Support creating YAML config files via `devproxy config new` (extension or `--format`) by Copilot · Pull Request #1559 · dotnet/dev-proxy

Copilot · 2026-02-25T14:05:08Z

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This section details on the original issue you should resolve

<issue_title>Support creating YAML config files via devproxy config new</issue_title>
<issue_description>## Summary

devproxy config new currently defaults to creating a devproxyrc.json file and only generates JSON configs. With YAML config support being added (#1491), the CLI should also support creating YAML-based configuration files.

Expected behavior

devproxy config new devproxyrc.yaml should create a valid YAML config file

The format should be inferred from the file extension (.yaml/.yml = YAML, .json/.jsonc = JSON)

The default should remain devproxyrc.json for backward compatibility

Current behavior

devproxy config new only generates JSON configs regardless of the filename extension. It downloads a JSON snippet from the snippets URL and writes it as-is.

Additional context

Discovered while testing PR #1491 (YAML config support).</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes Support creating YAML config files via devproxy config new #1558

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

Co-authored-by: garrytrinder <11563347+garrytrinder@users.noreply.github.com>

waldekmastykarz · 2026-02-25T14:52:38Z

@garrytrinder should we also have a --format json|yaml option in case you want to use the default name but just specify the format? Might be more discoverable than just the file name

garrytrinder · 2026-02-26T14:08:42Z

@copilot fix the merge conflicts

garrytrinder · 2026-02-26T14:24:07Z

@garrytrinder should we also have a --format json|yaml option in case you want to use the default name but just specify the format? Might be more discoverable than just the file name

Good idea.

@copilot add a new optional option to the command that can determine the format to be used without specifying the filename

Co-authored-by: garrytrinder <11563347+garrytrinder@users.noreply.github.com>

Copilot · 2026-02-26T14:30:51Z

@garrytrinder should we also have a --format json|yaml option in case you want to use the default name but just specify the format? Might be more discoverable than just the file name

Good idea....

Implemented in e24a670. devproxy config new now supports an optional --format <Json|Yaml> option, and when used without a filename it defaults to devproxyrc.yaml for YAML (otherwise devproxyrc.json).

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

aka.ms
- Triggering command: /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy config new /tmp/devproxy-config-test/from-extension.yaml --output json (dns block)
- Triggering command: /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy config new --format yaml /tmp/devproxy-config-test/from-format-default-name-placeholder --output json (dns block)
- Triggering command: /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy config new --format yaml --output json (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Copilot

Pull request overview

This PR extends the devproxy config new command to support creating YAML configuration files in addition to the existing JSON format.

Changes:

Added format detection based on file extension (.yaml/.yml for YAML, .json/.jsonc for JSON)
Introduced a --format option to explicitly specify the output format (json or yaml)
Implemented JSON-to-YAML conversion using System.Text.Json and YamlDotNet

DevProxy/Commands/ConfigCommand.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>

Copilot · 2026-02-27T08:16:54Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

aka.ms
- Triggering command: /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy config new --format yaml --help (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

waldekmastykarz

LGTM. Build passes, review feedback (JsonDocument disposal, UInt64 precision) has been addressed. The format inference from file extension and the --format option work correctly.

Minor nit: there's a missing blank line between ConvertJsonElement and ResolveConfigFile (around line 617-618), but not a blocker.

Retracting approval: unable to verify e2e because the v2.2.0 snippets URL is not live yet. The JSON-to-YAML conversion logic was verified in isolation and works correctly. Pending full e2e test once the snippets URL is published.

waldekmastykarz · 2026-02-28T09:38:29Z

Code review looks the JSON-to-YAML conversion logic works correctly in isolation (build passes, disposal and precision feedback addressed). However, we cannot verify e2e because config new depends on the snippets URL (https://aka.ms/devproxy/snippets/v2.2.0) which is not live yet (returns HTML instead of JSON). This affects main as well, not just this PR.good

Blocking on: snippets URL for v2.2.0 being published. Once it is live, we can do a full e2e test and re-approve.

garrytrinder · 2026-03-02T10:23:31Z

Converted to draft as we need to update the toolkit with YAML snippets and create new aka.ms links for JSON and YAML snippets for v2.2.0

waldekmastykarz · 2026-03-02T11:01:31Z

@garrytrinder as we're fixing this, let's add an empty line in the code, in the place mentioned earlier in comments

garrytrinder · 2026-03-03T15:25:34Z

aka.ms links for v2.2.0 snippets are now live

@copilot

Co-authored-by: garrytrinder <11563347+garrytrinder@users.noreply.github.com>

Copilot · 2026-03-03T15:29:47Z

@garrytrinder as we're fixing this, let's add an empty line in the code, in the place mentioned earlier in comments

Done in 0d9ecd2. Added the missing blank line between ConvertJsonElement and ResolveConfigFile in ConfigCommand.cs. No UI changes (CLI-only change).

aka.ms links for v2.2.0 snippets are now live

JSON: https://aka.ms/devproxy/snippets/v2.2.0/json
...

