editor: fixed tabs-insert-spaces

test/unit/testtabs.ts

@@ -0,0 +1,44 @@
+import assert from "assert";
+import { describe } from "mocha";
+import { indentUnit } from "@codemirror/language";
+import { EditorState } from "@codemirror/state";
+import { spacesToTabStop } from "../../src/ide/views/tabs";
+
+// Build a state from text with '|' marking the cursor; returns the spaces Tab would insert.
+function tabAt(textWithCursor: string, tabSize: number, unit: number): string {
+    const head = textWithCursor.indexOf('|');
+    const state = EditorState.create({
+        doc: textWithCursor.replace('|', ''),
+        extensions: [EditorState.tabSize.of(tabSize), indentUnit.of(" ".repeat(unit))],
+    });
+    return spacesToTabStop(state, head);
+}
+
+describe('spacesToTabStop', () => {
+    it('should advance by indent unit in leading whitespace', () => {
+        assert.strictEqual(tabAt('|', 8, 2).length, 2);
+        assert.strictEqual(tabAt('  |', 8, 2).length, 2);
+        assert.strictEqual(tabAt('    |x', 8, 2).length, 2);
+        assert.strictEqual(tabAt('   |x', 8, 2).length, 1); // 3 -> 4
+    });
+    it('should advance to tab size stops after text', () => {
+        assert.strictEqual(tabAt('int x;|', 8, 2).length, 2); // 6 -> 8
+        assert.strictEqual(tabAt('int x;  |', 8, 2).length, 8); // 8 -> 16
+        assert.strictEqual(tabAt('x|', 8, 2).length, 7);
+    });
+    it('should use the tab size stops when indent unit equals it', () => {
+        assert.strictEqual(tabAt('|', 8, 8).length, 8);
+        assert.strictEqual(tabAt('  |', 8, 8).length, 6);
+    });
+    it('should count literal tab characters as tab size columns', () => {
+        assert.strictEqual(tabAt('\t|', 8, 2).length, 2); // col 8 -> 10
+        assert.strictEqual(tabAt('\tx|', 8, 2).length, 7); // col 9 -> 16
+    });
+    it('should use the cursor line only', () => {
+        assert.strictEqual(tabAt('    foo\n|', 8, 2).length, 2);
+        assert.strictEqual(tabAt('a\n  b|\nc', 4, 2).length, 1); // col 3 -> 4
+    });
+    it('should insert spaces only', () => {
+        assert.strictEqual(tabAt('a|', 4, 2), '   ');
+    });
+});