Merge pull request #2809 from swiftlang/jed/if-defined

Add support for parsing and emitting diagnostics for #if defined(...)

Author: ahoppen

Sources/SwiftIfConfig/IfConfigDiagnostic.swift

@@ -39,6 +39,7 @@ enum IfConfigDiagnostic: Error, CustomStringConvertible {
   case expectedModuleName(syntax: ExprSyntax)
   case badInfixOperator(syntax: ExprSyntax)
   case badPrefixOperator(syntax: ExprSyntax)
+  case unexpectedDefined(syntax: ExprSyntax, argument: String)
 
   var description: String {
     switch self {
@@ -102,6 +103,10 @@ enum IfConfigDiagnostic: Error, CustomStringConvertible {
 
     case .badPrefixOperator:
       return "expected unary '!' expression"
+
+    case .unexpectedDefined:
+      return
+        "compilation conditions in Swift are always boolean and do not need to be checked for existence with 'defined()'"
     }
   }
 
@@ -126,7 +131,8 @@ enum IfConfigDiagnostic: Error, CustomStringConvertible {
       .macabiIsMacCatalyst(syntax: let syntax),
       .expectedModuleName(syntax: let syntax),
       .badInfixOperator(syntax: let syntax),
-      .badPrefixOperator(syntax: let syntax):
+      .badPrefixOperator(syntax: let syntax),
+      .unexpectedDefined(syntax: let syntax, argument: _):
       return Syntax(syntax)
 
     case .unsupportedVersionOperator(name: _, operator: let op):
@@ -207,6 +213,21 @@ extension IfConfigDiagnostic: DiagnosticMessage {
       )
     }
 
+    // For the targetEnvironment(macabi) -> macCatalyst rename we have a Fix-It.
+    if case .unexpectedDefined(syntax: let syntax, argument: let argument) = self {
+      return Diagnostic(
+        node: syntax,
+        message: self,
+        fixIt: .replace(
+          message: SimpleFixItMessage(
+            message: "remove 'defined()'"
+          ),
+          oldNode: syntax,
+          newNode: TokenSyntax.identifier(argument)
+        )
+      )
+    }
+
     return Diagnostic(node: syntax, message: self)
   }
 }

Sources/SwiftIfConfig/IfConfigEvaluation.swift

@@ -313,6 +313,19 @@ func evaluateIfConfig(
         role: "pointer authentication scheme"
       )
 
+    case .defined:
+      guard let argExpr = call.arguments.singleUnlabeledExpression,
+        let arg = argExpr.simpleIdentifierExpr?.name
+      else {
+        return recordError(.unknownExpression(condition))
+      }
+      extraDiagnostics.append(
+        IfConfigDiagnostic.unexpectedDefined(syntax: condition, argument: arg).asDiagnostic
+      )
+      return checkConfiguration(at: condition) {
+        (active: try configuration.isCustomConditionSet(name: arg), syntaxErrorsAllowed: false)
+      }
+
     case ._endian:
       // Ensure that we have a single argument that is a simple identifier.
       guard let argExpr = call.arguments.singleUnlabeledExpression,

Sources/SwiftIfConfig/IfConfigFunctions.swift

@@ -57,6 +57,9 @@ enum IfConfigFunctions: String {
   /// via `_ptrauth(<name>)`.
   case _ptrauth
 
+  /// An unsupported function used by C preprocessor macros (e.g. `#if defined(FOO)`)
+  case defined
+
   /// Whether uses of this function consitutes a check that guards new syntax.
   /// When such a check fails, the compiler should not diagnose syntax errors
   /// within the covered block.
@@ -66,7 +69,7 @@ enum IfConfigFunctions: String {
       return true
 
     case .hasAttribute, .hasFeature, .canImport, .os, .arch, .targetEnvironment,
-      ._hasAtomicBitWidth, ._endian, ._pointerBitWidth, ._runtime, ._ptrauth:
+      ._hasAtomicBitWidth, ._endian, ._pointerBitWidth, ._runtime, ._ptrauth, .defined:
       return false
     }
   }

Tests/SwiftIfConfigTest/EvaluateTests.swift

@@ -457,6 +457,69 @@ public class EvaluateTests: XCTestCase {
       .inactive
     )
   }
+
+  func testDefined() throws {
+    let message =
+      "compilation conditions in Swift are always boolean and do not need to be checked for existence with 'defined()'"
+
+    assertIfConfig(
+      "defined(FOO)",
+      .active,
+      configuration: TestingBuildConfiguration(customConditions: ["FOO"]),
+      diagnostics: [
+        DiagnosticSpec(
+          message: message,
+          line: 1,
+          column: 1,
+          severity: .error,
+          fixIts: [
+            FixItSpec(message: "remove 'defined()'")
+          ]
+        )
+      ]
+    )
+
+    assertIfConfig(
+      "defined(FOO)",
+      .inactive,
+      diagnostics: [
+        DiagnosticSpec(
+          message: message,
+          line: 1,
+          column: 1,
+          severity: .error,
+          fixIts: [
+            FixItSpec(message: "remove 'defined()'")
+          ]
+        )
+      ]
+    )
+
+    assertIfConfig(
+      "defined(FOO) || BAR || defined(BAZ)",
+      .inactive,
+      diagnostics: [
+        DiagnosticSpec(
+          message: message,
+          line: 1,
+          column: 1,
+          severity: .error,
+          fixIts: [
+            FixItSpec(message: "remove 'defined()'")
+          ]
+        ),
+        DiagnosticSpec(
+          message: message,
+          line: 1,
+          column: 24,
+          severity: .error,
+          fixIts: [
+            FixItSpec(message: "remove 'defined()'")
+          ]
+        ),
+      ]
+    )
+  }
 }
 
 /// Assert the results of evaluating the condition within an `#if` against the