 
         const transformedCoverage =
-            transformed.map.data[path.resolve('./test.ts')].data;
+            transformed.data[path.resolve('./test.ts')].data;
 
         assert.deepEqual(transformedCoverage.statementMap, {
             '0': {

packages/istanbul-lib-source-maps/test/transformer.test.js

@@ -3,8 +3,8 @@
 const path = require('path');
 const assert = require('chai').assert;
 const createMap = require('istanbul-lib-coverage').createCoverageMap;
-const SMC = require('source-map').SourceMapConsumer;
-const createTransformer = require('../lib/transformer').create;
+const { SourceMapConsumer } = require('source-map');
+const { SourceMapTransformer } = require('../lib/transformer');
 
 const coverageData = {
     statementMap: {
@@ -51,13 +51,14 @@ const testDataBackslash = {
 };
 
 describe('transformer', () => {
-    it('maps statement locations', () => {
+    it('maps statement locations', async () => {
         const coverageMap = createMap({});
         coverageMap.addFileCoverage(testDataSlash.coverageData);
 
-        const mapped = createTransformer(
-            () => new SMC(testDataSlash.sourceMap)
-        ).transform(coverageMap);
+        const transformer = new SourceMapTransformer(
+            () => new SourceMapConsumer(testDataSlash.sourceMap)
+        );
+        const mapped = await transformer.transform(coverageMap);
 
         assert.deepEqual(
             mapped.data[testDataSlash.coverageData.path].statementMap,
@@ -74,17 +75,18 @@ describe('transformer', () => {
         );
     });
 
-    it('maps each file only once, /path/to/file.js and \\path\\to\\file.js are the same file', () => {
+    it('maps each file only once, /path/to/file.js and \\path\\to\\file.js are the same file', async () => {
         const coverageMap = createMap({});
 
         coverageMap.addFileCoverage(testDataSlash.coverageData);
         coverageMap.addFileCoverage(testDataBackslash.coverageData);
 
-        const mapped = createTransformer(file =>
+        const transformer = new SourceMapTransformer(file =>
             file === testDataSlash.coverageData.path
-                ? new SMC(testDataSlash.sourceMap)
+                ? new SourceMapConsumer(testDataSlash.sourceMap)
                 : undefined
-        ).transform(coverageMap);
+        );
+        const mapped = await transformer.transform(coverageMap);
 
         assert.equal(Object.keys(mapped.data).length, 1);
         assert.isDefined(mapped.data[testDataBackslash.coverageData.path]);