feat: support shift+enter in terminal (#19021)

It acts the same alt+enter, but is more familiar to users.

Closes #18864

site/src/pages/TerminalPage/TerminalPage.test.tsx

@@ -1,5 +1,6 @@
 import "jest-canvas-mock";
 import { waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
 import { API } from "api/api";
 import WS from "jest-websocket-mock";
 import { http, HttpResponse } from "msw";
@@ -148,4 +149,21 @@ describe("TerminalPage", () => {
 		ws.send(text);
 		await expectTerminalText(container, text);
 	});
+
+	it("supports shift+enter", async () => {
+		const ws = new WS(
+			`ws://localhost/api/v2/workspaceagents/${MockWorkspaceAgent.id}/pty`,
+		);
+
+		const { container } = await renderTerminal();
+		// Ideally we could use ws.connected but that seems to pause React updates.
+		// For now, wait for the initial resize message instead.
+		await ws.nextMessage;
+
+		const msg = ws.nextMessage;
+		const terminal = container.getElementsByClassName("xterm");
+		await userEvent.type(terminal[0], "{Shift>}{Enter}{/Shift}");
+		const req = JSON.parse(new TextDecoder().decode((await msg) as Uint8Array));
+		expect(req.data).toBe("\x1b\r");
+	});
 });

site/src/pages/TerminalPage/TerminalPage.tsx

@@ -148,6 +148,25 @@ const TerminalPage: FC = () => {
 			}),
 		);
 
+		// Make shift+enter send ^[^M (escaped carriage return).  Applications
+		// typically take this to mean to insert a literal newline.  There is no way
+		// to remove this handler, so we must attach it once and rely on a ref to
+		// send it to the current socket.
+		const escapedCarriageReturn = "\x1b\r";
+		terminal.attachCustomKeyEventHandler((ev) => {
+			if (ev.shiftKey && ev.key === "Enter") {
+				if (ev.type === "keydown") {
+					websocketRef.current?.send(
+						new TextEncoder().encode(
+							JSON.stringify({ data: escapedCarriageReturn }),
+						),
+					);
+				}
+				return false;
+			}
+			return true;
+		});
+
 		terminal.open(terminalWrapperRef.current);
 
 		// We have to fit twice here. It's unknown why, but the first fit will
@@ -190,6 +209,7 @@ const TerminalPage: FC = () => {
 	}, [navigate, reconnectionToken, searchParams]);
 
 	// Hook up the terminal through a web socket.
+	const websocketRef = useRef<Websocket>();
 	useEffect(() => {
 		if (!terminal) {
 			return;
@@ -270,6 +290,7 @@ const TerminalPage: FC = () => {
 					.withBackoff(new ExponentialBackoff(1000, 6))
 					.build();
 				websocket.binaryType = "arraybuffer";
+				websocketRef.current = websocket;
 				websocket.addEventListener(WebsocketEvent.open, () => {
 					// Now that we are connected, allow user input.
 					terminal.options = {
@@ -333,6 +354,7 @@ const TerminalPage: FC = () => {
 				d.dispose();
 			}
 			websocket?.close(1000);
+			websocketRef.current = undefined;
 		};
 	}, [
 		command,