[#2118] Implement keyword snippets for control-flow keywords (if/for/while/etc.)

Sources/SwiftLanguageService/CodeCompletionSession.swift

@@ -501,6 +501,21 @@ class CodeCompletionSession {
       let kind: sourcekitd_api_uid_t? = value[sourcekitd.keys.kind]
       let completionKind = kind?.asCompletionItemKind(sourcekitd.values) ?? .value
 
+      // Check if this is a keyword that should be converted to a snippet
+      var isKeywordSnippet = false
+      if completionKind == .keyword, let snippetText = keywordSnippet(for: name) {
+        let snippetTextEdit = self.computeCompletionTextEdit(
+          completionPos: completionPos,
+          requestPosition: requestPosition,
+          utf8CodeUnitsToErase: utf8CodeUnitsToErase,
+          newText: snippetText,
+          snapshot: snapshot
+        )
+        textEdit = snippetTextEdit
+        insertText = snippetText
+        isKeywordSnippet = true
+      }
+
       if completionKind == .method || completionKind == .function, name.first == "(", name.last == ")" {
         // sourcekitd makes an assumption that the editor inserts a matching `)` when the user types a `(` to start
         // argument completions and thus does not contain the closing parentheses in the insert text. Since we can't
@@ -577,8 +592,8 @@ class CodeCompletionSession {
         deprecated: notRecommended,
         sortText: sortText,
         filterText: filterName,
-        insertText: text,
-        insertTextFormat: isInsertTextSnippet ? .snippet : .plain,
+        insertText: insertText,
+        insertTextFormat: (isInsertTextSnippet || isKeywordSnippet) ? .snippet : .plain,
         textEdit: CompletionItemEdit.textEdit(textEdit),
         data: data.encodeToLSPAny()
       )
@@ -704,6 +719,29 @@ class CodeCompletionSession {
 
     return Position(line: completionPos.line, utf16index: deletionStartUtf16Offset)
   }
+
+  /// Generate a snippet for control flow keywords like if, for, while, etc.
+  /// Returns the snippet text if the keyword is a control flow keyword and snippets are supported, otherwise nil.
+  private func keywordSnippet(for keyword: String) -> String? {
+    guard clientSupportsSnippets else { return nil }
+
+    switch keyword {
+    case "if":
+      return "if ${1:condition} {\n\t${0:}\n}"
+    case "for":
+      return "for ${1:item} in ${2:sequence} {\n\t${0:}\n}"
+    case "while":
+      return "while ${1:condition} {\n\t${0:}\n}"
+    case "guard":
+      return "guard ${1:condition} else {\n\t${0:}\n}"
+    case "switch":
+      return "switch ${1:value} {\n\tcase ${2:pattern}:\n\t\t${0:}\n}"
+    case "repeat":
+      return "repeat {\n\t${0:}\n} while ${1:condition}"
+    default:
+      return nil
+    }
+  }
 }
 
