Very basic build setting validation

Package.resolved

@@ -42,7 +42,7 @@
       "location" : "https://github.com/mattmassicotte/XCConfig",
       "state" : {
         "branch" : "main",
-        "revision" : "26059718eab7a4fa723dd75cde45cf099d3e75a8"
+        "revision" : "ffe291c9237407f3f2695d10e567df63ad8b81fd"
       }
     },
     {

Sources/XCLinting/Extensions/PBXProj+BuildSettings.swift

@@ -0,0 +1,19 @@
+import Foundation
+
+import XcodeProj
+
+extension PBXProj {
+	func enumerateBuildConfigurations(_ block: (String, XCConfigurationList) throws -> Void) rethrows {
+		for target in legacyTargets {
+			guard let list = target.buildConfigurationList else { continue }
+
+			try block(target.name, list)
+		}
+
+		for target in nativeTargets {
+			guard let list = target.buildConfigurationList else { continue }
+
+			try block(target.name, list)
+		}
+	}
+}

Sources/XCLinting/Rules/ValidateBuildSettingsRule.swift

@@ -0,0 +1,48 @@
+import Foundation
+
+import XcodeProj
+import XCConfig
+
+/// Detect build settings that are deprecated or no longer functional.
+///
+/// This currently runs a superficial check. It does not perform configuration evaluation yet.
+struct ValidateBuildSettingsRule {
+	func run(_ environment: XCLinter.Environment) throws -> [Violation] {
+		var violations = [Violation]()
+
+		// check top-level
+		for config in environment.project.pbxproj.buildConfigurations {
+			violations.append(contentsOf: evaluateTargetSettings("Project", config: config))
+		}
+
+		// check targets
+		environment.project.pbxproj.enumerateBuildConfigurations { name, configList in
+			for config in configList.buildConfigurations {
+				violations.append(contentsOf: evaluateTargetSettings(name, config: config))
+			}
+		}
+
+		return violations
+	}
+
+	func evaluateTargetSettings(_ name: String, config: XCBuildConfiguration) -> [Violation] {
+		var violations = [Violation]()
+
+		for pair in config.buildSettings {
+			guard let setting = BuildSetting(rawValue: pair.key) else { continue }
+
+			let status = setting.evaluateValue(pair.value as? String ?? "")
+
+			switch status {
+			case .deprecated:
+				violations.append(.init("\(name):\(pair.key) = \(pair.value) is deprecated"))
+			case .invalid:
+				violations.append(.init("\(name):\(pair.key) = \(pair.value) is invalid"))
+			case .valid:
+				break
+			}
+		}
+
+		return violations
+	}
+}

Sources/XCLinting/Violation.swift

@@ -1,9 +1,9 @@
 import XcodeProj
 
-public struct Violation {
+public struct Violation: Hashable {
 	public var message: String
 	public var objects: [PBXObject]
-	
+
 	public init(_ message: String, objects: [PBXObject] = []) {
 		self.message = message
 		self.objects = objects

Sources/XCLinting/XCLinter.swift

@@ -66,7 +66,8 @@ extension XCLinter.Environment {
 
 extension XCLinter {
 	public static let defaultRuleIdentifiers: Set<String> = [
-		"build_files_ordered"
+		"build_files_ordered",
+		"validate_build_settings",
 	]
 
 	public static let defaultRules: [Rule] = Array(ruleMap.filter({ defaultRuleIdentifiers.contains($0.0) }).values)
@@ -76,5 +77,6 @@ extension XCLinter {
 		"embedded_build_setting": embeddedBuildSettingsRule,
 		"build_files_ordered": { try BuildFilesAreOrderedRule().run($0) },
 		"groups_sorted": groupsAreSortedRule,
+		"validate_build_settings": { try ValidateBuildSettingsRule().run($0) },
 	]
 }

Tests/XCLintTests/Bundle+TestData.swift

@@ -0,0 +1,15 @@
+import Foundation
+import XCTest
+
+extension Bundle {
+	func testDataURL(named: String) throws -> URL {
+		let bundle = Bundle.module
+
+		let resourceURL = try XCTUnwrap(bundle.resourceURL)
+
+		return resourceURL
+			.appendingPathComponent("TestData", isDirectory: true)
+			.appendingPathComponent(named)
+			.standardizedFileURL
+	}
+}

Tests/XCLintTests/EmbeddedBuildSettingsRuleTests.swift

@@ -3,19 +3,6 @@ import XCTest
 @testable import XCLinting
 import XcodeProj
 
-extension Bundle {
-	func testDataURL(named: String) throws -> URL {
-		let bundle = Bundle.module
-
-		let resourceURL = try XCTUnwrap(bundle.resourceURL)
-
-		return resourceURL
-			.appendingPathComponent("TestData", isDirectory: true)
-			.appendingPathComponent(named)
-			.standardizedFileURL
-	}
-}
-
 final class EmbeddedBuildSettingsRuleTests: XCTestCase {
 	func testProjectWithBuildSettings() throws {
 		let url = try Bundle.module.testDataURL(named: "StockMacOSApp.xcodeproj")