Linter Demo

Errors: 1

Warnings: 22

File: /home/fstrocco/Dart/dart/benchmark/compiler/lib/src/deferred_load.dart

// Copyright (c) 2014, 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. library deferred_load; import 'constants/expressions.dart'; import 'constants/values.dart' show ConstantValue, ConstructedConstantValue, DeferredConstantValue, StringConstantValue; import 'dart2jslib.dart' show Backend, Compiler, CompilerTask, invariant, MessageKind; import 'dart_backend/dart_backend.dart' show DartBackend; import 'js_backend/js_backend.dart' show JavaScriptBackend; import 'elements/elements.dart' show AstElement, ClassElement, Element, ElementKind, Elements, FunctionElement, LibraryElement, MetadataAnnotation, PrefixElement, ScopeContainerElement, TypedefElement, VoidElement; import 'util/util.dart' show Link, makeUnique; import 'util/uri_extras.dart' as uri_extras; import 'util/setlet.dart' show Setlet; import 'tree/tree.dart' show Import, LibraryTag, LibraryDependency, LiteralDartString, LiteralString, NewExpression, Node; import 'tree/tree.dart' as ast; import 'resolution/resolution.dart' show AnalyzableElementX, TreeElements; /// A "hunk" of the program that will be loaded whenever one of its [imports] /// are loaded. /// /// Elements that are only used in one deferred import, is in an OutputUnit with /// the deferred import as single element in the [imports] set. /// /// Whenever a deferred Element is shared between several deferred imports it is /// in an output unit with those imports in the [imports] Set. /// /// OutputUnits are equal if their [imports] are equal. class OutputUnit { /// The deferred imports that will load this output unit when one of them is /// loaded. final Setlet<Import> imports = new Setlet<Import>(); /// `true` if this output unit is for the main output file. final bool isMainOutput; /// A unique name representing this [OutputUnit]. /// Based on the set of [imports]. String name; OutputUnit({this.isMainOutput: false}); String toString() => "OutputUnit($name)"; bool operator==(OutputUnit other) { return imports.length == other.imports.length && imports.containsAll(other.imports); } int get hashCode { int sum = 0; for (Import import in imports) { sum = (sum + import.hashCode) & 0x3FFFFFFF; // Stay in 30 bit range. } return sum; } } /// For each deferred import, find elements and constants to be loaded when that /// import is loaded. Elements that are used by several deferred imports are in /// shared OutputUnits. class DeferredLoadTask extends CompilerTask { /// The name of this task. String get name => 'Deferred Loading'; /// DeferredLibrary from dart:async ClassElement get deferredLibraryClass => compiler.deferredLibraryClass; /// A synthetic [Import] representing the loading of the main /// program. final Import _fakeMainImport = new Import(null, new LiteralString(null, new LiteralDartString("main")), null, null, null); /// The OutputUnit that will be loaded when the program starts. final OutputUnit mainOutputUnit = new OutputUnit(isMainOutput: true); /// A set containing (eventually) all output units that will result from the /// program. final Set<OutputUnit> allOutputUnits = new Set<OutputUnit>(); /// Will be `true` if the program contains deferred libraries. bool isProgramSplit = false; /// A mapping from the name of a defer import to all the output units it /// depends on in a list of lists to be loaded in the order they appear. /// /// For example {"lib1": [[lib1_lib2_lib3], [lib1_lib2, lib1_lib3], /// [lib1]]} would mean that in order to load "lib1" first the hunk /// lib1_lib2_lib2 should be loaded, then the hunks lib1_lib2 and lib1_lib3 /// can be loaded in parallel. And finally lib1 can be loaded. final Map<String, List<OutputUnit>> hunksToLoad = new Map<String, List<OutputUnit>>(); final Map<Import, String> importDeferName = new Map<Import, String>(); /// A mapping from elements and constants to their output unit. Query this via /// [outputUnitForElement] final Map<Element, OutputUnit> _elementToOutputUnit = new Map<Element, OutputUnit>(); /// A mapping from constants to their output unit. Query this via /// [outputUnitForConstant] final Map<ConstantValue, OutputUnit> _constantToOutputUnit = new Map<ConstantValue, OutputUnit>(); /// All the imports with a [DeferredLibrary] annotation, mapped to the /// [LibraryElement] they import. /// The main library is included in this set for convenience. final Map<Import, LibraryElement> _allDeferredImports = new Map<Import, LibraryElement>(); /// Because