Do not crash on invalid file URLs (#5795)

rdar://100738993

Author: neonichu

Sources/PackageLoading/ManifestJSONParser.swift

@@ -231,7 +231,7 @@ enum ManifestJSONParser {
                 "file:// URLs with hostnames are not supported, are you missing a '/'?", diagnosticFile: nil
               )
             }
-            return AbsolutePath(location).pathString
+            return try AbsolutePath(validating: location).pathString
         } else if parseScheme(dependencyLocation) == nil {
             // If the URL has no scheme, we treat it as a path (either absolute or relative to the base URL).
             switch packageKind {

Tests/PackageLoadingTests/PD_4_2_LoadingTests.swift

@@ -508,25 +508,38 @@ class PackageDescription4_2LoadingTests: PackageDescriptionLoadingTests {
         }
     }
 
-    func testFileURLsWithHostnames() throws {
+    func testFileURLErrors() throws {
         enum ExpectedError {
+          case invalidAbsolutePath
           case relativePath
           case unsupportedHostname
 
-          var manifestError: ManifestParseError {
+          var manifestError: ManifestParseError? {
             switch self {
+            case .invalidAbsolutePath:
+              return nil
             case .relativePath:
               return .invalidManifestFormat("file:// URLs cannot be relative, did you mean to use '.package(path:)'?", diagnosticFile: nil)
             case .unsupportedHostname:
               return .invalidManifestFormat("file:// URLs with hostnames are not supported, are you missing a '/'?", diagnosticFile: nil)
             }
           }
+
+          var pathError: TSCBasic.PathValidationError? {
+            switch self {
+            case .invalidAbsolutePath:
+              return .invalidAbsolutePath("")
+            default:
+              return nil
+            }
+          }
         }
 
         let urls: [(String, ExpectedError)] = [
           ("file://../best", .relativePath), // Possible attempt at a relative path.
           ("file://somehost/bar", .unsupportedHostname), // Obviously non-local.
           ("file://localhost/bar", .unsupportedHostname), // Local but non-trivial (e.g. on Windows, this is a UNC path).
+          ("file://", .invalidAbsolutePath) // Invalid path.
         ]
         for (url, expectedError) in urls {
             let content = """
@@ -546,7 +559,14 @@ class PackageDescription4_2LoadingTests: PackageDescriptionLoadingTests {
 
             let observability = ObservabilitySystem.makeForTesting()
             XCTAssertThrowsError(try loadAndValidateManifest(content, observabilityScope: observability.topScope), "expected error") { error in
-                XCTAssertEqual(error as? ManifestParseError, expectedError.manifestError)
+                switch error {
+                case is ManifestParseError:
+                    XCTAssertEqual(error as? ManifestParseError, expectedError.manifestError)
+                case is TSCBasic.PathValidationError:
+                    XCTAssertEqual(error.localizedDescription, expectedError.pathError?.localizedDescription)
+                default:
+                    XCTFail("unhandled error type: \(error)")
+                }
             }
         }
     }