fix(config): warn instead of erroring when start dir is not a workspace member (#34458)

When a parent ``deno.json`` declares a ``workspace`` property (including
an empty ``workspace: []``) and Deno is invoked from a child directory
that is not listed as a member, discovery previously errored with
"Config file must be a member of the workspace." That blocks legitimate
setups like a nested ``package.json``-only folder sitting under a Deno
workspace root, even when the user's intent is simply to use the parent
config.

Instead, discard the parent workspace, resolve the start directory as a
standalone workspace, and emit a warning so the user knows the parent
config was ignored. This mirrors the existing silent fallback for npm
workspaces and matches the resolution discussed on the issue.

Fixes #30672

Author: bartlomieju

libs/config/workspace/discovery.rs

@@ -583,16 +583,25 @@ fn handle_workspace_with_members<TSys: FsRead + FsMetadata + FsReadDir>(
     .root_deno_json()
     .map(|d| d.json.workspace.is_some())
     .unwrap_or(false);
-  // if the root was an npm workspace that doesn't have the start config
-  // as a member then only resolve the start config
-  if !is_root_deno_json_workspace
-    && let Some(first_config_folder) = &first_config_folder_url
+  // If the start config folder is not a member of the discovered workspace,
+  // discard the parent workspace and resolve just the start config standalone.
+  // For npm workspaces this is silent backwards-compatible behavior; for deno
+  // workspaces with an explicit "workspace" property we warn so the user knows
+  // the parent config was ignored.
+  if let Some(first_config_folder) = &first_config_folder_url
     && !root_workspace
       .config_folders
       .contains_key(*first_config_folder)
     && let Some(config_folder) =
       found_config_folders.remove(first_config_folder)
   {
+    if is_root_deno_json_workspace {
+      log::warn!(
+        "Warning: config file {} is not a member of the workspace at {}. Ignoring the parent workspace config.",
+        config_folder_config_specifier(&config_folder),
+        root_workspace.root_dir_url(),
+      );
+    }
     let maybe_vendor_dir = resolve_vendor_dir(
       config_folder.deno_json().map(|d| d.as_ref()),
       opts.maybe_vendor_override.as_ref(),

libs/config/workspace/mod.rs

@@ -4958,23 +4958,25 @@ pub mod test {
 
   #[test]
   fn test_deno_member_not_referenced_in_deno_workspace() {
-    fn assert_err(err: &WorkspaceDiscoverError, config_file_path: &Path) {
-      match err.as_kind() {
-        WorkspaceDiscoverErrorKind::ConfigNotWorkspaceMember {
-          workspace_url,
-          config_url,
-        } => {
-          assert_eq!(
-            workspace_url,
-            &url_from_directory_path(&root_dir()).unwrap()
-          );
-          assert_eq!(
-            config_url,
-            &url_from_file_path(config_file_path).unwrap()
-          );
-        }
-        _ => unreachable!(),
-      }
+    // A start directory that has a deno.json but is not a member of the
+    // parent deno workspace falls back to a standalone workspace at the start
+    // directory (a warning is logged about the ignored parent workspace).
+    fn assert_standalone(
+      workspace_dir: &WorkspaceDirectoryRc,
+      config_file_path: &Path,
+    ) {
+      assert_eq!(
+        workspace_dir.workspace.root_dir_path(),
+        config_file_path.parent().unwrap(),
+      );
+      assert_eq!(
+        workspace_dir
+          .workspace
+          .deno_jsons()
+          .map(|c| deno_path_util::url_to_file_path(&c.specifier).unwrap())
+          .collect::<Vec<_>>(),
+        vec![config_file_path.to_path_buf()],
+      );
     }
 
     for file_name in ["deno.json", "deno.jsonc"] {
@@ -4988,20 +4990,21 @@ pub mod test {
       );
       sys.fs_insert_json(root_dir().join("member-a/deno.json"), json!({}));
       sys.fs_insert_json(config_file_path.clone(), json!({}));
-      let err = workspace_at_start_dir_err(&sys, &root_dir().join("member-b"));
-      assert_err(&err, &config_file_path);
+      let workspace_dir =
+        workspace_at_start_dir(&sys, &root_dir().join("member-b"));
+      assert_standalone(&workspace_dir, &config_file_path);
 
