Return evaluate result in DAP response body instead of writing to stdout by pdepetro · Pull Request #2027 · microsoft/debugpy

pdepetro · 2026-05-27T13:04:04Z

When a DAP client sends an evaluate request with context: "repl" and no frameId, debugpy forces the expression through the exec code path. Previously, if the expression could be compiled as an eval (e.g. 2 + 2), evaluate_expression would compute the result but write it to sys.stdout and return None. The caller in internal_evaluate_expression_json would then send back result="" in the response body. Clients that read the response body would get nothing, while the actual value was emitted as a DAP output event.

This changes evaluate_expression to return the computed result from the eval-within-exec path instead of printing it. The caller now captures that return value and includes it in the response body. Pure exec statements (e.g. x = 42) continue to return None and produce result="" as before.

VS Code is unaffected because it always provides a frameId, which routes through the normal eval path where results already go into the response body.

When a DAP client sends an `evaluate` request with `context: "repl"` and no `frameId`, debugpy forces the expression through the exec code path. Previously, if the expression could be compiled as an eval (e.g. `2 + 2`), `evaluate_expression` would compute the result but write it to `sys.stdout` and return `None`. The caller in `internal_evaluate_expression_json` would then send back `result=""` in the response body. Clients that read the response body would get nothing, while the actual value was emitted as a DAP output event. This changes `evaluate_expression` to return the computed result from the eval-within-exec path instead of printing it. The caller now captures that return value and includes it in the response body. Pure exec statements (e.g. `x = 42`) continue to return `None` and produce `result=""` as before. VS Code is unaffected because it always provides a `frameId`, which routes through the normal eval path where results already go into the response body.

rchiodo

It seems correct but I'm wondering why you wanted to change this? Is there a reason this is needed elsewhere?

Also what does VS code send if you're not stopped on a breakpoint and you try to eval something in the debug console?

rchiodo · 2026-05-27T16:44:13Z

/azp run

azure-pipelines · 2026-05-27T16:44:24Z

Azure Pipelines successfully started running 1 pipeline(s).

rchiodo · 2026-05-27T17:32:36Z

@@ -1239,12 +1239,16 @@ def __create_frame():



Copilot generated:
-1249

[unverified] The "%s" % (exec_result,) formatting at line 1249 now happens outside the try/except that catches exceptions from evaluate_expression. Previously, the equivalent "%s\n" % (result,) was inside evaluate_expression (at pydevd_vars.py:577), meaning any __str__ exception was caught by the caller's except (Exception, KeyboardInterrupt). Now an object with a broken __str__ will raise an unhandled exception at the response-formatting stage.

Suggested fix — move the formatting inside the try/except:

try: exec_result = pydevd_vars.evaluate_expression(py_db, frame, expression, is_exec=True) result = "%s" % (exec_result,) if exec_result is not None else "" except (Exception, KeyboardInterrupt): _evaluate_response_return_exception(py_db, request, *sys.exc_info()) return _evaluate_response(py_db, request, result=result)

The Advocate notes this uses the same %s as before, but the error-handling boundary has shifted — this is a new failure mode, not pre-existing.

[verified]

pdepetro · 2026-05-27T18:26:28Z

It seems correct but I'm wondering why you wanted to change this? Is there a reason this is needed elsewhere?

We have non-VS Code clients that are affected by this.

Also what does VS code send if you're not stopped on a breakpoint and you try to eval something in the debug console?

Evaluation without being stopped shows the behavior in VS Code as well:

Before the change:

11:17:17.422  --> evaluate
{"command":"evaluate","arguments":{"expression":"5+5","context":"repl"},"type":"request","seq":18}

11:17:17.466  <== output
{"body":{"category":"stdout","output":"10\n","source":{}},"event":"output","seq":44,"type":"event"}

after the change:

11:09:23.675  --> evaluate
{"command":"evaluate","arguments":{"expression":"5+5","context":"repl"},"type":"request","seq":18}

11:09:23.731  <-- evaluate
{"body":{"presentationHint":{},"result":"10","variablesReference":0},"command":"evaluate","request_seq":18,"seq":31,"success":true,"type":"response"}

My understanding is that the latter is the correct per the DAP spec, and matches how other debuggers respond.

rchiodo

Approved via Review Center.

rchiodo · 2026-05-27T19:01:02Z

Thanks Philip.

