Fix experimental-api-diff command

Author: owenv

Sources/Build/BuildPlan.swift

@@ -1853,11 +1853,22 @@ public class BuildPlan {
         }
     }
 
-    public func createAPIDigesterArgs() -> [String] {
+    public func createAPIToolCommonArgs(includeLibrarySearchPaths: Bool) -> [String] {
         let buildPath = buildParameters.buildPath.pathString
         var arguments = ["-I", buildPath]
 
-        arguments += buildParameters.toolchain.extraSwiftCFlags
+        var extraSwiftCFlags = buildParameters.toolchain.extraSwiftCFlags
+        if !includeLibrarySearchPaths {
+            for index in extraSwiftCFlags.indices.dropLast().reversed() {
+                if extraSwiftCFlags[index] == "-L" {
+                    // Remove the flag
+                    extraSwiftCFlags.remove(at: index)
+                    // Remove the argument
+                    extraSwiftCFlags.remove(at: index)
+                }
+            }
+        }
+        arguments += extraSwiftCFlags
 
         // Add the search path to the directory containing the modulemap file.
         for target in targets {

Sources/Commands/APIDigester.swift

@@ -125,7 +125,7 @@ struct APIDigesterBaselineDumper {
         try apiDigesterTool.dumpSDKJSON(
             at: sdkJSON,
             modules: graph.apiDigesterModules,
-            additionalArgs: buildOp.buildPlan!.createAPIDigesterArgs()
+            additionalArgs: buildOp.buildPlan!.createAPIToolCommonArgs(includeLibrarySearchPaths: false)
         )
 
         return sdkJSON

Sources/Commands/SwiftPackageTool.swift

@@ -311,7 +311,7 @@ extension SwiftPackageTool {
             try apiDigesterTool.dumpSDKJSON(
                 at: currentSDKJSON,
                 modules: packageGraph.apiDigesterModules,
-                additionalArgs: buildOp.buildPlan!.createAPIDigesterArgs()
+                additionalArgs: buildOp.buildPlan!.createAPIToolCommonArgs(includeLibrarySearchPaths: false)
             )
 
             // Dump JSON for the baseline package.

Sources/Commands/SymbolGraphExtract.swift

@@ -42,8 +42,7 @@ public struct SymbolGraphExtract {
             args += ["-module-name", target.c99name]
             args += buildParameters.targetTripleArgs(for: target)
 
-            // FIXME: We should rename this to common Swift tools args or something.
-            args += buildPlan.createAPIDigesterArgs()
+            args += buildPlan.createAPIToolCommonArgs(includeLibrarySearchPaths: true)
             args += ["-module-cache-path", buildParameters.moduleCache.pathString]
 
             args += ["-output-dir", symbolGraphDirectory.pathString]

Tests/CommandsTests/PackageToolTests.swift

@@ -982,6 +982,25 @@ final class PackageToolTests: XCTestCase {
       #endif
     }
 
+    func testAPIDiff() throws {
+        #if os(macOS)
+        guard (try? Resources.default.toolchain.getSwiftAPIDigester()) != nil else {
+            throw XCTSkip("swift-api-digester not available")
+        }
+        fixture(name: "DependencyResolution/External/Simple") { prefix in
+            let packageRoot = prefix.appending(component: "Foo")
+            // Overwrite the existing decl.
+            try localFileSystem.writeFileContents(packageRoot.appending(component: "Foo.swift")) {
+                $0 <<< "public let foo = 42"
+            }
+            let (_, stderr) = try execute(["experimental-api-diff", "1.2.3"], packagePath: packageRoot)
+            XCTAssertTrue(stderr.contains("Func foo() has been removed"))
+        }
+        #else
+        throw XCTSkip("Test unsupported on current platform")
+        #endif
+    }
+
     func testArchiveSource() throws {
         fixture(name: "DependencyResolution/External/Simple") { prefix in
             let packageRoot = prefix.appending(component: "Bar")