the token-stream is forgotten later in the program, we cache a /// description of each deferred import. final _deferredImportDescriptions = new Map<Import, ImportDescription>(); // For each deferred import we want to know exactly what elements have to // be loaded. Map<Import, Set<Element>> _importedDeferredBy = null; Map<Import, Set<ConstantValue>> _constantsDeferredBy = null; Set<Element> _mainElements = new Set<Element>(); DeferredLoadTask(Compiler compiler) : super(compiler) { mainOutputUnit.imports.add(_fakeMainImport); } Backend get backend => compiler.backend; /// Returns the [OutputUnit] where [element] belongs. OutputUnit outputUnitForElement(Element element) { if (!isProgramSplit) return mainOutputUnit; element = element.implementation; while (!_elementToOutputUnit.containsKey(element)) { // TODO(21051): workaround: it looks like we output annotation constants // for classes that we don't include in the output. This seems to happen // when we have reflection but can see that some classes are not needed. // We still add the annotation but don't run through it below (where we // assign every element to its output unit). if (element.enclosingElement == null) { _elementToOutputUnit[element] = mainOutputUnit; break; } element = element.enclosingElement.implementation; } return _elementToOutputUnit[element]; } /// Returns the [OutputUnit] where [constant] belongs. OutputUnit outputUnitForConstant(ConstantValue constant) { if (!isProgramSplit) return mainOutputUnit; return _constantToOutputUnit[constant]; } bool isDeferred(Element element) { return outputUnitForElement(element) != mainOutputUnit; } /// Returns true if e1 and e2 are in the same output unit. bool inSameOutputUnit(Element e1, Element e2) { return outputUnitForElement(e1) == outputUnitForElement(e2); } void registerConstantDeferredUse(DeferredConstantValue constant, PrefixElement prefix) { OutputUnit outputUnit = new OutputUnit(); outputUnit.imports.add(prefix.deferredImport); _constantToOutputUnit[constant] = outputUnit; } /// Answers whether [element] is explicitly deferred when referred to from /// [library]. bool _isExplicitlyDeferred(Element element, LibraryElement library) { Link<Import> imports = _getImports(element, library); // If the element is not imported explicitly, it is implicitly imported // not deferred. if (imports.isEmpty) return false; // An element could potentially be loaded by several imports. If all of them // is explicitly deferred, we say the element is explicitly deferred. // TODO(sigurdm): We might want to give a warning if the imports do not // agree. return imports.every((Import import) => import.isDeferred); } /// Returns a [Link] of every [Import] that imports [element] into [library]. Link<Import> _getImports(Element element, LibraryElement library) { if (element.isClassMember) { element = element.enclosingClass; } if (element.isAccessor) { element = (element as FunctionElement).abstractField; } return library.getImportsFor(element); } /// Finds all elements and constants that [element] depends directly on. /// (not the transitive closure.) /// /// Adds the results to [elements] and [constants]. void _collectAllElementsAndConstantsResolvedFrom( Element element, Set<Element> elements, Set<ConstantValue> constants, isMirrorUsage) { /// Recursively add the constant and its dependencies to [constants]. void addConstants(ConstantValue constant) { if (constants.contains(constant)) return; constants.add(constant); if (constant is ConstructedConstantValue) { elements.add(constant.type.element); } constant.getDependencies().forEach(addConstants); } /// Collects all direct dependencies of [element]. /// /// The collected dependent elements and constants are are added to /// [elements] and [constants] respectively. void collectDependencies(Element element) { // TODO(johnniwinther): Remove this when [AbstractFieldElement] has been // removed. if (element is! AstElement) return; AstElement astElement = element; // TODO(sigurdm): We want to be more specific about this - need a better // way to query "liveness". if (astElement is! TypedefElement && !compiler.enqueuer.resolution.hasBeenResolved(astElement)) { return; } TreeElements treeElements = astElement.resolvedAst.elements; assert(treeElements != null); for (Element dependency in treeElements.allElements) { if (dependency.isLocal && !dependency.isFunction) continue; if (dependency.isErroneous) continue; if (dependency.isTypeVariable) continue; elements.add(dependency); } treeElements.forEachConstantNode((Node