Add VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS build setting

When VALIDATE_MODULE_DEPENDENCIES or VALIDATE_HEADER_DEPENDENCIES is set
to YES_ERROR, this new setting can downgrade those errors to warnings.
Since the dependency validation is a new feature that is still evolving,
we need a way to keep it from breaking builds in some contexts.

rdar://157863457

Author: bob-wilson

Sources/SWBCore/Dependencies.swift

@@ -88,8 +88,9 @@ public struct ModuleDependenciesContext: Sendable, SerializableCodable {
     public init?(settings: Settings) {
         let validate = settings.globalScope.evaluate(BuiltinMacros.VALIDATE_MODULE_DEPENDENCIES)
         guard validate != .no else { return nil }
+        let downgrade = settings.globalScope.evaluate(BuiltinMacros.VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS)
         let fixItContext = ModuleDependenciesContext.FixItContext(settings: settings)
-        self.init(validate: validate, moduleDependencies: settings.moduleDependencies, fixItContext: fixItContext)
+        self.init(validate: downgrade ? .yes : validate, moduleDependencies: settings.moduleDependencies, fixItContext: fixItContext)
     }
 
     /// Compute missing module dependencies.
@@ -269,8 +270,9 @@ public struct HeaderDependenciesContext: Sendable, SerializableCodable {
     public init?(settings: Settings) {
         let validate = settings.globalScope.evaluate(BuiltinMacros.VALIDATE_HEADER_DEPENDENCIES)
         guard validate != .no else { return nil }
+        let downgrade = settings.globalScope.evaluate(BuiltinMacros.VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS)
         let fixItContext = HeaderDependenciesContext.FixItContext(settings: settings)
-        self.init(validate: validate, headerDependencies: settings.headerDependencies, fixItContext: fixItContext)
+        self.init(validate: downgrade ? .yes : validate, headerDependencies: settings.headerDependencies, fixItContext: fixItContext)
     }
 
     /// Make diagnostics for missing header dependencies.

Sources/SWBCore/Settings/BuiltinMacros.swift

@@ -1145,6 +1145,7 @@ public final class BuiltinMacros {
     public static let VALIDATE_PLIST_FILES_WHILE_COPYING = BuiltinMacros.declareBooleanMacro("VALIDATE_PLIST_FILES_WHILE_COPYING")
     public static let VALIDATE_PRODUCT = BuiltinMacros.declareBooleanMacro("VALIDATE_PRODUCT")
     public static let VALIDATE_DEPENDENCIES = BuiltinMacros.declareEnumMacro("VALIDATE_DEPENDENCIES") as EnumMacroDeclaration<BooleanWarningLevel>
+    public static let VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS = BuiltinMacros.declareBooleanMacro("VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS")
     public static let VALIDATE_DEVELOPMENT_ASSET_PATHS = BuiltinMacros.declareEnumMacro("VALIDATE_DEVELOPMENT_ASSET_PATHS") as EnumMacroDeclaration<BooleanWarningLevel>
     public static let VALIDATE_HEADER_DEPENDENCIES = BuiltinMacros.declareEnumMacro("VALIDATE_HEADER_DEPENDENCIES") as EnumMacroDeclaration<BooleanWarningLevel>
     public static let VALIDATE_MODULE_DEPENDENCIES = BuiltinMacros.declareEnumMacro("VALIDATE_MODULE_DEPENDENCIES") as EnumMacroDeclaration<BooleanWarningLevel>
@@ -2375,6 +2376,7 @@ public final class BuiltinMacros {
         VALIDATE_CAS_EXEC,
         VALIDATE_PRODUCT,
         VALIDATE_DEPENDENCIES,
+        VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS,
         VALIDATE_DEVELOPMENT_ASSET_PATHS,
         VALIDATE_HEADER_DEPENDENCIES,
         VALIDATE_MODULE_DEPENDENCIES,

Tests/SWBBuildSystemTests/DependencyValidationTests.swift

@@ -546,8 +546,8 @@ fileprivate struct DependencyValidationTests: CoreBasedTests {
         }
     }
 
-    @Test(.requireSDKs(.host), .requireClangFeatures(.printHeadersDirectPerFile), .skipHostOS(.windows, "toolchain too old"), .skipHostOS(.linux, "toolchain too old"))
-    func validateModuleDependenciesMixedSource() async throws {
+    @Test(.requireSDKs(.host), .requireClangFeatures(.printHeadersDirectPerFile), .skipHostOS(.windows, "toolchain too old"), .skipHostOS(.linux, "toolchain too old"), arguments: [false, true])
+    func validateModuleDependenciesMixedSource(downgradeErrors: Bool) async throws {
         try await withTemporaryDirectory { tmpDir async throws -> Void in
             let testWorkspace = try await TestWorkspace(
                 "Test",
@@ -573,6 +573,7 @@ fileprivate struct DependencyValidationTests: CoreBasedTests {
                                     "SWIFT_VERSION": swiftVersion,
                                     "GENERATE_INFOPLIST_FILE": "YES",
                                     "VALIDATE_MODULE_DEPENDENCIES": "YES_ERROR",
+                                    "VALIDATE_DEPENDENCIES_DOWNGRADE_ERRORS": downgradeErrors ? "YES" : "NO",
                                     "SDKROOT": "$(HOST_PLATFORM)",
                                     "SUPPORTED_PLATFORMS": "$(HOST_PLATFORM)",
                                     "DSTROOT": tmpDir.join("dstroot").str,
@@ -615,7 +616,11 @@ fileprivate struct DependencyValidationTests: CoreBasedTests {
             }
 
             try await tester.checkBuild(parameters: BuildParameters(configuration: "Debug"), runDestination: .host, persistent: true) { results in
-                results.checkError(.contains("Missing entries in MODULE_DEPENDENCIES: Accelerate AppKit Foundation"))
+                if downgradeErrors {
+                    results.checkWarning(.contains("Missing entries in MODULE_DEPENDENCIES: Accelerate AppKit Foundation"))
+                } else {
+                    results.checkError(.contains("Missing entries in MODULE_DEPENDENCIES: Accelerate AppKit Foundation"))
+                }
             }
         }
     }