Debug adapter protocol client implementation and bridge mode for IDE by danegsta · Pull Request #78 · microsoft/dcp

David Negstad (danegsta) · 2026-02-11T21:40:53Z

Implements a debug adapter protocol (DAP) client and support for a new debug adapter protocol bridge based IDE debugging mode.

Opening this as a draft because it's both very large and I want to spend more time on the Aspire side of the bridge to make sure things are fully stable before I mark it ready for review.

…t trigger state changes are run

Karol Zadora-Przylecki (karolz-ms)

Big PR, so will be sending my feedback in "chunks" -- hope this helps!

(this is the first one)

Karol Zadora-Przylecki (karolz-ms) · 2026-02-20T22:32:10Z

+
+	l.closed = true
+
+	closeErr := l.listener.Close()


Release lock before calling Close()

I implemented the retained error, which means we have to hold the lock until we've actually resolved the error value.

Karol Zadora-Przylecki (karolz-ms)

Initial PR review part 2

Karol Zadora-Przylecki (karolz-ms) · 2026-02-21T01:39:27Z

+ t.Parallel()
+ rootDir := shortTempDir(t)
+
+ listener, createErr := NewSecureSocketListener(rootDir, "afc-")


The test that we should really have is the following:
Create a new socket listener and do Accept() (blocks).
Launch 10 different goroutines and make them race to call Close() on the listener.
Verify that Accept() returns with errClosed (a distinct error that allows the caller to differentiate between "somebody closed be because it is time to shut down" vs another, unexpected error).
Verify that all calls to Close() returned with no error.

Karol Zadora-Przylecki (karolz-ms)

Comments on the DAP implmentation, part 1

Karol Zadora-Przylecki (karolz-ms) · 2026-02-23T23:34:30Z

+	// If the adapter did not send a TerminatedEvent, synthesize one for the IDE.
+	// Also send an error OutputEvent if we exited due to a transport error.
+	terminated := b.terminatedEventSeen.Load()
+
+	if !terminated {
+ if loopErr != nil && !errors.Is(loopErr, io.EOF) && !errors.Is(loopErr, context.Canceled) {
+ b.sendErrorToIDE(fmt.Sprintf("Debug session ended unexpectedly: %v", loopErr))
+ } else {
+ b.sendTerminatedToIDE()
+ }
+	}


I would prefer if the forwardAdapterToIDE goroutine was "told" to do this (e.g. via a separate channel). This eliminates the race between the two goroutines with regards to reading/writing terminatedEventSeen and also ensures that a single goroutine is writing to the IDE socket.
To be clear, having multiple goroutines writing to the same socket is not strictly forbidden, but adds another degree of asynchrony.

Karol Zadora-Przylecki (karolz-ms) · 2026-02-23T23:53:23Z

+func (b *DapBridge) handleOutputEvent(event *dap.OutputEvent) {
+	// Only capture output if runInTerminal wasn't used
+	// (if runInTerminal was used, we capture directly from the process)
+	if !b.runInTerminalUsed.Load() && b.config.OutputHandler != nil {


Seems like runInTerminalUsed is only used by the adapter --> IDE goroutine, so it can probably be just a regular bool flag.

I'm mostly leaving this as an atomic bool out of an abundance of caution.

Karol Zadora-Przylecki (karolz-ms)

DAP bridge review, part 2

Karol Zadora-Przylecki (karolz-ms) · 2026-02-26T19:42:35Z

+type HandshakeReader struct {
+	conn net.Conn
+}


Is there a particular reason to define HandshakeReader this way as oppose do
Suggested change
typeHandshakeReaderstruct {
conn net.Conn
}
typeHandshakeReader net.Conn

No specific reason

Karol Zadora-Przylecki (karolz-ms) · 2026-02-26T19:44:57Z

+type HandshakeWriter struct {
+	conn net.Conn
+}


Same question as for HandshakeReader
Suggested change
typeHandshakeWriterstruct {
conn net.Conn
}
typeHandshakeWriter net.Conn

Karol Zadora-Przylecki (karolz-ms)

Finished initial review. This is a fantastic and impressive change!

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

… re-uses an existing adapter session

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

David Negstad (danegsta) added 8 commits January 30, 2026 12:39

Add initial DAP proxy implementation
41ce1ee

Add an end-to-end test that drives a delve debugger instance using DAP
78205e1

Initial gRPC side-channel
093873f

Add additional integration tests
ec15d11

Ensure events are sent to keep IDE up to date when virtual events tha…
45aee07
…t trigger state changes are run

Support additional debug adapter connection modes
918ef7f

Update to use our process and context aware read helpers
527a6b2

Cleanup and prepare DAP support to be ready for PR
be6fe42

David Negstad (danegsta) requested a review from Karol Zadora-Przylecki (karolz-ms)February 11, 2026 21:40

David Negstad (danegsta) added 8 commits February 11, 2026 16:25

Ensure debug adapters launch with necessary environment
48af052

Improvements to debug adapter tests
4af1824

Fix test on Windows
53b2c31

Added better error message in test
66c3576

Ensure proper goargs for all test binaries
50b783c

Go environment handling in dlv test
f03ab74

Ensure test doesn't force x64
ec06ea7

Simplify to a single markdown on the new feature
a4e781d

Karol Zadora-Przylecki (karolz-ms) reviewed Feb 20, 2026
View reviewed changes

Karol Zadora-Przylecki (karolz-ms) reviewed Feb 21, 2026
View reviewed changes

Karol Zadora-Przylecki (karolz-ms) reviewed Feb 23, 2026
View reviewed changes

David Negstad (danegsta) added 2 commits February 25, 2026 18:57

Merge remote-tracking branch 'origin/main' into dev/danegsta/dap
38357dc

Updates for PR feedback
5d631f7

Karol Zadora-Przylecki (karolz-ms) reviewed Feb 26, 2026
View reviewed changes

David Negstad (danegsta) added 2 commits February 26, 2026 14:29

Rename NewProcessHandle to NewHandle
bb11ec6

Remove usage of secure from user-only unix socket helper names
3ba349e

Karol Zadora-Przylecki (karolz-ms) reviewed Feb 26, 2026
View reviewed changes

Comment threadinternal/dap/transport.go Outdated
Comment threadinternal/dap/transport.go
Comment threadMakefile Outdated

Karol Zadora-Przylecki (karolz-ms) reviewed Feb 27, 2026
View reviewed changes

Comment threadinternal/dap/transport.go Outdated

David Negstad (danegsta) added 3 commits March 6, 2026 20:53

More updates for PR comments
9bb186e

Fix race condition
43dd503

More PR updates, fix failing test
e102589

David Negstad (danegsta)and others added 8 commits March 6, 2026 22:34

Remove unnecessary test
c4bae1b

Update to send terminal message via queue
da245c2

Merge origin/main into branch
566fccd
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Refine DAP bridge manager concurrency
e1893fc
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Updates to support additional scenarios such as JS debug adapter that…
e225b08
… re-uses an existing adapter session

Merge origin/main into dev/danegsta/dap
46fe1f0
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge origin/main into dev/danegsta/dap
4164a9c
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Regenerate NOTICE
2d493f4
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

-typeHandshakeReaderstruct {
-	conn net.Conn
-}
+typeHandshakeReader net.Conn

-typeHandshakeWriterstruct {
-	conn net.Conn
-}
+typeHandshakeWriter net.Conn

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David Negstad (danegsta) commented Feb 11, 2026

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