Add -coverage-prefix-map arg

This is analogous to this change in Driver.cpp swiftlang/swift#32175

Author: keith

Sources/SwiftDriver/Driver/Driver.swift

@@ -296,6 +296,7 @@ public struct Driver {
     self.numParallelJobs = Self.determineNumParallelJobs(&parsedOptions, diagnosticsEngine: diagnosticEngine, env: env)
 
     try Self.validateWarningControlArgs(&parsedOptions)
+    Self.validateCoverageArgs(&parsedOptions, diagnosticsEngine: diagnosticEngine)
 
     // Compute debug information output.
     self.debugInfo = Self.computeDebugInfo(&parsedOptions, diagnosticsEngine: diagnosticEngine)
@@ -1512,6 +1513,16 @@ extension Driver {
       throw Error.conflictingOptions(.warningsAsErrors, .suppressWarnings)
     }
   }
+
+  private static func validateCoverageArgs(_ parsedOptions: inout ParsedOptions, diagnosticsEngine: DiagnosticsEngine) {
+    for coveragePrefixMap in parsedOptions.arguments(for: .coveragePrefixMap) {
+      let value = coveragePrefixMap.argument.asSingle
+      let parts = value.split(separator: "=", maxSplits: 1, omittingEmptySubsequences: false)
+      if parts.count != 2 {
+        diagnosticsEngine.emit(.error_opt_invalid_mapping(option: coveragePrefixMap.option, value: value))
+      }
+    }
+  }
 }
 
 extension Triple {

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -170,6 +170,7 @@ extension Driver {
     try commandLine.appendAll(.sanitizeEQ, from: &parsedOptions)
     try commandLine.appendAll(.debugPrefixMap, from: &parsedOptions)
     try commandLine.appendAllArguments(.Xfrontend, from: &parsedOptions)
+    try commandLine.appendAll(.coveragePrefixMap, from: &parsedOptions)
 
     if let workingDirectory = workingDirectory {
       // Add -Xcc -working-directory before any other -Xcc options to ensure it is

Sources/SwiftOptions/Options.swift

@@ -31,6 +31,7 @@ extension Option {
   public static let colorDiagnostics: Option = Option("-color-diagnostics", .flag, attributes: [.frontend, .doesNotAffectIncrementalBuild], helpText: "Print diagnostics in color")
   public static let compileModuleFromInterface: Option = Option("-compile-module-from-interface", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Treat the (single) input as a swiftinterface and produce a module", group: .modes)
   public static let continueBuildingAfterErrors: Option = Option("-continue-building-after-errors", .flag, attributes: [.frontend, .doesNotAffectIncrementalBuild], helpText: "Continue building, even after errors are encountered")
+  public static let coveragePrefixMap: Option = Option("-coverage-prefix-map", .separate, attributes: [.frontend], helpText: "Remap source paths in coverage info")
   public static let CrossModuleOptimization: Option = Option("-cross-module-optimization", .flag, attributes: [.helpHidden, .frontend], helpText: "Perform cross-module optimization")
   public static let crosscheckUnqualifiedLookup: Option = Option("-crosscheck-unqualified-lookup", .flag, attributes: [.frontend, .noDriver], helpText: "Compare legacy DeclContext- to ASTScope-based unqualified name lookup (for debugging)")
   public static let c: Option = Option("-c", .flag, alias: Option.emitObject, attributes: [.frontend, .noInteractive], group: .modes)
@@ -503,6 +504,7 @@ extension Option {
       Option.colorDiagnostics,
       Option.compileModuleFromInterface,
       Option.continueBuildingAfterErrors,
+      Option.coveragePrefixMap,
       Option.CrossModuleOptimization,
       Option.crosscheckUnqualifiedLookup,
       Option.c,

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -358,6 +358,21 @@ final class SwiftDriverTests: XCTestCase {
     }
   }
 
+  func testCoverageSettings() throws {
+    try assertNoDriverDiagnostics(args: "swiftc", "foo.swift", "-coverage-prefix-map", "foo=bar=baz", "-coverage-prefix-map", "qux=") { driver in
+      let jobs = try driver.planBuild()
+      XCTAssertTrue(jobs[0].commandLine.contains(.flag("-coverage-prefix-map")))
+      XCTAssertTrue(jobs[0].commandLine.contains(.flag("foo=bar=baz")))
+      XCTAssertTrue(jobs[0].commandLine.contains(.flag("-coverage-prefix-map")))
+      XCTAssertTrue(jobs[0].commandLine.contains(.flag("qux=")))
+    }
+
+    try assertDriverDiagnostics(args: "swiftc", "foo.swift", "-coverage-prefix-map", "foo", "-coverage-prefix-map", "bar") {
+      $1.expect(.error("values for '-coverage-prefix-map' must be in the format original=remapped not 'foo'"))
+      $1.expect(.error("values for '-coverage-prefix-map' must be in the format original=remapped not 'bar'"))
+    }
+  }
+
   func testModuleSettings() throws {
     try assertNoDriverDiagnostics(args: "swiftc", "foo.swift") { driver in
       XCTAssertNil(driver.moduleOutputInfo.output)