Implementation for debug-isolated flag and streaming func CLI output #4765

nturinski · 2025-10-24T18:02:45Z

This pull request introduces support for streaming terminal output from Azure Functions host tasks, enabling consumers of the API to access real-time output from running processes.

~~It adds a new async string stream utility, integrates this stream into the function task lifecycle, and exposes the stream through the API.~~

Additionally, it improves handling for .NET isolated debug scenarios by extracting process IDs from terminal output if the flag is set.

Minor updates were made to the package configuration to support these features, including func tasks now support the args property since --debug-isolate is ugly to write all in the command.

~~Configuration Updates~~

* Added the enabledApiProposals section to package.json to enable the terminalDataWriteEvent API, which is required for capturing terminal output.

EDIT: To read the stream, you can run this snippet:

for await (const chunk of runningFuncTaskItem.stream) {
                    // Process each chunk of the stream
                    console.log(chunk);
                }

Copilot

Pull Request Overview

This PR adds support for streaming terminal output from Azure Functions host tasks and improves debugging for .NET isolated functions. The main purpose is to enable real-time access to process output and automatically extract process IDs from terminal output when using the --dotnet-isolated-debug flag.

Key changes:

Introduces an async string stream utility for capturing and consuming terminal output
Integrates streaming into the function task lifecycle and exposes it through the API
Adds support for extracting process IDs from JSON-formatted terminal output in .NET isolated debug mode

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/utils/stream.ts	New async string stream utility for managing terminal output
src/funcCoreTools/funcHostTask.ts	Integrates stream handler into task lifecycle and ensures cleanup on task termination
src/debug/FuncTaskProvider.ts	Adds support for passing additional arguments to func tasks
src/commands/pickFuncProcess.ts	Implements terminal output streaming and PID extraction for debug mode
package.json	Enables terminalDataWriteEvent API and adds args property to task definition

src/utils/stream.ts

Copilot · 2025-10-24T18:06:22Z

src/commands/pickFuncProcess.ts

+                    vscode.window.onDidWriteTerminalData(async (event: vscode.TerminalDataWriteEvent) => {
+                        const terminal = vscode.window.terminals.find(t => funcTask.name === t.name);
+                        if (event.terminal === terminal) {
+                            taskInfo.streamHandler.write(event.data);
+                        }
+                    });


The event listener created by onDidWriteTerminalData is never disposed, causing a resource leak. Store the returned Disposable and dispose it when the task completes or errors.

Co-authored-by: Copilot <[email protected]>

…ft/vscode-azurefunctions into nat/fileBasedPickProcess

Copilot

Pull Request Overview

Copilot reviewed 5 out of 6 changed files in this pull request and generated 5 comments.

src/debug/FuncTaskProvider.ts

Copilot · 2025-10-24T19:01:18Z

src/commands/pickFuncProcess.ts

        const funcPort: string = await getFuncPortFromTaskOrProject(context, funcTask, workspaceFolder);
        let statusRequestTimeout: number = intervalMs;
        const maxTime: number = Date.now() + timeoutInSeconds * 1000;
+        const debugModeOn = funcTask.name.includes('--dotnet-isolated-debug') && funcTask.name.includes('--enable-json-output');


Checking for command-line flags in the task name is fragile and unclear. Task names are meant for display purposes. Consider checking the actual command line or task definition properties instead.

Copilot · 2025-10-24T19:01:18Z

src/commands/pickFuncProcess.ts

+async function setEventPidByJsonOutput(taskInfo: IRunningFuncTask, taskName: string): Promise<vscode.Disposable> {
+    const setPidByJsonOutputListener = vscode.window.onDidWriteTerminalData(async (event: vscode.TerminalDataWriteEvent) => {
+        const terminal = vscode.window.terminals.find(t => taskName === t.name);
+        if (event.terminal === terminal) {
+            if (event.data.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {
+                const matches = event.data.match(/"workerProcessId"\s*:\s*(\d+)/);
+                if (matches && matches.length > 1) {
+                    taskInfo.processId = Number(matches[1]);
+                    setPidByJsonOutputListener.dispose();
+                }
+            }
+        }
+    });


The listener mutates taskInfo.processId without synchronization. If terminal data arrives concurrently while the main loop in startFuncTask checks taskInfo.processId !== parentPid, there's a potential race condition where the PID could be updated between the check and the return statement.

Copilot · 2025-10-24T19:01:18Z

src/funcCoreTools/funcHostTask.ts

+            const outputReader = vscode.window.onDidWriteTerminalData(async (event: vscode.TerminalDataWriteEvent) => {
+                const terminal = vscode.window.terminals.find(t => terminalName === t.name);
+                if (event.terminal === terminal) {
+                    runningFuncTask.streamHandler.write(event.data);
+                }
+            });


Variable runningFuncTask is referenced before it's declared on line 107. This will cause a ReferenceError at runtime. Move the declaration of runningFuncTask before the outputReader initialization.

