Allow diagnostics to have a highlight range

Author: ahoppen

Sources/SwiftDiagnostics/Diagnostic.swift

@@ -19,13 +19,17 @@ public struct Diagnostic: CustomDebugStringConvertible {
   /// The node at whose start location the message should be displayed.
   public let node: Syntax
 
+  /// Nodes that should be highlighted in the source code.
+  public let highlights: [Syntax]
+
   /// Fix-Its that can be applied to resolve this diagnostic.
   /// Each Fix-It offers a different way to resolve the diagnostic. Usually, there's only one.
   public let fixIts: [FixIt]
 
-  public init(node: Syntax, message: DiagnosticMessage, fixIts: [FixIt] = []) {
+  public init(node: Syntax, message: DiagnosticMessage, highlights: [Syntax] = [], fixIts: [FixIt] = []) {
     self.diagMessage = message
     self.node = node
+    self.highlights = highlights
     self.fixIts = fixIts
   }
 

Sources/SwiftParser/Diagnostics/ParseDiagnosticsGenerator.swift

@@ -62,13 +62,13 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
   // MARK: - Private helper functions
 
   /// Produce a diagnostic.
-  private func addDiagnostic<T: SyntaxProtocol>(_ node: T, _ message: DiagnosticMessage, fixIts: [FixIt] = []) {
-    diagnostics.append(Diagnostic(node: Syntax(node), message: message, fixIts: fixIts))
+  private func addDiagnostic<T: SyntaxProtocol>(_ node: T, _ message: DiagnosticMessage, highlights: [Syntax] = [], fixIts: [FixIt] = []) {
+    diagnostics.append(Diagnostic(node: Syntax(node), message: message, highlights: highlights, fixIts: fixIts))
   }
 
   /// Produce a diagnostic.
-  private func addDiagnostic<T: SyntaxProtocol>(_ node: T, _ message: StaticParserError, fixIts: [FixIt] = []) {
-    addDiagnostic(node, message as DiagnosticMessage, fixIts: fixIts)
+  private func addDiagnostic<T: SyntaxProtocol>(_ node: T, _ message: StaticParserError, highlights: [Syntax] = [], fixIts: [FixIt] = []) {
+    addDiagnostic(node, message as DiagnosticMessage, highlights: highlights, fixIts: fixIts)
   }
 
   /// If a diagnostic is generated that covers multiple syntax nodes, mark them as handles so they don't produce the generic diagnostics anymore.
@@ -119,7 +119,20 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     // This is mostly a proof-of-concept implementation to produce more complex diagnostics.
     if let unexpectedCondition = node.body.unexpectedBeforeLeftBrace,
        unexpectedCondition.tokens(withKind: .semicolon).count == 2 {
-      addDiagnostic(node, .cStyleForLoop)
+      // FIXME: This is aweful. We should have a way to either get all children between two cursors in a syntax node or highlight a range from one node to another.
+      addDiagnostic(node, .cStyleForLoop, highlights: ([
+        Syntax(node.pattern),
+        Syntax(node.unexpectedBetweenPatternAndTypeAnnotation),
+        Syntax(node.typeAnnotation),
+        Syntax(node.unexpectedBetweenTypeAnnotationAndInKeyword),
+        Syntax(node.inKeyword),
+        Syntax(node.unexpectedBetweenInKeywordAndSequenceExpr),
+        Syntax(node.sequenceExpr),
+        Syntax(node.unexpectedBetweenSequenceExprAndWhereClause),
+        Syntax(node.whereClause),
+        Syntax(node.unexpectedBetweenWhereClauseAndBody),
+        Syntax(unexpectedCondition)
+      ] as [Syntax?]).compactMap({ $0 }))
       markNodesAsHandled(node.inKeyword.id, unexpectedCondition.id)
     }
     return .visitChildren

Tests/SwiftParserTest/DiagnosticAssertions.swift

@@ -32,15 +32,17 @@ public class FixItApplier: SyntaxRewriter {
 
 /// Asserts that the diagnostics `diag` inside `tree` occurs at `line` and
 /// `column`.
-/// If `message` is not `nil`, assert that the diagnostic has the given message.
 /// If `id` is not `nil`, assert that the diagnostic has the given message.
+/// If `message` is not `nil`, assert that the diagnostic has the given message.
+/// If `highlight` is not `nil`, assert that the highlighted range has this content.
 func XCTAssertDiagnostic<T: SyntaxProtocol>(
   _ diag: Diagnostic,
   in tree: T,
   line: Int,
   column: Int,
   id: MessageID? = nil,
   message: String? = nil,
+  highlight: String? = nil,
   testFile: StaticString = #filePath,
   testLine: UInt = #line
 ) {
@@ -54,6 +56,9 @@ func XCTAssertDiagnostic<T: SyntaxProtocol>(
   if let message = message {
     XCTAssertEqual(diag.message, message, file: testFile, line: testLine)
   }
+  if let highlight = highlight {
+    AssertStringsEqualWithDiff(diag.highlights.map(\.description).joined(), highlight, file: testFile, line: testLine)
+  }
 }
 
 /// Assert that producing diagnostics for `tree` generates a single diagnostic
@@ -67,6 +72,7 @@ func XCTAssertSingleDiagnostic<T: SyntaxProtocol>(
   column: Int,
   id: MessageID? = nil,
   message: String? = nil,
+  highlight: String? = nil,
   expectedFixedSource: String? = nil,
   testFile: StaticString = #filePath,
   testLine: UInt = #line
@@ -76,7 +82,7 @@ func XCTAssertSingleDiagnostic<T: SyntaxProtocol>(
     XCTFail("Received \(diags.count) diagnostics but expected excatly one: \(diags)", file: testFile, line: testLine)
     return
   }
-  XCTAssertDiagnostic(diags.first!, in: tree, line: line, column: column, id: id, message: message, testFile: testFile, testLine: testLine)
+  XCTAssertDiagnostic(diags.first!, in: tree, line: line, column: column, id: id, message: message, highlight: highlight, testFile: testFile, testLine: testLine)
   if let expectedFixedSource = expectedFixedSource {
     let fixedSource = FixItApplier.applyFixes(in: diags, to: tree).description
     AssertStringsEqualWithDiff(fixedSource, expectedFixedSource, file: testFile, line: testLine)

Tests/SwiftParserTest/DiagnosticTests.swift

@@ -31,7 +31,12 @@ public class DiagnosticTests: XCTestCase {
       Syntax(raw: $0.parseForEachStatement().raw).as(ForInStmtSyntax.self)!
     }
 
-    XCTAssertSingleDiagnostic(in: loop, line: 1, column: 1, message: "C-style for statement has been removed in Swift 3")
+    XCTAssertSingleDiagnostic(
+      in: loop,
+      line: 1, column: 1,
+      message: "C-style for statement has been removed in Swift 3",
+      highlight: "let x = 0; x < 10; x += 1, y += 1 "
+    )
   }
 
   public func testMissingClosingParen() throws {