 extension CodeCompletionSession: CustomStringConvertible {

Tests/SourceKitLSPTests/SwiftCompletetionSnippetTests.swift

@@ -0,0 +1,247 @@
+@_spi(SourceKitLSP) import LanguageServerProtocol
+import SKLogging
+import SKTestSupport
+import SourceKitLSP
+import SwiftExtensions
+import XCTest
+
+final class SwiftCompletionSnippetTests: SourceKitLSPTestCase {
+  private var snippetCapabilities = ClientCapabilities(
+    textDocument: TextDocumentClientCapabilities(
+      completion: TextDocumentClientCapabilities.Completion(
+        completionItem: TextDocumentClientCapabilities.Completion.CompletionItem(snippetSupport: true)
+      )
+    )
+  )
+
+  func testKeywordIfProvidesSnippet() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let ifItem = completions.items.first(where: { $0.label == "if" }) else {
+      XCTFail("No completion item with label 'if'")
+      return
+    }
+
+    XCTAssertEqual(ifItem.kind, .keyword)
+    XCTAssertEqual(ifItem.insertTextFormat, .snippet)
+
+    guard let insertText = ifItem.insertText else {
+      XCTFail("Completion item for 'if' has no insertText")
+      return
+    }
+    XCTAssertTrue(insertText.contains("${1:condition}"))
+    XCTAssertTrue(insertText.contains("${0:"))
+  }
+
+  func testKeywordForProvidesSnippet() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let forItem = completions.items.first(where: { $0.label == "for" }) else {
+      XCTFail("No completion item with label 'for'")
+      return
+    }
+
+    XCTAssertEqual(forItem.kind, .keyword)
+    XCTAssertEqual(forItem.insertTextFormat, .snippet)
+
+    guard let insertText = forItem.insertText else {
+      XCTFail("Completion item for 'for' has no insertText")
+      return
+    }
+    XCTAssertTrue(insertText.contains("${1:item}"))
+    XCTAssertTrue(insertText.contains("${2:sequence}"))
+  }
+
+  func testKeywordWhileProvidesSnippet() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let whileItem = completions.items.first(where: { $0.label == "while" }) else {
+      XCTFail("No completion item with label 'while'")
+      return
+    }
+
+    XCTAssertEqual(whileItem.kind, .keyword)
+    XCTAssertEqual(whileItem.insertTextFormat, .snippet)
+
+    guard let insertText = whileItem.insertText else {
+      XCTFail("Completion item for 'while' has no insertText")
+      return
+    }
+    XCTAssertTrue(insertText.contains("${1:condition}"))
+  }
+
+  func testKeywordGuardProvidesSnippet() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let guardItem = completions.items.first(where: { $0.label == "guard" }) else {
+      XCTFail("No completion item with label 'guard'")
+      return
+    }
+
+    XCTAssertEqual(guardItem.kind, .keyword)
+    XCTAssertEqual(guardItem.insertTextFormat, .snippet)
+
+    guard let insertText = guardItem.insertText else {
+      XCTFail("Completion item for 'guard' has no insertText")
+      return
+    }
+    XCTAssertTrue(insertText.contains("${1:condition}"))
+    XCTAssertTrue(insertText.contains("else"))
+  }
+
+  func testKeywordSwitchProvidesSnippet() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let switchItem = completions.items.first(where: { $0.label == "switch" }) else {
+      XCTFail("No completion item with label 'switch'")
+      return
+    }
+
+    XCTAssertEqual(switchItem.kind, .keyword)
+    XCTAssertEqual(switchItem.insertTextFormat, .snippet)
+
+    guard let insertText = switchItem.insertText else {
+      XCTFail("Completion item for 'switch' has no insertText")
+      return
+    }
+    XCTAssertTrue(insertText.contains("${1:value}"))
+    XCTAssertTrue(insertText.contains("case"))
+  }
+
+  func testKeywordRepeatProvidesSnippet() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let repeatItem = completions.items.first(where: { $0.label == "repeat" }) else {
+      XCTFail("No completion item with label 'repeat'")
+      return
+    }
+
+    XCTAssertEqual(repeatItem.kind, .keyword)
+    XCTAssertEqual(repeatItem.insertTextFormat, .snippet)
+
+    guard let insertText = repeatItem.insertText else {
+      XCTFail("Completion item for 'repeat' has no insertText")
+      return
+    }
+    XCTAssertTrue(insertText.contains("while"))
+  }
+
+  func testKeywordWithoutSnippetSupport() async throws {
+    try await SkipUnless.sourcekitdSupportsPlugin()
+
+    // Client without snippet support should get plain keywords
+    let testClient = try await TestSourceKitLSPClient()
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      func test() {
+        1️⃣
+      }
+      """,
+      uri: uri
+    )
+
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+
+    guard let ifItem = completions.items.first(where: { $0.label == "if" }) else {
+      XCTFail("No completion item with label 'if'")
+      return
+    }
+
+    XCTAssertEqual(ifItem.kind, .keyword)
+    XCTAssertEqual(ifItem.insertTextFormat, .plain)
+    XCTAssertEqual(ifItem.insertText, "if")
+  }
+}