Copilot · 2025-10-24T19:01:19Z

src/commands/pickFuncProcess.ts

+    const setPidByJsonOutputListener = vscode.window.onDidWriteTerminalData(async (event: vscode.TerminalDataWriteEvent) => {
+        const terminal = vscode.window.terminals.find(t => taskName === t.name);
+        if (event.terminal === terminal) {
+            if (event.data.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {


Using a hardcoded JSON fragment string for matching is fragile. JSON can have varying whitespace. Consider parsing the output as JSON or using a more robust pattern match that accounts for whitespace variations.

Co-authored-by: Copilot <[email protected]>

…ft/vscode-azurefunctions into nat/fileBasedPickProcess

Copilot

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

Copilot · 2025-10-30T22:54:35Z

src/funcCoreTools/funcHostTask.ts

+        const terminalEventReader = vscode.window.onDidStartTerminalShellExecution(async (terminalShellExecEvent) => {
+            /**
+             * NOTE: there is no reliable way to link a terminal to a task due to the name and PID not updating in real time,
+             * so just keep updating to the latest event since the func task and its dependencies run in the same
+             * terminal (the terminal that we want to output)
+             * New tasks will create new `terminalShellExecutionEvents`, so we don't need to worry about picking up output from other terminals
+             * */
+            latestTerminalShellExecutionEvent = terminalShellExecEvent;
+        });


The global latestTerminalShellExecutionEvent variable creates a race condition when multiple func tasks start concurrently. If two tasks start simultaneously, both will share the same terminalEventReader listener, but latestTerminalShellExecutionEvent may point to the wrong terminal. Consider storing the terminal event directly in the task object or using a Map keyed by task execution to avoid cross-contamination between concurrent tasks.

Copilot · 2025-10-30T22:54:35Z

src/funcCoreTools/funcHostTask.ts

+                terminalEventReader,
+                stream: latestTerminalShellExecutionEvent?.execution.read()


The stream may be assigned from an unrelated terminal due to the global latestTerminalShellExecutionEvent variable. Since the terminalEventReader listener updates this global asynchronously and there's no synchronization, the stream captured at line 116 might belong to a different task that fired its event between lines 104 and 116, especially under concurrent task execution.

Copilot · 2025-10-30T22:54:36Z

src/funcCoreTools/funcHostTask.ts

+let latestTerminalShellExecutionEvent: vscode.TerminalShellExecutionStartEvent | undefined;
 export function registerFuncHostTaskEvents(): void {
    registerEvent('azureFunctions.onDidStartTask', vscode.tasks.onDidStartTaskProcess, async (context: IActionContext, e: vscode.TaskProcessStartEvent) => {
+        const terminalEventReader = vscode.window.onDidStartTerminalShellExecution(async (terminalShellExecEvent) => {


A new terminal event listener is created for every task start event, but this listener captures events globally across all terminals. This creates unnecessary overhead with multiple event handlers for the same global events. Consider using a single global listener that filters by task context, or dispose of the listener once the relevant event is captured.

Copilot · 2025-10-30T22:54:36Z

src/commands/pickFuncProcess.ts

+    for await (const chunk of taskInfo.stream) {
+        if (chunk.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {
+            const matches = chunk.match(/"workerProcessId"\s*:\s*(\d+)/);
+            if (matches && matches.length > 1) {
+                return Number(matches[1]);
+            }
+        }
+    }
+    return;


The for await loop will consume the entire stream and never exit if the expected JSON output is not found, causing the function to hang indefinitely. The stream reading should have a timeout or break condition, and the loop at line 156 in startFuncTask should handle this case to avoid waiting forever.

Suggested change

for await (const chunk of taskInfo.stream) {

if (chunk.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {

const matches = chunk.match(/"workerProcessId"\s*:\s*(\d+)/);

if (matches && matches.length > 1) {

return Number(matches[1]);

}

}

}

return;

const TIMEOUT_MS = 10000; // 10 seconds

let timeoutHandle: NodeJS.Timeout;

return await Promise.race([

(async () => {

for await (const chunk of taskInfo.stream) {

if (chunk.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {

const matches = chunk.match(/"workerProcessId"\s*:\s*(\d+)/);

if (matches && matches.length > 1) {

clearTimeout(timeoutHandle);

return Number(matches[1]);

}

}

}

return undefined;

})(),

new Promise<number | undefined>(resolve => {

timeoutHandle = setTimeout(() => {

resolve(undefined);

}, TIMEOUT_MS);

})

]);

Copilot · 2025-10-30T22:54:36Z

src/commands/pickFuncProcess.ts

+        if (chunk.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {
+            const matches = chunk.match(/"workerProcessId"\s*:\s*(\d+)/);
+            if (matches && matches.length > 1) {
+                return Number(matches[1]);
+            }
+        }


The hardcoded JSON string fragment with specific formatting assumptions is brittle. JSON output may have varying whitespace, and this check will fail if the format changes slightly (e.g., no space after :). Consider parsing the chunk as JSON and checking the structure programmatically, or use a more flexible pattern that accommodates whitespace variations.