node, _) { // Explicitly depend on the backend constants. addConstants( backend.constants.getConstantForNode(node, treeElements).value); }); elements.addAll(treeElements.otherDependencies); } // TODO(sigurdm): How is metadata on a patch-class handled? for (MetadataAnnotation metadata in element.metadata) { ConstantExpression constant = backend.constants.getConstantForMetadata(metadata); if (constant != null) { addConstants(constant.value); } } if (element.isClass) { // If we see a class, add everything its live instance members refer // to. Static members are not relevant, unless we are processing // extra dependencies due to mirrors. void addLiveInstanceMember(Element element) { if (!compiler.enqueuer.resolution.hasBeenResolved(element)) return; if (!isMirrorUsage && !element.isInstanceMember) return; collectDependencies(element.implementation); } ClassElement cls = element.declaration; cls.forEachLocalMember(addLiveInstanceMember); if (cls.implementation != cls) { // TODO(ahe): Why doesn't ClassElement.forEachLocalMember do this? cls.implementation.forEachLocalMember(addLiveInstanceMember); } for (var type in cls.implementation.allSupertypes) { elements.add(type.element.implementation); } elements.add(cls.implementation); } else if (Elements.isStaticOrTopLevel(element) || element.isConstructor) { collectDependencies(element); } if (element.isGenerativeConstructor) { // When instantiating a class, we record a reference to the // constructor, not the class itself. We must add all the // instance members of the constructor's class. ClassElement implementation = element.enclosingClass.implementation; _collectAllElementsAndConstantsResolvedFrom( implementation, elements, constants, isMirrorUsage); } // Other elements, in particular instance members, are ignored as // they are processed as part of the class. } /// Returns the transitive closure of all libraries that are imported /// from root without DeferredLibrary annotations. Set<LibraryElement> _nonDeferredReachableLibraries(LibraryElement root) { Set<LibraryElement> result = new Set<LibraryElement>(); void traverseLibrary(LibraryElement library) { if (result.contains(library)) return; result.add(library); iterateTags(LibraryElement library) { // TODO(sigurdm): Make helper getLibraryDependencyTags when tags is // changed to be a List instead of a Link. for (LibraryTag tag in library.tags) { if (tag is! LibraryDependency) continue; LibraryDependency libraryDependency = tag; if (!(libraryDependency is Import && libraryDependency.isDeferred)) { LibraryElement importedLibrary = library.getLibraryFromTag(tag); traverseLibrary(importedLibrary); } } } iterateTags(library); if (library.isPatched) { iterateTags(library.implementation); } } traverseLibrary(root); result.add(compiler.coreLibrary); return result; } /// Recursively traverses the graph of dependencies from [element], mapping /// deferred imports to each dependency it needs in the sets /// [_importedDeferredBy] and [_constantsDeferredBy]. void _mapDependencies(Element element, Import import, {isMirrorUsage: false}) { Set<Element> elements = _importedDeferredBy.putIfAbsent(import, () => new Set<Element>()); Set<ConstantValue> constants = _constantsDeferredBy.putIfAbsent(import, () => new Set<ConstantValue>()); // Only process elements once, unless we are doing dependencies due to // mirrors, which are added in additional traversals. if (!isMirrorUsage && elements.contains(element)) return; // Anything used directly by main will be loaded from the start // We do not need to traverse it again. if (import != _fakeMainImport && _mainElements.contains(element)) return; // Here we modify [_importedDeferredBy]. elements.add(element); Set<Element> dependentElements = new Set<Element>(); // This call can modify [_importedDeferredBy] and [_constantsDeferredBy]. _collectAllElementsAndConstantsResolvedFrom( element, dependentElements, constants, isMirrorUsage); LibraryElement library = element.library; for (Element dependency in dependentElements) { if (_isExplicitlyDeferred(dependency, library)) { for (Import deferredImport in _getImports(dependency, library)) { _mapDependencies(dependency, deferredImport); }; } else { _mapDependencies(dependency, import); } } } /// Adds extra dependencies coming from mirror usage. /// /// The elements are added with [_mapDependencies]. void _addMirrorElements() { void mapDependenciesIfResolved(Element element, Import deferredImport) { // If an element is the target of a MirrorsUsed annotation but