feat(workbench): Open files from Finder in the single-file window (#152)

On macOS, OpenIDEA is now listed under Finder's Open With for text and source files and for folders. It never becomes the default app for any of them: all document types are declared with rank Alternate, and only in tauri.macos.conf.json, so Windows and Linux installers register nothing.

Files opened from Finder, the Dock or a second instance share one routing path (plan_open). A file inside a local project that is already open, or still opening, goes to that project's window, choosing the deepest root when projects are nested. Any other file goes to the existing single-file window, or to a new one. A folder focuses the window that already has it open, otherwise it opens as a project. Paths that arrive before setup are queued and opened with the first launch.

The single-file window now closes with its last tab, restores its files the next time it opens, and only offers Open File and drop hints when empty. Also fixes a regression: reopening projects on startup no longer replaces a file opened at cold start.

Refs #128

src/workbench/EditorArea.tsx

@@ -1,11 +1,14 @@
 import { executeAction, useActions } from "@/platform/actions";
 import { shortcutLabel } from "@/platform/keymap";
+import { useProject } from "@/platform/project";
 import { T } from "@/ui";
 import { useWorkbenchSlots } from "./contributions";
 import { ErrorBoundary, Slot } from "./ErrorBoundary";
 import styles from "./EditorArea.module.css";
 
-const HINTS: Array<{ label: string; action?: string; fallback?: string }> = [
+type Hint = { label: string; action?: string; fallback?: string };
+
+const HINTS: Hint[] = [
   { label: "Search Everywhere", action: "navigate.searchEverywhere", fallback: "Double ⇧" },
   { label: "Go to File", action: "navigate.gotoFile" },
   { label: "Recent Files", action: "navigate.recentFiles" },
@@ -13,13 +16,20 @@ const HINTS: Array<{ label: string; action?: string; fallback?: string }> = [
   { label: "Drop files here to open them" },
 ];
 
+/** LightEdit has no project to navigate: only opening files works there. */
+const LIGHT_EDIT_HINTS: Hint[] = [
+  { label: "Open File", action: "file.openFile" },
+  { label: "Drop files here to open them" },
+];
+
 /** IDEA's empty editor: a few navigation hints with their shortcuts. */
 export function EmptyEditor() {
   const actions = useActions((s) => s.actions);
+  const lightEdit = useProject((s) => s.lightEdit);
   return (
     <div className={styles.empty}>
       <dl className={styles.hints}>
-        {HINTS.map((h) => {
+        {(lightEdit ? LIGHT_EDIT_HINTS : HINTS).map((h) => {
           const keys = h.action ? (shortcutLabel(h.action) ?? h.fallback) : undefined;
           const runnable = !!h.action && actions.has(h.action);
           return (

src/workbench/lightEdit.test.tsx

@@ -5,6 +5,7 @@ import { evaluateWhen } from "@/platform/context";
 import { useProject } from "@/platform/project";
 import { activateWorkbench } from "./activate";
 import { registerStatusItem, registerTitleItem, registerToolWindow } from "./contributions";
+import { EmptyEditor } from "./EditorArea";
 import { chooseProjectWindow } from "./projectWindow";
 import { Workbench } from "./Workbench";
 
@@ -51,6 +52,21 @@ describe("LightEdit window", () => {
     expect(screen.queryByText("Welcome to OpenIDEA")).toBeNull();
   });
 
+  it("hints only at opening files in an empty editor", () => {
+    render(<EmptyEditor />);
+    expect(screen.getByText("Open File")).toBeInTheDocument();
+    expect(screen.getByText("Drop files here to open them")).toBeInTheDocument();
+    for (const project of ["Search Everywhere", "Go to File", "Recent Files", "Navigation Bar"])
+      expect(screen.queryByText(project)).toBeNull();
+  });
+
+  it("keeps the navigation hints in a project window", () => {
+    useProject.setState({ lightEdit: false });
+    render(<EmptyEditor />);
+    expect(screen.getByText("Go to File")).toBeInTheDocument();
+    expect(screen.queryByText("Open File")).toBeNull();
+  });
+
   it("sets the context keys that keep project actions off", () => {
     const dispose = activateWorkbench();
     expect(evaluateWhen("lightEdit")).toBe(true);