Suggested change

if (chunk.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {

const matches = chunk.match(/"workerProcessId"\s*:\s*(\d+)/);

if (matches && matches.length > 1) {

return Number(matches[1]);

}

}

let obj: unknown;

try {

obj = JSON.parse(chunk);

} catch {

continue; // Not valid JSON, skip this chunk

}

if (

typeof obj === 'object' &&

obj !== null &&

(obj as any).name === "dotnet-worker-startup" &&

typeof (obj as any).workerProcessId === "number"

) {

return (obj as any).workerProcessId;

}

Copilot · 2025-10-30T22:54:36Z

src/debug/FuncTaskProvider.ts

+        const args = (definition?.args || []) as string[];
+        if (args.length > 0) {
+            command = `${command} ${args.join(' ')}`;
+        }


Command arguments from task definitions are concatenated directly into shell commands without sanitization or escaping. If args contain shell metacharacters (e.g., ;, |, $(), backticks), this could lead to command injection. Consider using proper shell escaping or switching to an array-based execution approach where arguments are passed separately from the command.

src/commands/pickFuncProcess.ts

src/funcCoreTools/funcHostTask.ts

Implementation for debug-isolated flag and streaming func CLI output

6e5b61c

nturinski requested a review from a team as a code owner October 24, 2025 18:02

nturinski requested a review from Copilot October 24, 2025 18:05

Copilot AI reviewed Oct 24, 2025

View reviewed changes

nturinski and others added 7 commits October 24, 2025 11:09

Update src/utils/stream.ts

e9c255d

Co-authored-by: Copilot <[email protected]>

Address copilot feedback

067e04d

Merge branch 'nat/fileBasedPickProcess' of https://github.com/microso…

d046ac9

…ft/vscode-azurefunctions into nat/fileBasedPickProcess

Refactor to set up stream in funcHostTasks

606f130

Delete test snippet

44e8382

Add headerto stream file

9726543

Remove the done call

d4f3b56

nturinski requested a review from Copilot October 24, 2025 19:00

Copilot AI reviewed Oct 24, 2025

View reviewed changes

nturinski and others added 10 commits October 24, 2025 12:05

Update src/debug/FuncTaskProvider.ts

c7618c7

Co-authored-by: Copilot <[email protected]>

WIP waiting for VSCode insiders fix

b8dd0bf

Use onDidStartTerminalShellExecution API instead of proposed

d673a73

Remove proposed files

2dfd68d

Merge branch 'nat/fileBasedPickProcess' of https://github.com/microso…

5035c9a

…ft/vscode-azurefunctions into nat/fileBasedPickProcess

Add note

8a751c8

Remove unused async moniker

e5adbb9

Whoops, wrong async

6454ca8

Little bit of cleaning

544cd45

Remove unusued function helper

52780f7

nturinski requested a review from Copilot October 30, 2025 22:51

Copilot AI reviewed Oct 30, 2025

View reviewed changes

Last commit, I swears it

3dc0fc5

MicroFish91 reviewed Oct 31, 2025

View reviewed changes

src/commands/pickFuncProcess.ts Outdated Show resolved Hide resolved

src/funcCoreTools/funcHostTask.ts Outdated Show resolved Hide resolved

nturinski added 2 commits November 3, 2025 10:59

Move event handler, added note

e36604c

Rename function due to PR feedback

5bfbb42

		terminalEventReader,
		stream: latestTerminalShellExecutionEvent?.execution.read()

-        if (chunk.includes(`{ "name":"dotnet-worker-startup", "workerProcessId" :`)) {
-            const matches = chunk.match(/"workerProcessId"\s*:\s*(\d+)/);
-            if (matches && matches.length > 1) {
-                return Number(matches[1]);
-            }
-        }
+        let obj: unknown;
+        try {
+            obj = JSON.parse(chunk);
+        } catch {
+            continue; // Not valid JSON, skip this chunk
+        }
+        if (
+            typeof obj === 'object' &&
+            obj !== null &&
+            (obj as any).name === "dotnet-worker-startup" &&
+            typeof (obj as any).workerProcessId === "number"
+        ) {
+            return (obj as any).workerProcessId;
+        }

Implementation for debug-isolated flag and streaming func CLI output #4765

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nturinski commented Oct 24, 2025 •

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