This MR contains the following updates: | Package | Type | Update | Change | OpenSSF | |---|---|---|---|---| | [debugpy](https://aka.ms/debugpy) ([source](https://github.com/microsoft/debugpy)) | dev | patch | `1.8.20` → `1.8.21` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/microsoft/debugpy/badge)](https://securityscorecards.dev/viewer/?uri=github.com/microsoft/debugpy) | | [numpy](https://github.com/numpy/numpy) ([changelog](https://numpy.org/doc/stable/release)) | dependencies | patch | `2.4.4` → `2.4.6` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/numpy/numpy/badge)](https://securityscorecards.dev/viewer/?uri=github.com/numpy/numpy) | | [pydantic-settings](https://github.com/pydantic/pydantic-settings) ([changelog](https://github.com/pydantic/pydantic-settings/releases)) | dependencies | patch | `2.14.0` → `2.14.2` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/pydantic/pydantic-settings/badge)](https://securityscorecards.dev/viewer/?uri=github.com/pydantic/pydantic-settings) | | [python-multipart](https://github.com/Kludex/python-multipart) ([changelog](https://github.com/Kludex/python-multipart/blob/master/CHANGELOG.md)) | dependencies | patch | `^0.0.22` → `^0.0.32` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/Kludex/python-multipart/badge)](https://securityscorecards.dev/viewer/?uri=github.com/Kludex/python-multipart) | | [types-requests](https://github.com/python/typeshed) ([changelog](https://github.com/typeshed-internal/stub_uploader/blob/main/data/changelogs/requests.md)) | dependencies | patch | `2.32.0.20240523` → `2.32.4.20260324` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/python/typeshed/badge)](https://securityscorecards.dev/viewer/?uri=github.com/python/typeshed) | --- ### Release Notes <details> <summary>microsoft/debugpy (debugpy)</summary> ### [`v1.8.21`](https://github.com/microsoft/debugpy/releases/tag/v1.8.21): debugpy v1.8.21 [Compare Source](microsoft/debugpy@v1.8.20...v1.8.21) Fixes for: - Return evaluate result in DAP response body instead of writing to stdout: [#2027](microsoft/debugpy#2027) - Prevent invalid `scopes` request from crashing debug session: [#2026](microsoft/debugpy#2026) - Skip uninitialized `__slots__` in variable resolver: [#2024](microsoft/debugpy#2024) - Handle `-c` arguments that are `bytes` instead of `str`: [#2021](microsoft/debugpy#2021) - Fix evaluation of variables from chained exception frames: [#2018](microsoft/debugpy#2018) - `ContinueRequest` with a specific `threadId` no longer resumes all threads (in-process adapter): [#2012](microsoft/debugpy#2012) - Avoid strong reference to exceptions during unwind: [#2008](microsoft/debugpy#2008) - Show error message on evaluate failures in the hover context: [#2006](microsoft/debugpy#2006) - Display `dlerror` output when `dlopen` fails: [#2000](microsoft/debugpy#2000) - Replace removed `pkgutil.get_loader` with `importlib.util.find_spec` in `get_fullname`: [#1998](microsoft/debugpy#1998) Enhancements: - Add option to ignore all system exit codes: [#2017](microsoft/debugpy#2017) - Pull changes from pydevd up to March 2026: [#2010](microsoft/debugpy#2010) Infrastructure work: - Suppress Flawfinder false positives on Cython memcpy / read-loop iterators (TSA [#2816216](https://github.com/microsoft/debugpy/issues/2816216), [#2816217](https://github.com/microsoft/debugpy/issues/2816217), [#2816218](https://github.com/microsoft/debugpy/issues/2816218), [#2816219](https://github.com/microsoft/debugpy/issues/2816219), [#2816220](https://github.com/microsoft/debugpy/issues/2816220)): [#2028](microsoft/debugpy#2028), [#2029](microsoft/debugpy#2029), [#2030](microsoft/debugpy#2030), [#2031](microsoft/debugpy#2031), [#2032](microsoft/debugpy#2032) Thanks to [@maxbachmann](https://github.com/maxbachmann), [@mfussenegger](https://github.com/mfussenegger), and [@sambrightman](https://github.com/sambrightman) for the commits. </details> <details> <summary>numpy/numpy (numpy)</summary> ### [`v2.4.6`](https://github.com/numpy/numpy/releases/tag/v2.4.6): (May 18, 2026) [Compare Source](numpy/numpy@v2.4.5...v2.4.6) ### NumPy 2.4.6 Release Notes NumPy 2.4.6 is a quick release that fixes a regression discovered in the 2.4.5 release. This release supports Python versions 3.11-3.14 #### Contributors A total of 4 people contributed to this release. People with a "+" by their names contributed a patch for the first time. - !EarlMilktea - Charles Harris - Sebastian Berg - Warren Weckesser #### Pull requests merged A total of 4 pull requests were merged for this release. - [#31444](numpy/numpy#31444): MAINT: Prepare 2.4.x for further development - [#31453](numpy/numpy#31453): BUG: Fix regression in `arr.conj()` - [#31459](numpy/numpy#31459): BUG: `np.linalg.svd(..., hermitian=True)` returns non-unitary... - [#31460](numpy/numpy#31460): BUG: Don't call INCREF/DECREF on descr in NpyStringAcquireAllocator... ### [`v2.4.5`](https://github.com/numpy/numpy/releases/tag/v2.4.5): (May 