Add some test cases

Author: flashspys

Package.swift

@@ -151,6 +151,10 @@ let package = Package(
       name: "SwiftBasicFormatTest",
       dependencies: ["SwiftBasicFormat"]
     ),
+    .testTarget(
+      name: "SwiftDiagnosticsTest",
+      dependencies: ["SwiftDiagnostics", "SwiftParser"]
+    ),
     .testTarget(
       name: "SwiftSyntaxTest",
       dependencies: ["SwiftSyntax", "_SwiftSyntaxTestSupport"]

Sources/SwiftDiagnostics/DiagnosticsFormatter.swift

@@ -77,6 +77,11 @@ public struct DiagnosticsFormatter {
       // print the source line
       annotatedSource.append("\(linePrefix)\(annotatedLine.sourceString)")
 
+      // If the line did not end with \n (e.g. the last line), append it manually
+      if annotatedSource.last != "\n" {
+        annotatedSource.append("\n")
+      }
+      
       let columnsWithDiagnostics = Set(annotatedLine.diagnostics.map { $0.location(converter: slc).column ?? 0 })
       let diagsPerColumn = Dictionary(grouping: annotatedLine.diagnostics) { diag in
         diag.location(converter: slc).column ?? 0

Tests/SwiftDiagnosticsTest/DiagnosticsFormatterTests.swift

@@ -0,0 +1,81 @@
+//===------------------ DiagnosticsFormatterTests.swift -------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 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 XCTest
+@_spi(Testing) import SwiftDiagnostics
+import SwiftParser
+
+final class DiagnosticsFormatterTests: XCTestCase {
+  
+  func annotate(source: String) throws -> String {
+    let tree = try Parser.parse(source: source)
+    let diags = ParseDiagnosticsGenerator.diagnostics(for: tree)
+    return DiagnosticsFormatter.annotatedSource(tree: tree, diags: diags)
+  }
+  
+  func testSingleDiagnostic() throws {
+    let source = """
+    var foo = bar +
+    """
+    let expectedOutput = """
+    1 │ var foo = bar +
+      ∣                ╰─ expected expression in variable
+    
+    """
+    XCTAssertEqual(expectedOutput, try annotate(source: source))
+  }
+  
+  func testMultipleDiagnosticsInOneLine() throws {
+    let source = """
+    foo.[].[].[]
+    """
+    let expectedOutput = """
+    1 │ foo.[].[].[]
+      ∣     │  │  ╰─ expected identifier in member access
+      ∣     │  ╰─ expected identifier in member access
+      ∣     ╰─ expected identifier in member access
+    
+    """
+    XCTAssertEqual(expectedOutput, try annotate(source: source))
+  }
+  
+  func testLineSkipping() throws {
+    let source = """
+    var i = 1
+    i = 2
+    i = foo(
+    i = 4
+    i = 5
+    i = 6
+    i = 7
+    i = 8
+    i = 9
+    i = 10
+    i = bar(
+    """
+    let expectedOutput = """
+     2 │ i = 2
+     3 │ i = foo(
+     4 │ i = 4
+       ∣      ╰─ expected ')' to end function call
+     5 │ i = 5
+     6 │ i = 6
+       ┆
+     9 │ i = 9
+    10 │ i = 10
+    11 │ i = bar(
+       ∣         ├─ expected value in function call
+       ∣         ╰─ expected ')' to end function call
+
+    """
+    XCTAssertEqual(expectedOutput, try annotate(source: source))
+  }
+}