Merge pull request #450 from davidungar/check-write-against-read

[Incremental] Add code to compare ModuleDepGraphs, & strengthen testRoundTripFixtures with it

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/DictionaryOfDictionaries.swift

@@ -138,4 +138,4 @@ extension DictionaryOfDictionaries {
 
 // MARK: - identity
 
- extension DictionaryOfDictionaries: Equatable where Value: Equatable {}
+ extension DictionaryOfDictionaries: Equatable where Value: Equatable {}

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -914,3 +914,35 @@ extension Diagnostic.Message {
   }
 }
 
+// MARK: - Checking Serialization
+
+extension ModuleDependencyGraph {
+  func matches(_ other: ModuleDependencyGraph) -> Bool {
+    guard nodeFinder.matches(other.nodeFinder),
+      tracedNodes.matches(other.tracedNodes),
+      sourceSwiftDepsMap.matches(other.sourceSwiftDepsMap),
+      externalDependencies.matches(other.externalDependencies)
+    else {
+      return false
+    }
+    return true
+  }
+}
+
+extension Set where Element == ModuleDependencyGraph.Node {
+  fileprivate func matches(_ other: Self) -> Bool {
+    self == other
+  }
+}
+
+extension BidirectionalMap where T1 == TypedVirtualPath, T2 == ModuleDependencyGraph.SwiftDeps {
+  fileprivate func matches(_ other: Self) -> Bool {
+    self == other
+  }
+}
+
+extension Set where Element == ExternalDependency {
+  fileprivate func matches(_ other: Self) -> Bool {
+    self == other
+  }
+}

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraphParts/NodeFinder.swift

@@ -248,3 +248,10 @@ fileprivate extension ModuleDependencyGraph.DependencySource {
     file.name
   }
 }
+
+// MARK: - Checking Serialization
+extension ModuleDependencyGraph.NodeFinder {
+  func matches(_ other: Self) -> Bool {
+    nodeMap == other.nodeMap && usesByDef == other.usesByDef
+  }
+}