15, 2026) [Compare Source](numpy/numpy@v2.4.4...v2.4.5) ### NumPy 2.4.5 Release Notes NumPy 2.4.5 is a patch release that fixes bugs discovered after the 2.4.4 release, has some typing improvements, and maintains infrastructure. This release supports Python versions 3.11-3.14 #### Contributors A total of 17 people contributed to this release. People with a "+" by their names contributed a patch for the first time. - Aleksei Nikiforov - Anarion Zuo + - Ankit Ahlawat - Breno Favaretto + - Charles Harris - Igor Krivenko + - Ijtihed Kilani + - Joren Hammudoglu - Maarten Baert + - Matti Picus - Nathan Goldbaum - Praneeth Kodumagulla + - Ralf Gommers - RoomWithOutRoof + - Sebastian Berg - Warren Weckesser - div + #### Pull requests merged A total of 28 pull requests were merged for this release. - [#31093](numpy/numpy#31093): MAINT: Prepare 2.4.x for further development - [#31182](numpy/numpy#31182): TYP: fix `np.shape` assignability issue for python lists ([#31171](numpy/numpy#31171)) - [#31197](numpy/numpy#31197): ENH: Return rank 0 for empty matrices in matrix\_rank ([#30422](numpy/numpy#30422)) - [#31198](numpy/numpy#31198): CI/BUG: add native jobs for s390x, fix bug in `pack_inner`... - [#31199](numpy/numpy#31199): BUG: f2py map complex\_long\_double to NPY\_CLONGDOUBLE - [#31205](numpy/numpy#31205): MAINT: f2py: Stop setting re.\_MAXCACHE to 50. - [#31206](numpy/numpy#31206): BUG: fix heap buffer overflow in timedelta to string casts - [#31207](numpy/numpy#31207): MAINT: Rename ppc64le and s390x workflow ([#31121](numpy/numpy#31121)) - [#31208](numpy/numpy#31208): BUG: Fix matvec/vecmat in-place aliasing (out=input produces... - [#31209](numpy/numpy#31209): TYP: `tile`: accept numpy scalars and arrays as second argument... - [#31211](numpy/numpy#31211): DEP: Undo deprecation for np.dtype() signature used by old pickles... - [#31212](numpy/numpy#31212): REV: Manual revert of float16 svml use ([#31178](numpy/numpy#31178)) - [#31222](numpy/numpy#31222): TYP: `ix_` fix for boolean and non-1d input ([#31218](numpy/numpy#31218)) - [#31329](numpy/numpy#31329): BUG: incorrect temp elision for new-style (NEP 43) user-defined... - [#31330](numpy/numpy#31330): TYP: fix sliding\_window\_view axis parameter typing - [#31335](numpy/numpy#31335): BUG: Prevent deadlock due to downstream importing NumPy in dlopen... - [#31336](numpy/numpy#31336): BUG: Fix segfault in nditer.multi\_index when \_\_getitem\_\_ raises... - [#31338](numpy/numpy#31338): TYP: Fix ruff lint error - [#31357](numpy/numpy#31357): BUG: fix memory leak in np.zeros when fill-zero loop raises ([#31320](numpy/numpy#31320)) - [#31358](numpy/numpy#31358): BUG: np.einsum() fails with a 0-dimensional out argument and... - [#31379](numpy/numpy#31379): BUG: Fix signed overflow issue in npy\_gcd for INT\_MIN on s390x... - [#31383](numpy/numpy#31383): CI: remove Cirrus CI FreeBSD job ([#31380](numpy/numpy#31380)) - [#31390](numpy/numpy#31390): BUILD: newer MKL uses so.3 - [#31391](numpy/numpy#31391): BLD/MAINT: improve support for Intel LLVM compilers - [#31401](numpy/numpy#31401): BUG: Avoid UB in [safe]()\[add,sub,mul] helpers ([#31396](numpy/numpy#31396)) - [#31402](numpy/numpy#31402): BUG: exclude \_\_pycache\_\_ directories from wheels ([#31397](numpy/numpy#31397)) - [#31404](numpy/numpy#31404): TYP: `_NestedSequence` type parameter default to work around... - [#31426](numpy/numpy#31426): TYP: Fix `DTypeLike` runtime type-checker support ([#31425](numpy/numpy#31425)) </details> <details> <summary>pydantic/pydantic-settings (pydantic-settings)</summary> ### [`v2.14.2`](https://github.com/pydantic/pydantic-settings/releases/tag/v2.14.2) [Compare Source](pydantic/pydantic-settings@v2.14.1...v2.14.2) #### What's Changed This is a security patch release. - Prevent `NestedSecretsSettingsSource` from following symlinks outside `secrets_dir` by [@hramezani](https://github.com/hramezani) in [#889](pydantic/pydantic-settings#889) - Prepare release 2.14.2 by [@hramezani](https://github.com/hramezani) in [#890](pydantic/pydantic-settings#890) ##### Security Fixes [GHSA-4xgf-cpjx-pc3j](GHSA-4xgf-cpjx-pc3j): `NestedSecretsSettingsSource` with `secrets_nested_subdir=True` could follow a symbolic link inside `secrets_dir` pointing outside it, reading out-of-tree files into settings values and bypassing the `secrets_dir_max_size` cap. Affected versions: `>= 2.12.0, < 2.14.2`. **Full Changelog**: <pydantic/pydantic-settings@v2.14.1...v2.14.2> ### [`v2.14.1`](https://github.com/pydantic/pydantic-settings/releases/tag/v2.14.1) [Compare Source](pydantic/pydantic-settings@v2.14.0...v2.14.1) #### What's Changed - Bump the python-packages group with 4 updates by [@dependabot](https://github.com/dependabot)\[bot] in [#850](pydantic/pydantic-settings#850) - Bump the python-packages group with 5 updates by [@dependabot](https://github.com/dependabot)\[bot] in [#854](pydantic/pydantic-settings#854) - Bump the github-actions group with 3 updates by [@dependabot](https://github.com/dependabot)\[bot] in [#853](pydantic/pydantic-settings#853) - Bump the python-packages group with 2 updates by [@dependabot](https://github.com/dependabot)\[bot] in [#856](pydantic/pydantic-settings#856) - Fix field named `cls` conflicting with classmethod parameter by [@hramezani](https://github.com/hramezani) in [#858](pydantic/pydantic-settings#858) - Prepare release 2.14.1 by [@hramezani](https://github.com/hramezani) in [#859](pydantic/pydantic-settings#859) **Full Changelog**: <pydantic/pydantic-settings@v2.14.0...v2.14.1> </details> <details> <summary>Kludex/python-multipart (python-multipart)</summary> ### [`v0.0.32`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0032-2026-06-04) [Compare Source](Kludex/python-multipart@0.0.31...0.0.32) - Speed up partial-boundary scanning for CR/LF-dense part data [#300](Kludex/python-multipart#300). ### [`v0.0.31`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0031-2026-06-04) [Compare Source](Kludex/python-multipart@0.0.30...0.0.31) - Speed up multipart header parsing and callback dispatch [#295](Kludex/python-multipart#295). - Bound header field name size before validating [#296](Kludex/python-multipart#296). - Validate `Content-Length` is non-negative in `parse_form` [#297](Kludex/python-multipart#297). ### [`v0.0.30`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0030-2026-05-31) [Compare Source](Kludex/python-multipart@0.0.29...0.0.30) - Parse `application/x-www-form-urlencoded` bodies per the WHATWG URL standard, treating only `&` as a field separator [#290](Kludex/python-multipart#290). - Ignore RFC 2231/5987 extended parameters (`name*`, `filename*`) in `parse_options_header`, keeping the plain parameter authoritative per [RFC 7578 §4.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) [#291](Kludex/python-multipart#291). ### [`v0.0.29`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0029-2026-05-17) [Compare Source](Kludex/python-multipart@0.0.28...0.0.29) - Handle malformed RFC 2231 continuations in `parse_options_header` [#270](Kludex/python-multipart#270). ### [`v0.0.28`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0028-2026-05-10) [Compare Source](Kludex/python-multipart@0.0.27...0.0.28) - Speed up partial-boundary tail scan via `bytes.find` [#281](Kludex/python-multipart#281). - Cap multipart boundary length at 256 bytes [#282](Kludex/python-multipart#282). ### [`v0.0.27`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0027-2026-04-27) [Compare Source](Kludex/python-multipart@0.0.26...0.0.27) - Add multipart header limits [#267](Kludex/python-multipart#267). - Pass parse offsets via constructors [#268](Kludex/python-multipart#268). ### [`v0.0.26`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0026-2026-04-10) [Compare Source](Kludex/python-multipart@0.0.25...0.0.26) - Skip preamble before the first multipart boundary more efficiently [#262](Kludex/python-multipart#262). - Silently discard epilogue data after the closing multipart boundary [#259](Kludex/python-multipart#259). ### [`v0.0.25`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0025-2026-04-10) [Compare Source](Kludex/python-multipart@0.0.24...0.0.25) - Add MIME content type info to `File` [#143](Kludex/python-multipart#143). - Handle CTE values case-insensitively [#258](Kludex/python-multipart#258). - Remove custom `FormParser` classes [#257](Kludex/python-multipart#257). - Add `UPLOAD_DELETE_TMP` to `FormParser` config [#254](Kludex/python-multipart#254). - Emit `field_end` for trailing bare field names on finalize [#230](Kludex/python-multipart#230). - Handle multipart headers case-insensitively [#252](Kludex/python-multipart#252). - Apply Apache-2.0 properly [#247](Kludex/python-multipart#247). ### [`v0.0.24`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0024-2026-04-05) [Compare Source](Kludex/python-multipart@0.0.23...0.0.24) - Validate `chunk_size` in `parse_form()` [#244](Kludex/python-multipart#244). ### [`v0.0.23`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0023-2026-04-05) [Compare Source](Kludex/python-multipart@0.0.22...0.0.23) - Remove unused `trust_x_headers` parameter and `X-File-Name` fallback [#196](Kludex/python-multipart#196). - Return processed length from `QuerystringParser._internal_write` [#229](Kludex/python-multipart#229). - Cleanup metadata dunders from `__init__.py` [#227](Kludex/python-multipart#227). </details> --- - [ ] If you want to rebase/retry this MR, check this box --- This MR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).  See merge request swiss-armed-forces/cyber-command/cea/loom!460 Co-authored-by: Loom MR Pipeline Trigger <group_103951964_bot_9504bb8dead6d4e406ad817a607f24be@noreply.gitlab.com> Co-authored-by: shrewd-laidback palace <shrewd-laidback-palace-736-c41-2c1-e464fc974@swiss-armed-forces-open-source.ch>

