Allow dart2dart to output one file per library.

sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
   final Node ast;
   final TreeElements treeElements;
 
   ElementAst(AstElement element)
       : this.internal(element.resolvedAst.node, element.resolvedAst.elements);
 
   ElementAst.internal(this.ast, this.treeElements);
 }
 
 class DartBackend extends Backend {
   final List<CompilerTask> tasks;
   final bool forceStripTypes;
   final bool stripAsserts;
   // TODO(antonm): make available from command-line options.
   final bool outputAst = false;
   final Map<ClassNode, List<Node>> memberNodes;
 
+  // Should the output go to one file per input library, or everything in one
+  // file.

[Johnni Winther, 2014/08/15 08:07:31]

Paraphrase to something like "If `true`, libraries are generated into separate
files." 

[sigurdm, 2014/08/15 13:31:42]

Done.

+  final bool multiFile;
+
   PlaceholderRenamer placeholderRenamer;
 
   // TODO(zarah) Maybe change this to a command-line option.
   // Right now, it is set by the tests.
   bool useMirrorHelperLibrary = false;
 
   /// Initialized if the useMirrorHelperLibrary field is set.
   MirrorRenamer mirrorRenamer;
 
   /// Initialized when dart:mirrors is loaded if the useMirrorHelperLibrary
@@ skipping 57 matching lines @@
         ClassElement element = type.element;
         // Check all supertypes.
         if (element.allSupertypes != null) {
           element.allSupertypes.forEach(workQueue.add);
         }
       }
     }
     return true;
   }
 
-  DartBackend(Compiler compiler, List<String> strips)
+  DartBackend(Compiler compiler, List<String> strips, {this.multiFile})
       : tasks = <CompilerTask>[],
         memberNodes = new Map<ClassNode, List<Node>>(),
         forceStripTypes = strips.indexOf('types') != -1,
         stripAsserts = strips.indexOf('asserts') != -1,
         constantCompilerTask  = new DartConstantTask(compiler),
         super(compiler) {
     resolutionCallbacks = new DartResolutionCallbacks(this);
   }
 
   bool classNeedsRti(ClassElement cls) => false;
@@ skipping 141 matching lines @@
         compiler.tracer.traceGraph('Unshadow parameters', definition);
 
         TreeElementMapping treeElements = new TreeElementMapping(element);
         backend_ast.Node backendAst =
             backend_ast_emitter.emit(definition);
         Node frontend_ast = backend2frontend.emit(treeElements, backendAst);
         return new ElementAst.internal(frontend_ast, treeElements);
       }
     }
 
+    List<LibraryElement> userLibraries =
+        compiler.libraryLoader.libraries.where(isUserLibrary).toList();
+
     Set<Element> topLevelElements = new Set<Element>();
     Map<ClassElement, Set<Element>> classMembers =
         new Map<ClassElement, Set<Element>>();
 
     // Build all top level elements to emit and necessary class members.
     var newTypedefElementCallback, newClassElementCallback;
 
     void processElement(Element element, ElementAst elementAst) {
       ReferencedElementCollector collector =
           new ReferencedElementCollector(compiler,
@@ skipping 167 matching lines @@
         }
         memberNodes[elementAsts[element].ast] = members;
       }
     }
 
     if (useMirrorHelperLibrary) {
       mirrorRenamer.addRenames(placeholderRenamer.renames,
                                topLevelNodes, collector);
     }
 
-    final unparser = new EmitterUnparser(placeholderRenamer.renames,
-                                         stripTypes: forceStripTypes,
-                                         minify: compiler.enableMinification);
-    for(LibraryElement library in placeholderRenamer.platformImports) {
-      if (library.isPlatformLibrary && !library.isInternalLibrary) {
-        unparser.unparseImportTag(library.canonicalUri.toString());
+    Map<LibraryElement, String> outputUris = new Map<LibraryElement, String>();
+    Map<LibraryElement, EmitterUnparser> unparsers =
+        new Map<LibraryElement, EmitterUnparser>();
+
+    // The single unparser used if we collect all the output in one file
+    EmitterUnparser mainUnparser = multiFile
+        ? null
+        : new EmitterUnparser(placeholderRenamer.renames,
+            stripTypes: forceStripTypes,
+            minify: compiler.enableMinification);
+
+    if (multiFile) {
+      Set<String> usedLibraryNames = new Set<String>();
+      for (LibraryElement library in userLibraries) {
+        List<String> names = library.canonicalUri.pathSegments.last.split(".");
+        if (names.last == "dart") {
+          names = names.sublist(0, names.length - 1);

[floitsch, 2014/08/15 11:59:36]

names is only used when the library is not the mainApp.
It looks like a
if (library == compiler.mainApp) {
...
} else {
...
}

would simplify the code.

[sigurdm, 2014/08/15 13:31:42]

Done.

+        }
+        String mainName = compiler.outputUri.path.split('/').last;

[jgruber1, 2014/08/15 06:20:53]

Does this work on windows?

[Johnni Winther, 2014/08/15 08:07:31]

Use [Uri.pathSegments] instead of `path.split('/')`.

[floitsch, 2014/08/15 11:59:36]

You should be able to compute the mainName/mmainBaseName outside the loop.

