Improve diagnostic when automatic resolution is disabled (#3639)

- Show the exact path where we looked for a resolved file
- Special case if there wasn't a file to begin with

rdar://81172549

(cherry picked from commit 9b9bed7)

Author: neonichu

Sources/Workspace/Workspace.swift

@@ -1859,7 +1859,11 @@ extension Workspace {
         )
 
         if precomputationResult.isRequired {
-            diagnostics.emit(error: "cannot update Package.resolved file because automatic resolution is disabled")
+            if !fileSystem.exists(resolvedFile) {
+                diagnostics.emit(error: "a resolved file is required when automatic dependency resolution is disabled and should be placed at \(resolvedFile.pathString)")
+            } else {
+                diagnostics.emit(error: "an out-of-date resolved file was detected at \(resolvedFile.pathString), which is not allowed when automatic dependency resolution is disabled; please make sure to update the file to reflect the changes in dependencies")
+            }
         }
 
         try self.updateBinaryArtifacts(manifests: currentManifests, addedOrUpdatedPackages: [], diagnostics: diagnostics)

Tests/WorkspaceTests/WorkspaceTests.swift

@@ -3690,7 +3690,7 @@ final class WorkspaceTests: XCTestCase {
         // Check force resolve. This should produce an error because the resolved file is out-of-date.
         workspace.checkPackageGraphFailure(roots: ["Root"], forceResolvedVersions: true) { diagnostics in
             DiagnosticsEngineTester(diagnostics) { result in
-                result.check(diagnostic: "cannot update Package.resolved file because automatic resolution is disabled", checkContains: true, behavior: .error)
+                result.check(diagnostic: "an out-of-date resolved file was detected at /tmp/ws/Package.resolved, which is not allowed when automatic dependency resolution is disabled; please make sure to update the file to reflect the changes in dependencies", checkContains: true, behavior: .error)
             }
         }
         workspace.checkManagedDependencies { result in
@@ -3729,6 +3729,57 @@ final class WorkspaceTests: XCTestCase {
         }
     }
 
+    func testForceResolveWithNoResolvedFile() throws {
+        let sandbox = AbsolutePath("/tmp/ws/")
+        let fs = InMemoryFileSystem()
+
+        let workspace = try MockWorkspace(
+            sandbox: sandbox,
+            fs: fs,
+            roots: [
+                MockPackage(
+                    name: "Root",
+                    targets: [
+                        MockTarget(name: "Root", dependencies: ["Foo", "Bar"]),
+                    ],
+                    products: [],
+                    dependencies: [
+                        .git(name: "Foo", requirement: .upToNextMajor(from: "1.0.0")),
+                        .git(name: "Bar", requirement: .upToNextMajor(from: "1.0.0")),
+                    ]
+                ),
+            ],
+            packages: [
+                MockPackage(
+                    name: "Foo",
+                    targets: [
+                        MockTarget(name: "Foo"),
+                    ],
+                    products: [
+                        MockProduct(name: "Foo", targets: ["Foo"]),
+                    ],
+                    versions: ["1.0.0", "1.2.0", "1.3.2"]
+                ),
+                MockPackage(
+                    name: "Bar",
+                    targets: [
+                        MockTarget(name: "Bar"),
+                    ],
+                    products: [
+                        MockProduct(name: "Bar", targets: ["Bar"]),
+                    ],
+                    versions: ["1.0.0", "develop"]
+                ),
+            ]
+        )
+
+        workspace.checkPackageGraphFailure(roots: ["Root"], forceResolvedVersions: true) { diagnostics in
+            DiagnosticsEngineTester(diagnostics) { result in
+                result.check(diagnostic: "a resolved file is required when automatic dependency resolution is disabled and should be placed at /tmp/ws/Package.resolved", checkContains: true, behavior: .error)
+            }
+        }
+    }
+
     func testForceResolveToResolvedVersionsLocalPackage() throws {
         let sandbox = AbsolutePath("/tmp/ws/")
         let fs = InMemoryFileSystem()