Disable dataset Save until the form is valid (§05)

src/app/stores/DatasetStore.test.ts

@@ -1,7 +1,12 @@
 import { beforeEach, describe, expect, test } from 'vitest';
 import { createDataset } from '@core/dataset';
 import { createSnippet } from '@core/snippet';
-import { selectSelectedDataset, useDatasetStore, type DatasetForm } from './DatasetStore';
+import {
+  selectCanSave,
+  selectSelectedDataset,
+  useDatasetStore,
+  type DatasetForm,
+} from './DatasetStore';
 import { useSnippetStore } from './SnippetStore';
 
 const store = () => useDatasetStore.getState();
@@ -82,6 +87,45 @@ describe('save — validation', () => {
   });
 });
 
+describe('selectCanSave — drives the Save button disabled state (§05)', () => {
+  const canSaveWith = (patch: Partial<DatasetForm>) => {
+    store().startCreate();
+    store().updateForm(patch);
+    return selectCanSave(useDatasetStore.getState());
+  };
+
+  test('false until a name and valid data are present', () => {
+    store().startCreate();
+    expect(selectCanSave(useDatasetStore.getState())).toBe(false); // empty form
+    expect(canSaveWith({ name: 'Sales' })).toBe(false); // no data
+    expect(canSaveWith({ name: '  ', input: '[{"a":1}]' })).toBe(false); // blank name
+    expect(canSaveWith({ name: 'Sales', input: 'not data' })).toBe(false); // unrecognized
+  });
+
+  test('true for valid inline data and valid URLs', () => {
+    expect(canSaveWith({ name: 'Sales', input: '[{"a":1,"b":2}]' })).toBe(true);
+    expect(canSaveWith({ name: 'Regions', input: 'city,pop\nA,10' })).toBe(true);
+    expect(canSaveWith({ name: 'Remote', source: 'url', input: 'https://x/y.csv' })).toBe(true);
+  });
+
+  test('false for a non-http URL', () => {
+    expect(canSaveWith({ name: 'Bad', source: 'url', input: 'ftp://x/y.csv' })).toBe(false);
+  });
+
+  test('false on a duplicate name, true once the editing dataset keeps its own name', () => {
+    store().add(
+      createDataset({ name: 'Sales', data: [{ a: 1 }], format: 'json', source: 'inline', now: T }),
+    );
+    const id = store().datasets[0].id;
+    // Creating another "Sales" is blocked.
+    expect(canSaveWith({ name: 'Sales', input: '[{"a":1}]' })).toBe(false);
+    // Editing the existing one may keep its own name (excludeId).
+    store().select(id);
+    store().startEdit();
+    expect(selectCanSave(useDatasetStore.getState())).toBe(true);
+  });
+});
+
 describe('save — edit', () => {
   test('updating inline data re-profiles and advances modified', () => {
     store().add(