never used // It will not be resolved, and we should not call isNeededForReflection. // TODO(sigurdm): Unresolved elements should just answer false when // asked isNeededForReflection. Instead an internal error is triggered. // So we have to filter them out here. if (element is AnalyzableElementX && !element.hasTreeElements) return; if (compiler.backend.isAccessibleByReflection(element)) { _mapDependencies(element, deferredImport, isMirrorUsage: true); } } // For each deferred import we analyze all elements reachable from the // imported library through non-deferred imports. handleLibrary(LibraryElement library, Import deferredImport) { library.implementation.forEachLocalMember((Element element) { mapDependenciesIfResolved(element, deferredImport); }); for (MetadataAnnotation metadata in library.metadata) { ConstantExpression constant = backend.constants.getConstantForMetadata(metadata); if (constant != null) { _mapDependencies(constant.value.getType(compiler.coreTypes).element, deferredImport); } } for (LibraryTag tag in library.tags) { for (MetadataAnnotation metadata in tag.metadata) { ConstantExpression constant = backend.constants.getConstantForMetadata(metadata); if (constant != null) { _mapDependencies(constant.value.getType(compiler.coreTypes).element, deferredImport); } } } } for (Import deferredImport in _allDeferredImports.keys) { LibraryElement deferredLibrary = _allDeferredImports[deferredImport]; for (LibraryElement library in _nonDeferredReachableLibraries(deferredLibrary)) { handleLibrary(library, deferredImport); } } } /// Computes a unique string for the name field for each outputUnit. /// /// Also sets up the [hunksToLoad] mapping. void _assignNamesToOutputUnits(Set<OutputUnit> allOutputUnits) { Set<String> usedImportNames = new Set<String>(); // Finds the first argument to the [DeferredLibrary] annotation void computeImportDeferName(Import import) { String result; if (import == _fakeMainImport) { result = "main"; } else if (import.isDeferred) { result = import.prefix.toString(); } else { Link<MetadataAnnotation> metadatas = import.metadata; assert(metadatas != null); for (MetadataAnnotation metadata in metadatas) { metadata.ensureResolved(compiler); Element element = metadata.constant.value.getType(compiler.coreTypes).element; if (element == deferredLibraryClass) { ConstructedConstantValue constant = metadata.constant.value; StringConstantValue s = constant.fields[0]; result = s.primitiveValue.slowToString(); break; } } } assert(result != null); importDeferName[import] = makeUnique(result, usedImportNames);; } int counter = 1; for (Import import in _allDeferredImports.keys) { computeImportDeferName(import); } for (OutputUnit outputUnit in allOutputUnits) { if (outputUnit == mainOutputUnit) { outputUnit.name = "main"; } else { outputUnit.name = "$counter"; ++counter; } } List sortedOutputUnits = new List.from(allOutputUnits); // Sort the output units in descending order of the number of imports they // include. // The loading of the output units mut be ordered because a superclass needs // to be initialized before its subclass. // But a class can only depend on another class in an output unit shared by // a strict superset of the imports: // By contradiction: Assume a class C in output unit shared by imports in // the set S1 = (lib1,.., lib_n) depends on a class D in an output unit // shared by S2 such that S2 not a superset of S1. Let lib_s be a library in // S1 not in S2. lib_s must depend on C, and then in turn on D therefore D // is not in the right output unit. sortedOutputUnits.sort((a, b) => b.imports.length - a.imports.length); // For each deferred import we find out which outputUnits to load. for (Import import in _allDeferredImports.keys) { if (import == _fakeMainImport) continue; hunksToLoad[importDeferName[import]] = new List<OutputUnit>(); for (OutputUnit outputUnit in sortedOutputUnits) { if (outputUnit == mainOutputUnit) continue; if (outputUnit.imports.contains(import)) { hunksToLoad[importDeferName[import]].add(outputUnit); } } } } void onResolutionComplete(FunctionElement main) { if (!isProgramSplit) { allOutputUnits.add(mainOutputUnit); return; } if (main == null) return; LibraryElement mainLibrary = main.library; _importedDeferredBy = new Map<Import, Set<Element>>(); _constantsDeferredBy = new Map<Import, Set<ConstantValue>>(); _importedDeferredBy[_fakeMainImport] = _mainElements; measureElement(mainLibrary, () { // Starting from main, traverse the program and find all