Fix to format ternary expression in BasicFormat

Author: gibachan

Sources/SwiftBasicFormat/BasicFormat.swift

@@ -223,7 +223,6 @@ open class BasicFormat: SyntaxRewriter {
       (.singleQuote, .rawStringDelimiter),  // closing raw string delimiter should never be separate by a space
       (.stringQuote, .rawStringDelimiter),  // closing raw string delimiter should never be separate by a space
       (.stringSegment, _),
-      (_, .colon),
       (_, .comma),
       (_, .ellipsis),
       (_, .eof),
@@ -237,6 +236,13 @@ open class BasicFormat: SyntaxRewriter {
       (_, nil),
       (nil, _):
       return false
+    case (_, .colon):
+      let isTernaryExpr = second?.parent?.is(UnresolvedTernaryExprSyntax.self) == true
+      || second?.parent?.is(TernaryExprSyntax.self) == true
+
+      if !isTernaryExpr {
+        return false
+      }
     case (.leftAngle, _) where second?.tokenKind != .rightAngle:  // `<` and `>` need to be separated by a space because otherwise they become an operator
       return false
     case (_, .rightAngle) where first?.tokenKind != .leftAngle:  // `<` and `>` need to be separated by a space because otherwise they become an operator

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1456,7 +1456,7 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
             FixIt(
               message: InsertTokenFixIt(missingNodes: [Syntax(node.colonMark), Syntax(nextSibling)]),
               changes: [
-                .makePresent(node.colonMark, leadingTrivia: .space),
+                .makePresent(node.colonMark),
                 .makePresent(nextSibling),
               ]
             )

Tests/SwiftSyntaxBuilderTest/TernaryExprTests.swift

@@ -15,7 +15,7 @@ import SwiftSyntax
 import SwiftSyntaxBuilder
 
 final class TernaryExprTests: XCTestCase {
-  func testTernaryExpr() {
+  func testStringLiteralTernaryExpr() {
     let buildable = ExprSyntax("true ? a : b")
     assertBuildResult(
       buildable,
@@ -24,4 +24,32 @@ final class TernaryExprTests: XCTestCase {
       """
     )
   }
+
+  func testTernarySequenceExpr() {
+    let buildable = SequenceExprSyntax {
+      BooleanLiteralExprSyntax(true)
+      UnresolvedTernaryExprSyntax(firstChoice: IntegerLiteralExprSyntax(1))
+      IntegerLiteralExprSyntax(0)
+    }
+    assertBuildResult(
+      buildable,
+      """
+      true ? 1 : 0
+      """
+    )
+  }
+
+  func testTernaryExpr() {
+    let buildable = TernaryExprSyntax(
+      conditionExpression: BooleanLiteralExprSyntax(true),
+      firstChoice: IntegerLiteralExprSyntax(1),
+      secondChoice: IntegerLiteralExprSyntax(0)
+    )
+    assertBuildResult(
+      buildable,
+      """
+      true ? 1 : 0
+      """
+    )
+  }
 }