Add utils for incremental parse test

Sources/_SwiftSyntaxTestSupport/IncrementalParseTestUtils.swift

@@ -0,0 +1,137 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+import SwiftParser
+import XCTest
+
+/// This function is used to verify the correctness of incremental parsing
+/// containing three parts:
+/// 1. Round-trip on the incrementally parsed syntax tree.
+/// 2. verify that incrementally parsing the edited source base on the original source produces the same syntax tree as reparsing the post-edit file from scratch.
+/// 3. verify the reused nodes fall into expectations.
+public func assertIncrementalParse(
+  _ source: String,
+  reusedNodes expectedReusedNodes: [ReusedNodeSpec] = [],
+  file: StaticString = #file,
+  line: UInt = #line
+) {
+  let (concurrentEdits, originalSource, editedSource) = getEditsAndSources(source)
+
+  let originalString = String(originalSource)
+  let editedString = String(editedSource)
+
+  let originalTree = Parser.parse(source: originalString)
+
+  let reusedNodesCollector = IncrementalParseReusedNodeCollector()
+  let transition = IncrementalParseTransition(previousTree: originalTree, edits: concurrentEdits, reusedNodeDelegate: reusedNodesCollector)
+
+  let newTree = Parser.parse(source: editedString)
+  let incrementallyParsedNewTree = Parser.parse(source: editedString, parseTransition: transition)
+
+  // Round-trip
+  assertStringsEqualWithDiff(
+    editedString,
+    "\(incrementallyParsedNewTree)",
+    additionalInfo: """
+      Source failed to round-trip when parsing incrementally
+
+      Actual syntax tree:
+      \(incrementallyParsedNewTree.debugDescription)
+      """,
+    file: file,
+    line: line
+  )
+
+  // Substructure
+  let subtreeMatcher = SubtreeMatcher(Syntax(incrementallyParsedNewTree), markers: [:])
+  do {
+    try subtreeMatcher.assertSameStructure(Syntax(newTree), includeTrivia: true, file: file, line: line)
+  } catch {
+    XCTFail("Matching for a subtree failed with error: \(error)", file: file, line: line)
+  }
+
+  // Re-used nodes
+  if reusedNodesCollector.rangeAndNodes.count != expectedReusedNodes.count {
+    XCTFail(
+      """
+      Expected \(expectedReusedNodes.count) re-used nodes but received \(reusedNodesCollector.rangeAndNodes.count):
+      \(reusedNodesCollector.rangeAndNodes.map {$0.1.description}.joined(separator: "\n"))
+      """,
+      file: file,
+      line: line
+    )
+    return
+  }
+
+  for expectedReusedNode in expectedReusedNodes {
+    guard let range = getByteSourceRange(for: expectedReusedNode.source, in: originalString) else {
+      XCTFail("Fail to find string in original source,", file: expectedReusedNode.file, line: expectedReusedNode.line)
+      continue
+    }
+
+    guard let reusedNode = reusedNodesCollector.rangeAndNodes.first(where: { $0.0 == range })?.1 else {
+      XCTFail(
+        """
+        Fail to match the range of \(expectedReusedNode.source) in:
+        \(reusedNodesCollector.rangeAndNodes.map({"\($0.0): \($0.1.description)"}).joined(separator: "\n"))
+        """,
+        file: expectedReusedNode.file,
+        line: expectedReusedNode.line
+      )
+      continue
+    }
+
+    XCTAssertEqual(
+      expectedReusedNode.kind,
+      expectedReusedNode.kind,
+      """
+      Expected \(expectedReusedNode.kind) syntax kind but received \(reusedNode.kind)
+      """,
+      file: expectedReusedNode.file,
+      line: expectedReusedNode.line
+    )
+  }
+}
+
+fileprivate func getByteSourceRange(for substring: String, in sourceString: String) -> ByteSourceRange? {
+  if let range = sourceString.range(of: substring) {
+    return ByteSourceRange(
+      offset: sourceString.utf8.distance(from: sourceString.startIndex, to: range.lowerBound),
+      length: sourceString.utf8.distance(from: range.lowerBound, to: range.upperBound)
+    )
+  }
+  return nil
+}
+
+/// An abstract data structure to describe the how a re-used node produced by the incremental parse should look like.
+public struct ReusedNodeSpec {
+  /// The re-used string in original source without any ``Trivia``
+  let source: String
+  /// The ``SyntaxKind`` of re-used node
+  let kind: SyntaxKind
+  /// The file and line at which this ``ReusedNodeSpec`` was created, so that assertion failures can be reported at its location.
+  let file: StaticString
+  let line: UInt
+
+  public init(
+    _ source: String,
+    kind: SyntaxKind,
+    file: StaticString = #file,
+    line: UInt = #line
+  ) {
+    self.source = source
+    self.kind = kind
+    self.file = file
+    self.line = line
+  }
+}