       // try for when the config file is specified as well
-      let err = WorkspaceDirectory::discover(
+      let workspace_dir = WorkspaceDirectory::discover(
         &sys,
         WorkspaceDiscoverStart::ConfigFile(&config_file_path),
         &WorkspaceDiscoverOptions {
           discover_pkg_json: true,
           ..Default::default()
         },
       )
-      .unwrap_err();
-      assert_err(&err, &config_file_path);
+      .unwrap();
+      assert_standalone(&workspace_dir, &config_file_path);
     }
   }
 
@@ -5085,16 +5088,40 @@ pub mod test {
     );
     sys.fs_insert_json(root_dir().join("member/deno.json"), json!({}));
     sys.fs_insert_json(root_dir().join("package/package.json"), json!({}));
-    // npm package needs to be a member of the deno workspace
-    let err = workspace_at_start_dir_err(&sys, &root_dir().join("package"));
+    // The start folder is not referenced by the parent deno workspace, so the
+    // parent workspace is discarded and the start folder is resolved on its
+    // own (a warning is logged for the deno workspace case).
+    let workspace_dir =
+      workspace_at_start_dir(&sys, &root_dir().join("package"));
     assert_eq!(
-      err.to_string(),
-      normalize_err_text(
-        "Config file must be a member of the workspace.
-  Config: [ROOT_DIR_URL]/package/package.json
-  Workspace: [ROOT_DIR_URL]/"
-      )
+      workspace_dir.workspace.root_dir_path(),
+      root_dir().join("package"),
     );
+    assert_eq!(workspace_dir.workspace.deno_jsons().count(), 0);
+    assert_eq!(workspace_dir.workspace.package_jsons().count(), 1);
+  }
+
+  #[test]
+  fn test_npm_package_under_deno_workspace_with_empty_members() {
+    // Exact repro from #30672: parent deno.json has an empty `workspace` array
+    // and the start folder contains only a package.json. The parent workspace
+    // should be discarded and the start folder resolved standalone.
+    let sys = InMemorySys::default();
+    sys.fs_insert_json(
+      root_dir().join("deno.json"),
+      json!({
+        "workspace": []
+      }),
+    );
+    sys.fs_insert_json(root_dir().join("package/package.json"), json!({}));
+    let workspace_dir =
+      workspace_at_start_dir(&sys, &root_dir().join("package"));
+    assert_eq!(
+      workspace_dir.workspace.root_dir_path(),
+      root_dir().join("package"),
+    );
+    assert_eq!(workspace_dir.workspace.deno_jsons().count(), 0);
+    assert_eq!(workspace_dir.workspace.package_jsons().count(), 1);
   }
 
   #[test]

tests/specs/workspaces/parent_workspace_empty_ignored/__test__.jsonc

@@ -0,0 +1,9 @@
+{
+  "tests": {
+    "child_dir_not_in_workspace": {
+      "cwd": "child",
+      "args": "run main.ts",
+      "output": "child/main.out"
+    }
+  }
+}

tests/specs/workspaces/parent_workspace_empty_ignored/child/main.out

@@ -0,0 +1,2 @@
+Warning: config file [WILDLINE] is not a member of the workspace at [WILDLINE]. Ignoring the parent workspace config.
+hello from child

tests/specs/workspaces/parent_workspace_empty_ignored/child/main.ts

@@ -0,0 +1 @@
+console.log("hello from child");

tests/specs/workspaces/parent_workspace_empty_ignored/child/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "child",
+  "version": "1.0.0"
+}

tests/specs/workspaces/parent_workspace_empty_ignored/deno.json

@@ -0,0 +1,3 @@
+{
+  "workspace": []
+}