dependencies. _mapDependencies(compiler.mainFunction, _fakeMainImport); // Also add "global" dependencies to the main OutputUnit. These are // things that the backend need but cannot associate with a particular // element, for example, startRootIsolate. This set also contains // elements for which we lack precise information. for (Element element in compiler.globalDependencies.otherDependencies) { _mapDependencies(element, _fakeMainImport); } // Now check to see if we have to add more elements due to mirrors. if (compiler.mirrorsLibrary != null) { _addMirrorElements(); } // Build the OutputUnits using these two maps. Map<Element, OutputUnit> elementToOutputUnitBuilder = new Map<Element, OutputUnit>(); Map<ConstantValue, OutputUnit> constantToOutputUnitBuilder = new Map<ConstantValue, OutputUnit>(); // Reverse the mappings. For each element record an OutputUnit collecting // all deferred imports mapped to this element. Same for constants. for (Import import in _importedDeferredBy.keys) { for (Element element in _importedDeferredBy[import]) { // Only one file should be loaded when the program starts, so make // sure that only one OutputUnit is created for [fakeMainImport]. if (import == _fakeMainImport) { elementToOutputUnitBuilder[element] = mainOutputUnit; } else { elementToOutputUnitBuilder .putIfAbsent(element, () => new OutputUnit()) .imports.add(import); } } for (ConstantValue constant in _constantsDeferredBy[import]) { // Only one file should be loaded when the program starts, so make // sure that only one OutputUnit is created for [fakeMainImport]. if (import == _fakeMainImport) { constantToOutputUnitBuilder[constant] = mainOutputUnit; } else { constantToOutputUnitBuilder .putIfAbsent(constant, () => new OutputUnit()) .imports.add(import); } } } // Release maps; _importedDeferredBy = null; _constantsDeferredBy = null; // Find all the output units elements/constants have been mapped to, and // canonicalize them. elementToOutputUnitBuilder.forEach( (Element element, OutputUnit outputUnit) { OutputUnit representative = allOutputUnits.lookup(outputUnit); if (representative == null) { representative = outputUnit; allOutputUnits.add(representative); } _elementToOutputUnit[element] = representative; }); constantToOutputUnitBuilder.forEach( (ConstantValue constant, OutputUnit outputUnit) { OutputUnit representative = allOutputUnits.lookup(outputUnit); if (representative == null) { representative = outputUnit; allOutputUnits.add(representative); } _constantToOutputUnit[constant] = representative; }); // Generate a unique name for each OutputUnit. _assignNamesToOutputUnits(allOutputUnits); }); } void beforeResolution(Compiler compiler) { if (compiler.mainApp == null) return; _allDeferredImports[_fakeMainImport] = compiler.mainApp; var lastDeferred; // When detecting duplicate prefixes of deferred libraries there are 4 // cases of duplicate prefixes: // 1. // import "lib.dart" deferred as a; // import "lib2.dart" deferred as a; // 2. // import "lib.dart" deferred as a; // import "lib2.dart" as a; // 3. // import "lib.dart" as a; // import "lib2.dart" deferred as a; // 4. // import "lib.dart" as a; // import "lib2.dart" as a; // We must be able to signal error for case 1, 2, 3, but accept case 4. // The prefixes that have been used by any imports in this library. Setlet<String> usedPrefixes = new Setlet<String>(); // The last deferred import we saw with a given prefix (if any). Map<String, Import> prefixDeferredImport = new Map<String, Import>(); for (LibraryElement library in compiler.libraryLoader.libraries) { compiler.withCurrentElement(library, () { prefixDeferredImport.clear(); usedPrefixes.clear(); // TODO(sigurdm): Make helper getLibraryImportTags when tags is a List // instead of a Link. for (LibraryTag tag in library.tags) { if (tag is! Import) continue; Import import = tag; /// Give an error if the old annotation-based syntax has been used. Link<MetadataAnnotation> metadataList = import.metadata; if (metadataList != null) { for (MetadataAnnotation metadata in metadataList) { metadata.ensureResolved(compiler); Element element = metadata.constant.value.getType(compiler.coreTypes).element; if (element == deferredLibraryClass) { compiler.reportError( import, MessageKind.DEFERRED_OLD_SYNTAX); } } } String prefix = (import.prefix != null) ? import.prefix.toString() : null; // The last import we saw with the same prefix. Import previousDeferredImport = prefixDeferredImport[prefix]; if (import.isDeferred) { LibraryElement importedLibrary = library.getLibraryFromTag(import); _allDeferredImports[import] = importedLibrary; if (prefix == null) { compiler.reportError(import, MessageKind.DEFERRED_LIBRARY_WITHOUT_PREFIX); } else { prefixDeferredImport[prefix] = import; _deferredImportDescriptions[import] = new ImportDescription(import, library, compiler); } isProgramSplit = true; lastDeferred = import; } if (prefix != null) { if (previousDeferredImport != null || (import.isDeferred && usedPrefixes.contains(prefix))) { Import failingImport = (previousDeferredImport != null) ? previousDeferredImport : import; compiler.reportError(failingImport.prefix, MessageKind.DEFERRED_LIBRARY_DUPLICATE_PREFIX); } usedPrefixes.add(prefix); } } }); } Backend backend = compiler.backend; if (isProgramSplit && backend is JavaScriptBackend) { backend.registerCheckDeferredIsLoaded(compiler.globalDependencies); } if (isProgramSplit && backend is DartBackend) { // TODO(sigurdm): Implement deferred loading for dart2dart. compiler.reportWarning( lastDeferred, MessageKind.DEFERRED_LIBRARY_DART_2_DART); isProgramSplit = false; } } /// If [send] is a static send with a deferred element, returns the /// [PrefixElement] that the first prefix of the send resolves to. /// Otherwise returns null. /// /// Precondition: send must be static. /// /// Example: /// /// import "a.dart" deferred as a; /// /// main() { /// print(a.loadLibrary.toString()); /// a.loadLibrary().then((_) { /// a.run(); /// a.foo.method(); /// }); /// } /// /// Returns null for a.loadLibrary() (the special /// function loadLibrary is not deferred). And returns the PrefixElement for /// a.run() and a.foo. /// a.loadLibrary.toString() and a.foo.method() are dynamic sends - and /// this functions should not be called on them. PrefixElement deferredPrefixElement(ast.Send send, TreeElements elements) { Element element = elements[send]; // The DeferredLoaderGetter is not deferred, therefore we do not return the // prefix. if (element != null && element.isDeferredLoaderGetter) return null; ast.Node firstNode(ast.Node node) { if (node is! ast.Send) { return node; } else { ast.Send send = node; ast.Node receiver = send.receiver; ast.Node receiverFirst = firstNode(receiver); if (receiverFirst != null) { return receiverFirst; } else { return firstNode(send.selector); } } } ast.Node first = firstNode(send); ast.Node identifier = first.asIdentifier(); if (identifier == null) return null; Element maybePrefix = elements[identifier]; if (maybePrefix != null && maybePrefix.isPrefix) { PrefixElement prefixElement = maybePrefix; if (prefixElement.isDeferred) { return prefixElement; } } return null; } /// Returns a json-style map for describing what files that are loaded by a /// given deferred import. /// The mapping is structured as: /// library uri -> {"name": library name, "files": (prefix -> list of files)} /// Where /// /// - <library uri> is the relative uri of the library making a deferred /// import /// - <library name> is the name of the libary, and "<unnamed>" if it is /// unnamed. /// - <prefix> is the `as` prefix used for a given deferred import. /// - <list of files> is a list of the filenames the must be loaded when that /// import is loaded. Map<String, Map<String, dynamic>> computeDeferredMap() { JavaScriptBackend backend = compiler.backend; Map<String, Map<String, dynamic>> mapping = new Map<String, Map<String, dynamic>>(); _deferredImportDescriptions.keys.forEach((ast.Import import) { List<OutputUnit> outputUnits = hunksToLoad[importDeferName[import]]; ImportDescription description = _deferredImportDescriptions[import]; Map<String, dynamic> libraryMap = mapping.putIfAbsent(description.importingUri, () => <String, dynamic>{"name": description.importingLibraryName, "imports": <String, List<String>>{}}); libraryMap["imports"][description.prefix] = outputUnits.map( (OutputUnit outputUnit) { return backend.deferredPartFileName(outputUnit.name); }).toList(); }); return mapping; } } class ImportDescription { /// Relative uri to the importing library. final String importingUri; /// The prefix this import is imported as. final String prefix; final LibraryElement _importingLibrary; ImportDescription(Import import, LibraryElement importingLibrary, Compiler compiler) : importingUri = uri_extras.relativize( compiler.mainApp.canonicalUri, importingLibrary.canonicalUri, false), prefix = import.prefix.source, _importingLibrary = importingLibrary; String get importingLibraryName { String libraryName = _importingLibrary.getLibraryName(); return libraryName == "" ? "<unnamed>" : libraryName; } }