Tests/SwiftParserTest/IncrementalParsingTests.swift

@@ -18,55 +18,23 @@ import _SwiftSyntaxTestSupport
 public class IncrementalParsingTests: XCTestCase {
 
   public func testIncrementalInvalid() {
-    let source = "struct A⏩️⏸️A⏪️ { func f() {"
-    let (concurrentEdits, originalSubString, editedSubString) = getEditsAndSources(source)
-
-    let originalSource = String(originalSubString)
-    let editedSource = String(editedSubString)
-
-    var tree = Parser.parse(source: originalSource)
-
-    let lookup = IncrementalParseTransition(previousTree: tree, edits: concurrentEdits)
-    tree = Parser.parse(source: editedSource, parseTransition: lookup)
-    XCTAssertEqual("\(tree)", editedSource)
+    assertIncrementalParse(
+      """
+      struct A⏩️⏸️A⏪️ { func f() {
+      """
+    )
   }
 
   public func testReusedNode() throws {
     try XCTSkipIf(true, "Swift parser does not handle node reuse yet")
-
-    let source =
+    assertIncrementalParse(
       """
       struct A⏩️⏸️A⏪️ {}
       struct B {}
-      """
-
-    let (concurrentEdits, originalSubString, editedSubString) = getEditsAndSources(source)
-
-    let originalSource = String(originalSubString)
-    let editedSource = String(editedSubString)
-
-    let origTree = Parser.parse(source: originalSource)
-    let reusedNodeCollector = IncrementalParseReusedNodeCollector()
-    let transition = IncrementalParseTransition(previousTree: origTree, edits: concurrentEdits, reusedNodeDelegate: reusedNodeCollector)
-    let newTree = Parser.parse(source: editedSource, parseTransition: transition)
-    XCTAssertEqual("\(newTree)", editedSource)
-
-    let origStructB = origTree.statements[1]
-    let newStructB = newTree.statements[1]
-    XCTAssertEqual("\(origStructB)", "\nstruct B {}")
-    XCTAssertEqual("\(newStructB)", "\nstruct B {}")
-    XCTAssertNotEqual(origStructB, newStructB)
-
-    XCTAssertEqual(reusedNodeCollector.rangeAndNodes.count, 1)
-    if reusedNodeCollector.rangeAndNodes.count != 1 { return }
-    let (reusedRange, reusedNode) = reusedNodeCollector.rangeAndNodes[0]
-    XCTAssertEqual("\(reusedNode)", "\nstruct B {}")
-
-    XCTAssertEqual(newStructB.byteRange, reusedRange)
-    XCTAssertEqual(origStructB.id, reusedNode.id)
-    XCTAssertEqual(origStructB, reusedNode.as(CodeBlockItemSyntax.self))
-    XCTAssertTrue(reusedNode.is(CodeBlockItemSyntax.self))
-    XCTAssertEqual(origStructB, reusedNode.as(CodeBlockItemSyntax.self)!)
-    XCTAssertEqual(origStructB.parent!.id, reusedNode.parent!.id)
+      """,
+      reusedNodes: [
+        ReusedNodeSpec("struct B {}", kind: .codeBlockItem)
+      ]
+    )
   }
 }