Fix invalid index check, add api tests

src/public/Terminal.api.ts

@@ -300,6 +300,13 @@ describe('API Integration Tests', () => {
     });
 
     describe('getLine', () => {
+      it('invalid index', async function(): Promise<any> {
+        this.timeout(10000);
+        await openTerminal({ rows: 5 });
+        assert.equal(await page.evaluate(`window.term.buffer.getLine(-1)`), undefined);
+        assert.equal(await page.evaluate(`window.term.buffer.getLine(5)`), undefined);
+      });
+
       it('isWrapped', async function(): Promise<any> {
         this.timeout(10000);
         await openTerminal({ cols: 5 });
@@ -331,7 +338,9 @@ describe('API Integration Tests', () => {
 
       it('getCell', async function(): Promise<any> {
         this.timeout(10000);
-        await openTerminal();
+        await openTerminal({ cols: 5 });
+        assert.equal(await page.evaluate(`window.term.buffer.getLine(0).getCell(-1)`), undefined);
+        assert.equal(await page.evaluate(`window.term.buffer.getLine(0).getCell(5)`), undefined);
         assert.equal(await page.evaluate(`window.term.buffer.getLine(0).getCell(0).char`), '');
         assert.equal(await page.evaluate(`window.term.buffer.getLine(0).getCell(0).width`), 1);
         await page.evaluate(`window.term.write('a文')`);

src/public/Terminal.ts

@@ -180,7 +180,13 @@ class BufferApiView implements IBufferApi {
   public get viewportY(): number { return this._buffer.ydisp; }
   public get baseY(): number { return this._buffer.ybase; }
   public get length(): number { return this._buffer.lines.length; }
-  public getLine(y: number): IBufferLineApi | undefined { return new BufferLineApiView(this._buffer.lines.get(y)); }
+  public getLine(y: number): IBufferLineApi | undefined {
+    const line = this._buffer.lines.get(y);
+    if (!line) {
+      return undefined;
+    }
+    return new BufferLineApiView(line);
+  }
 }
 
 class BufferLineApiView implements IBufferLineApi {
@@ -188,7 +194,7 @@ class BufferLineApiView implements IBufferLineApi {
 
   public get isWrapped(): boolean { return this._line.isWrapped; }
   public getCell(x: number): IBufferCellApi | undefined {
-    if (x < 0 && x >= this._line.length) {
+    if (x < 0 || x >= this._line.length) {
       return undefined;
     }
     return new BufferCellApiView(this._line, x);