[debug] Theia does not stop on breakpoints with the debugger provided by the vscode.mock-debug extension

[kittaakos]

Bug Description:

Steps to Reproduce:

1. Build the vscode.mock-debug extension from their repo. Alternatively, you can follow the steps from vscode: add support for debug/toolbar, debug/variables/context menus contribution and debugState when clause context  #11871 and get the mock-debug VS Code extension from my fork.
2. Open the sampleWorkspace folder from the repo as a workspace in Theia.
3. Set a breakpoint to line 11,
4. Start the Debug readme.md file,
5. Debugger stops on entry,
6. Continue,
7. Debugger does not stop on line 11, instead it falls to the end of the readme.

VS Code:

stop_breakpoint_vscode.mp4

Theia:

stop_breakpoint_theia.mp4

When the debugger session starts in Theia, I see the following error in the logs. I do not know if it's related to this bug:

logger-protocol.ts:113 2022-11-18T15:27:58.287Z root ERROR Error setting breakpoints: Cannot read properties of undefined (reading 'breakpoints')
log @ logger-protocol.ts:113
(anonymous) @ logger-frontend-module.ts:42
(anonymous) @ logger.ts:312
(anonymous) @ logger.ts:304
Promise.then (async)
log @ logger.ts:299
log @ logger.ts:45
sendFunctionBreakpoints @ debug-session.tsx:683
async function (async)
sendFunctionBreakpoints @ debug-session.tsx:671
updateBreakpoints @ debug-session.tsx:645
async function (async)
updateBreakpoints @ debug-session.tsx:649
configure @ debug-session.tsx:325
(anonymous) @ debug-session.tsx:121
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
doFire @ debug-session-connection.ts:331
handleEvent @ debug-session-connection.ts:312
handleMessage @ debug-session-connection.ts:265
(anonymous) @ debug-session-connection.ts:171
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
fireMessageReceived @ connection.ts:37
$sendMessage @ connection.ts:82
doInvokeHandler @ rpc-protocol.ts:287
invokeHandler @ rpc-protocol.ts:272
receiveRequest @ rpc-protocol.ts:231
receiveOneMessage @ rpc-protocol.ts:192
(anonymous) @ rpc-protocol.ts:101
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
(anonymous) @ rpc-protocol.ts:343
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
(anonymous) @ hosted-plugin.ts:540
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
postMessage @ hosted-plugin-watcher.ts:35
onRequest @ proxy-factory.ts:167
(anonymous) @ proxy-factory.ts:146
handleRequest @ rpc-protocol.ts:188
handleMessage @ rpc-protocol.ts:86
(anonymous) @ rpc-protocol.ts:75
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
handleData @ channel.ts:239
handleMessage @ channel.ts:197
(anonymous) @ channel.ts:155
(anonymous) @ event.ts:128
invoke @ event.ts:136
fire @ event.ts:279
(anonymous) @ web-socket-channel.ts:38
(anonymous) @ ws-connection-provider.ts:84
Emitter.emit @ index.mjs:136
emitEvent @ socket.js:385
onevent @ socket.js:372
onpacket @ socket.js:340
Emitter.emit @ index.mjs:136
(anonymous) @ manager.js:240
Promise.then (async)
(anonymous) @ websocket-constructor.browser.js:8
ondecoded @ manager.js:239
Emitter.emit @ index.mjs:136
add @ index.js:148
ondata @ manager.js:226
Emitter.emit @ index.mjs:136
onPacket @ socket.js:348
Emitter.emit @ index.mjs:136
onPacket @ transport.js:114
onData @ transport.js:106
ws.onmessage @ websocket.js:87
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Additional Information

• Operating System: macOS, 12.5.1
• Theia Version: fe8e4c1

[kittaakos]

According to the debug adapter protocol, the SetFunctionBreakpoints response always has a body and breakpoints, but in reality, it does not. VS Code has a guard against it, and adding a guard here plus providing the lines solves the issue:

11885_stop_breakpoint.mp4

[kittaakos]

Please assign the issue to me.