pdepetro requested a review from a team as a code owner May 27, 2026 13:04

rchiodo reviewed May 27, 2026

View reviewed changes

rchiodo approved these changes May 27, 2026

View reviewed changes

rchiodo merged commit 12bd4fe into microsoft:main May 27, 2026
24 of 27 checks passed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Return evaluate result in DAP response body instead of writing to stdout#2027

Return evaluate result in DAP response body instead of writing to stdout#2027
rchiodo merged 1 commit into
microsoft:mainfrom
pdepetro:main

pdepetro commented May 27, 2026

Uh oh!

rchiodo left a comment

Uh oh!

rchiodo commented May 27, 2026

Uh oh!

azure-pipelines Bot commented May 27, 2026

Uh oh!

rchiodo May 27, 2026

Uh oh!

pdepetro commented May 27, 2026

Uh oh!

rchiodo left a comment

Uh oh!

rchiodo commented May 27, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

pdepetro commented May 27, 2026

Uh oh!

rchiodo left a comment

Choose a reason for hiding this comment

Uh oh!

rchiodo commented May 27, 2026

Uh oh!

azure-pipelines Bot commented May 27, 2026

Uh oh!

rchiodo May 27, 2026

Choose a reason for hiding this comment

Uh oh!

pdepetro commented May 27, 2026

Uh oh!

rchiodo left a comment

Choose a reason for hiding this comment

Uh oh!

rchiodo commented May 27, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants