feat(espower-source): backport espowerify to support multi-stage sourcemaps

Author: twada

Diff for: index.js

@@ -7,31 +7,74 @@
  * Licensed under the MIT license.
  *   https://github.com/twada/espower-source/blob/master/MIT-LICENSE.txt
  */
+'use strict';
+
 var espower = require('espower'),
     esprima = require('esprima'),
     escodegen = require('escodegen'),
     extend = require('xtend'),
-    convert = require('convert-source-map');
+    convert = require('convert-source-map'),
+    transfer = require('multi-stage-sourcemap').transfer;
 
-function espowerSource(jsCode, filepath, options) {
-    'use strict';
+function mergeSourceMap(incomingSourceMap, outgoingSourceMap) {
+    if (typeof outgoingSourceMap === 'string' || outgoingSourceMap instanceof String) {
+        outgoingSourceMap = JSON.parse(outgoingSourceMap);
+    }
+    if (!incomingSourceMap) {
+        return outgoingSourceMap;
+    }
+    return JSON.parse(transfer({fromSourceMap: outgoingSourceMap, toSourceMap: incomingSourceMap}));
+}
 
-    var jsAst, espowerOptions, modifiedAst, escodegenOutput, code, map;
+function handleUpstreamSourceMap (jsCode, options) {
+    var inMap;
+    if (options.sourceMap) {
+        inMap = options.sourceMap;
+    } else {
+        var commented = convert.fromSource(jsCode);
+        if (commented) {
+            inMap = commented.toObject();
+            options.sourceMap = inMap;
+        }
+    }
+    return inMap;
+}
 
-    jsAst = esprima.parse(jsCode, {tolerant: true, loc: true, tokens: true, raw: true, source: filepath});
-    espowerOptions = extend(espower.defaultOptions(), options, {
-        destructive: true,
-        path: filepath
-    });
-    modifiedAst = espower(jsAst, espowerOptions);
-    escodegenOutput = escodegen.generate(modifiedAst, {
+function instrument (jsCode, filepath, options) {
+    var jsAst = esprima.parse(jsCode, {tolerant: true, loc: true, source: filepath});
+    var modifiedAst = espower(jsAst, options);
+    // keep paths absolute by not using `file` and `sourceMapRoot`
+    // paths will be resolved by mold-source-map
+    return escodegen.generate(modifiedAst, {
         sourceMap: true,
         sourceMapWithCode: true
     });
-    code = escodegenOutput.code; // Generated source code
-    map = convert.fromJSON(escodegenOutput.map.toString());
-    map.sourcemap.sourcesContent = [jsCode];
-    return code + '\n' + map.toComment() + '\n';
+}
+
+function mergeEspowerOptions (options, filepath) {
+    return extend(espower.defaultOptions(), options, {
+        destructive: true,
+        path: filepath
+    });
+}
+
+function espowerSource(jsCode, filepath, options) {
+    var espowerOptions = mergeEspowerOptions(options, filepath);
+    var inMap = handleUpstreamSourceMap(jsCode, espowerOptions);
+    var instrumented = instrument(jsCode, filepath, espowerOptions);
+    var outMap = convert.fromJSON(instrumented.map.toString());
+    if (inMap) {
+        var mergedRawMap = mergeSourceMap(inMap, outMap.toObject());
+        var reMap = convert.fromObject(mergedRawMap);
+        reMap.setProperty('sources', inMap.sources);
+        reMap.setProperty('sourcesContent', inMap.sourcesContent);
+        return instrumented.code + '\n' + reMap.toComment() + '\n';
+    } else {
+        // Keeping paths absolute. Paths will be resolved by mold-source-map.
+        outMap.setProperty('sources', [filepath]);
+        outMap.setProperty('sourcesContent', [jsCode]);
+        return instrumented.code + '\n' + outMap.toComment() + '\n';
+    }
 }
 
 module.exports = espowerSource;