Merge pull request swiftlang#17 from nathawes/r44877860-hold-on-to-omitted-syntax-nodes-across-multiple-incremental-updates

SyntaxTreeDeserializer: Hold on to omitted nodes across multiple updates

Author: Nathan Hawes

Sources/SwiftSyntax/RawSyntax.swift

@@ -124,13 +124,6 @@ final class RawSyntax {
       }
     }).value
   }
-    
-  /// Creates a copy of `other`.
-  init(_ other: RawSyntax) {
-    self.data = other.data
-    self.presence = other.presence
-    self.id = other.id
-  }
 
   init(kind: SyntaxKind, layout: [RawSyntax?], presence: SourcePresence,
        id: SyntaxNodeId? = nil) {
@@ -341,7 +334,17 @@ extension RawSyntax {
   }
 }
 
-extension RawSyntax: Codable {
+// This is needed purely to have a self assignment initializer for
+// RawSyntax.init(from:Decoder) so we can reuse omitted nodes, instead of
+// copying them.
+private protocol _RawSyntaxFactory {}
+extension _RawSyntaxFactory {
+  init(_instance: Self) {
+    self = _instance
+  }
+}
+
+extension RawSyntax: Codable, _RawSyntaxFactory {
   /// Creates a RawSyntax from the provided Foundation Decoder.
   convenience init(from decoder: Decoder) throws {
     let container = try decoder.container(keyedBy: CodingKeys.self)
@@ -359,7 +362,7 @@ extension RawSyntax: Codable {
       guard let lookupNode = lookupFunc(id) else {
         throw IncrementalDecodingError.nodeLookupFailed(id)
       }
-      self.init(lookupNode)
+      self.init(_instance: lookupNode)
       return
     }
 

Sources/SwiftSyntax/WeakLookupTable.swift

@@ -188,7 +188,9 @@ class WeakLookupTable<Element: Identifiable & AnyObject> {
     return reserveCapacity(estimatedCount &+ 1)
   }
 
-  /// Inserts the given object into the table.
+  /// Inserts the given object into the table if the table doesn't already
+  /// contain an object with the same identifier.
+  /// - returns: true if the object was inserted
   @discardableResult
   func insert(_ obj: Element) -> Bool {
     var (pos, alreadyExists) = _findHole(obj.id)

Tests/SwiftSyntaxTest/DeserializeFile.swift

@@ -15,4 +15,18 @@ public class DecodeSyntaxTestCase: XCTestCase {
       XCTAssertEqual("\(parsed)", source)
     }())
   }
+
+  public func testIncrementalDeserialize() {
+    XCTAssertNoThrow(try {
+      let deserializer = SyntaxTreeDeserializer()
+      var tree: SourceFileSyntax? = nil
+      let responses = try (1...3).map {
+        try Data(contentsOf: getInput("incremental-deserialize-\($0).json"))
+      }
+      for data in responses {
+        tree = try deserializer.deserialize(data, serializationFormat: .json)
+      }
+      XCTAssertEqual(tree?.description, "x\ny")
+    }())
+  }
 }

Tests/SwiftSyntaxTest/Inputs/incremental-deserialize-1.json

@@ -0,0 +1,51 @@
+{
+  "id":39,
+  "kind":"SourceFile",
+  "layout":[
+    {
+      "id":38,
+      "kind":"CodeBlockItemList",
+      "layout":[
+        {
+          "id":35,
+          "kind":"CodeBlockItem",
+          "layout":[
+            {
+              "id":34,
+              "kind":"IdentifierExpr",
+              "layout":[
+                {
+                  "id":33,
+                  "tokenKind":{
+                    "kind":"identifier",
+                    "text":"x"
+                  },
+                  "leadingTrivia":[],
+                  "trailingTrivia":[],
+                  "presence":"Present"
+                },
+                null
+              ],
+              "presence":"Present"
+            },
+            null,
+            null
+          ],
+          "presence":"Present"
+        }
+      ],
+      "presence":"Present"
+    },
+    {
+      "id":37,
+      "tokenKind":{
+        "kind":"eof",
+        "text":""
+      },
+      "leadingTrivia":[],
+      "trailingTrivia":[],
+      "presence":"Present"
+    }
+  ],
+  "presence":"Present"
+}

Tests/SwiftSyntaxTest/Inputs/incremental-deserialize-2.json

@@ -0,0 +1,33 @@
+{
+  "id":45,
+  "kind":"SourceFile",
+  "layout":[
+    {
+      "id":44,
+      "kind":"CodeBlockItemList",
+      "layout":[
+        {
+          "id":35,
+          "omitted":true
+        }
+      ],
+      "presence":"Present"
+    },
+    {
+      "id":43,
+      "tokenKind":{
+        "kind":"eof",
+        "text":""
+      },
+      "leadingTrivia":[
+        {
+          "kind":"Newline",
+          "value":1
+        }
+      ],
+      "trailingTrivia":[],
+      "presence":"Present"
+    }
+  ],
+  "presence":"Present"
+}

Tests/SwiftSyntaxTest/Inputs/incremental-deserialize-3.json

@@ -0,0 +1,60 @@
+{
+  "id":54,
+  "kind":"SourceFile",
+  "layout":[
+    {
+      "id":53,
+      "kind":"CodeBlockItemList",
+      "layout":[
+        {
+          "id":35,
+          "omitted":true
+        },
+        {
+          "id":50,
+          "kind":"CodeBlockItem",
+          "layout":[
+            {
+              "id":49,
+              "kind":"IdentifierExpr",
+              "layout":[
+                {
+                  "id":48,
+                  "tokenKind":{
+                    "kind":"identifier",
+                    "text":"y"
+                  },
+                  "leadingTrivia":[
+                    {
+                      "kind":"Newline",
+                      "value":1
+                    }
+                  ],
+                  "trailingTrivia":[],
+                  "presence":"Present"
+                },
+                null
+              ],
+              "presence":"Present"
+            },
+            null,
+            null
+          ],
+          "presence":"Present"
+        }
+      ],
+      "presence":"Present"
+    },
+    {
+      "id":52,
+      "tokenKind":{
+        "kind":"eof",
+        "text":""
+      },
+      "leadingTrivia":[],
+      "trailingTrivia":[],
+      "presence":"Present"
+    }
+  ],
+  "presence":"Present"
+}

Tests/SwiftSyntaxTest/WeakLookupTableTest.swift

@@ -108,6 +108,18 @@ public class WeakLookupTableTestCase: XCTestCase {
 
     _ = tree // Prevents 'never read' warning
   }
+
+  func testSameIdentifierDifferentObject() {
+    let table = WeakLookupTable<MinimalNode>()
+
+    let object1 = MinimalNode(id: "1", children: [])
+    let object2 = MinimalNode(id: "1", children: [])
+
+    XCTAssertTrue(table.insert(object1))
+    XCTAssert(table["1"] === object1)
+    XCTAssertFalse(table.insert(object2))
+    XCTAssert(table["1"] === object1)
+  }
 }
 
 #endif // DEBUG