Deduplicate module sources in cache

Author: CompuIves

packages/app/src/sandbox/eval/transpiled-module.js

@@ -32,18 +32,26 @@ class ModuleSource {
   fileName: string;
   compiledCode: string;
   sourceMap: ?SourceMap;
+  sourceEqualsCompiled: boolean;
 
-  constructor(fileName: string, compiledCode: string, sourceMap: ?SourceMap) {
+  constructor(
+    fileName: string,
+    compiledCode: string,
+    sourceMap: ?SourceMap,
+    sourceEqualsCompiled = false
+  ) {
     this.fileName = fileName;
     this.compiledCode = compiledCode;
     this.sourceMap = sourceMap;
+    this.sourceEqualsCompiled = sourceEqualsCompiled;
   }
 }
 
 export type SerializedTranspiledModule = {
   module: Module,
   query: string,
   source: ?ModuleSource,
+  sourceEqualsCompiled: boolean,
   assets: {
     [name: string]: ModuleSource,
   },
@@ -594,13 +602,21 @@ export default class TranspiledModule {
       }
     }
 
-    // Add the source of the file by default, this is important for source mapping
-    // errors back to their origin
-    code = `${code}\n//# sourceURL=${location.origin}${this.module.path}${
+    const sourceEqualsCompiled = code === this.module.code;
+    const sourceURL = `//# sourceURL=${location.origin}${this.module.path}${
       this.query ? `?${this.hash}` : ''
     }`;
 
-    this.source = new ModuleSource(this.module.path, code, finalSourceMap);
+    // Add the source of the file by default, this is important for source mapping
+    // errors back to their origin
+    code = `${code}\n${sourceURL}`;
+
+    this.source = new ModuleSource(
+      this.module.path,
+      code,
+      finalSourceMap,
+      sourceEqualsCompiled
+    );
 
     if (
       this.previousSource &&
@@ -902,13 +918,19 @@ export default class TranspiledModule {
   serialize(): SerializedTranspiledModule {
     const serializableObject = {};
 
+    const sourceEqualsCompiled =
+      this.source && this.source.sourceEqualsCompiled;
+
     serializableObject.query = this.query;
     serializableObject.assets = this.assets;
     serializableObject.module = this.module;
     serializableObject.emittedAssets = this.emittedAssets;
     serializableObject.isEntry = this.isEntry;
     serializableObject.isTestFile = this.isTestFile;
-    serializableObject.source = this.source;
+    if (!sourceEqualsCompiled) {
+      serializableObject.source = this.source;
+    }
+    serializableObject.sourceEqualsCompiled = sourceEqualsCompiled;
     serializableObject.childModules = this.childModules.map(m => m.getId());
     serializableObject.dependencies = Array.from(this.dependencies).map(m =>
       m.getId()
@@ -946,7 +968,17 @@ export default class TranspiledModule {
     this.emittedAssets = data.emittedAssets;
     this.isEntry = data.isEntry;
     this.isTestFile = data.isTestFile;
-    this.source = data.source;
+
+    if (data.sourceEqualsCompiled) {
+      this.source = new ModuleSource(
+        this.module.path,
+        this.module.code,
+        null,
+        true
+      );
+    } else {
+      this.source = data.source;
+    }
 
     const loadModule = (
       depId: string,