[sigurdm, 2014/08/15 13:31:42]

I think so - Uri's should normalize path segment seperators.

[sigurdm, 2014/08/15 13:31:42]

Thanks

[sigurdm, 2014/08/15 13:31:42]

Done.

+        String mainBaseName = mainName.endsWith(".dart")
+            ? mainName.substring(0, mainName.length - 5)
+            : mainName;
+        String uri = library == compiler.mainApp
+            ? mainBaseName
+            : "$mainBaseName.${makeUnique(names.join("."), usedLibraryNames)}";

[floitsch, 2014/08/15 11:59:36]

usedLibraryNames does not contain the "mainBaseName".

[sigurdm, 2014/08/15 13:31:42]

But this is only a suffix.
So we generate
mainBaseName.$a
where $a should make the whole thing unique. It can never clash with
mainBaseName

+        outputUris[library] = uri;
+        unparsers[library] = new EmitterUnparser(placeholderRenamer.renames,
+            stripTypes: forceStripTypes, minify: compiler.enableMinification);
+      }
+
+      for(LibraryElement outputLibrary in userLibraries) {

[jgruber1, 2014/08/15 06:20:53]

Can we merge this into the previous for loop? 

[Johnni Winther, 2014/08/15 08:07:31]

No. This loop requires [outputUris] to be fully computed.

[sigurdm, 2014/08/15 13:31:42]

Acknowledged.

[sigurdm, 2014/08/15 13:31:42]

We want to set up all the ouputUris before using them for emitting the imports.

But I think setting up the unparsers can be moved down

+        EmitterUnparser unparser = unparsers[outputLibrary];
+        for (LibraryTag tag in outputLibrary.tags) {
+          if (tag is! LibraryDependency) continue;
+          LibraryDependency dependency = tag;
+          LibraryElement libraryElement =
+              outputLibrary.getLibraryFromTag(dependency);
+          String uri = outputUris.containsKey(libraryElement)
+              ? outputUris[libraryElement] + ".dart"

[Johnni Winther, 2014/08/15 08:07:31]

Use '${outputUri[LibraryElement]}.dart' instead of +

[sigurdm, 2014/08/15 13:31:42]

Done.

+              : libraryElement.canonicalUri.toString();
+          if (dependency is Import) {
+            unparser.unparseImportTag('$uri');

[jgruber1, 2014/08/15 06:20:53]

unparseImportTag(uri)?

[sigurdm, 2014/08/15 13:31:42]

Done.

+          } else {
+            unparser.unparseExportTag('$uri');
+          }
+        }
+      }
+    } else {
+      for(LibraryElement library in placeholderRenamer.platformImports) {
+        if (library.isPlatformLibrary && !library.isInternalLibrary) {
+          mainUnparser.unparseImportTag(library.canonicalUri.toString());
+        }
       }
     }
+
     for (int i = 0; i < sortedTopLevels.length; i++) {
       Element element = sortedTopLevels[i];
       Node node = topLevelNodes[i];
+      Unparser unparser = multiFile ? unparsers[element.library] : mainUnparser;
       if (node is ClassNode) {
         // TODO(smok): Filter out default constructors here.
         unparser.unparseClassWithBody(node, memberNodes[node]);
       } else {
         unparser.unparse(node);
       }
       unparser.newline();
     }
 
-    compiler.assembledCode = unparser.result;
-    compiler.outputProvider("", "dart")
-         ..add(compiler.assembledCode)
-         ..close();
-    // Output verbose info about size ratio of resulting bundle to all
-    // referenced non-platform sources.
-    logResultBundleSizeInfo(topLevelElements);
+    if (multiFile) {
+      for(LibraryElement outputLibrary in userLibraries) {
+        compiler.outputProvider(outputUris[outputLibrary], "dart")
+             ..add(unparsers[outputLibrary].result)

[Johnni Winther, 2014/08/15 08:07:31]

Add a TODO to enable direct output, i.e. avoid caching in `.result`.

[sigurdm, 2014/08/15 13:31:42]

Done.

+             ..close();
+      }
+      // TODO(sigurdm): What to do here? Probably we should get rid of
+      // compiler.assembledCode
+      compiler.assembledCode = "";
+    } else {
+      compiler.assembledCode = mainUnparser.result;
+      compiler.outputProvider("", "dart")
+           ..add(compiler.assembledCode)
+           ..close();
+
+      // Output verbose info about size ratio of resulting bundle to all
+      // referenced non-platform sources.
+      logResultBundleSizeInfo(topLevelElements);
+    }
   }
 
   void logResultBundleSizeInfo(Set<Element> topLevelElements) {
     Iterable<LibraryElement> referencedLibraries =
         compiler.libraryLoader.libraries.where(isUserLibrary);
     // Sum total size of scripts in each referenced library.
     int nonPlatformSize = 0;
     for (LibraryElement lib in referencedLibraries) {
       for (CompilationUnitElement compilationUnit in lib.compilationUnits) {
         nonPlatformSize += compilationUnit.script.file.length;
@@ skipping 201 matching lines @@
   }
 
   Constant compileMetadata(MetadataAnnotation metadata,
                            Node node,
                            TreeElements elements) {
     return measure(() {
       return constantCompiler.compileMetadata(metadata, node, elements);
     });
   }
 }