I ran a targeted config new smoke test after the latest updates; build is passing, and the remaining e2e fetch check is blocked in this sandbox by outbound connectivity to aka.ms (SocketException: Resource temporarily unavailable). The code changes for YAML format support and follow-up review nits are in 0d9ecd2/f01c612/aabf572. No UI changes (CLI-only change).

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

aka.ms
- Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
- Triggering command: /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy config new smoke.json (dns block)
- Triggering command: /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy /home/REDACTED/work/dev-proxy/dev-proxy/DevProxy/bin/Debug/net10.0/devproxy config new --format yaml smoke.yaml (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Download snippets from /json or /yaml endpoint instead of a single URL. Removes client-side JSON-to-YAML conversion since YAML snippets are now served natively. Closes #1559

garrytrinder

Tested config new command with format-specific snippets URLs. All scenarios pass: default JSON, --format yaml, --format json, extension-based inference, format override, and overwrite protection. LGTM.

Initial plan

c473bfb

Copilot AI assigned Copilot and garrytrinder Feb 25, 2026

Copilot started work on behalf of garrytrinder February 25, 2026 14:05 View session

Support creating YAML config files via devproxy config new

46095a4

Co-authored-by: garrytrinder <11563347+garrytrinder@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Support creating YAML config files via devproxy config new~~ Support creating YAML config files via devproxy config new Feb 25, 2026

Copilot finished work on behalf of garrytrinder February 25, 2026 14:09

Merge branch 'main' into copilot/add-yaml-config-support-again

4e4c21c

Merge branch 'main' into copilot/add-yaml-config-support-again

4ba5a03

Copilot started work on behalf of garrytrinder February 26, 2026 14:08 View session

Copilot finished work on behalf of garrytrinder February 26, 2026 14:11

Merge branch 'main' into copilot/add-yaml-config-support-again

4dfacac

Copilot started work on behalf of garrytrinder February 26, 2026 14:24 View session

Add optional --format to config new command

e24a670

Co-authored-by: garrytrinder <11563347+garrytrinder@users.noreply.github.com>

Copilot AI changed the title ~~Support creating YAML config files via devproxy config new~~ Support creating YAML config files via devproxy config new (extension or --format) Feb 26, 2026

Copilot finished work on behalf of garrytrinder February 26, 2026 14:31

garrytrinder marked this pull request as ready for review February 26, 2026 14:56

garrytrinder requested a review from a team as a code owner February 26, 2026 14:56

Copilot AI review requested due to automatic review settings February 26, 2026 14:56

Copilot AI reviewed Feb 26, 2026

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DevProxy/Commands/ConfigCommand.cs Outdated Show resolved Hide resolved

DevProxy/Commands/ConfigCommand.cs Outdated Show resolved Hide resolved

garrytrinder mentioned this pull request Feb 26, 2026

YAML snippets dev-proxy-tools/toolkit#344

Closed

Copilot AI mentioned this pull request Feb 26, 2026

Add YAML snippets for Dev Proxy config files dev-proxy-tools/toolkit#345

Merged

6 tasks

Update DevProxy/Commands/ConfigCommand.cs

aabf572

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot started work on behalf of waldekmastykarz February 27, 2026 08:13 View session

waldekmastykarz and others added 2 commits February 27, 2026 09:13

Merge branch 'main' into copilot/add-yaml-config-support-again

9257fe7

Dispose JsonDocument in YAML conversion helper

f01c612

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>

Copilot finished work on behalf of waldekmastykarz February 27, 2026 08:17

Merge branch 'main' into copilot/add-yaml-config-support-again

3d4648d

waldekmastykarz previously approved these changes Feb 28, 2026

View reviewed changes

garrytrinder marked this pull request as draft March 2, 2026 10:22

Merge branch 'main' into copilot/add-yaml-config-support-again

c7f4d80

Merge branch 'main' into copilot/add-yaml-config-support-again

a07fe72

Copilot started work on behalf of garrytrinder March 3, 2026 15:25 View session

Add missing blank line between ConfigCommand helper methods

0d9ecd2

Co-authored-by: garrytrinder <11563347+garrytrinder@users.noreply.github.com>

Copilot finished work on behalf of garrytrinder March 3, 2026 15:30

waldekmastykarz and others added 2 commits March 4, 2026 08:39

Merge branch 'main' into copilot/add-yaml-config-support-again

af50ee8

Use format-specific snippets URLs for config new command

23c3cf5

Download snippets from /json or /yaml endpoint instead of a single URL. Removes client-side JSON-to-YAML conversion since YAML snippets are now served natively. Closes #1559

garrytrinder approved these changes Mar 4, 2026

View reviewed changes

garrytrinder marked this pull request as ready for review March 4, 2026 09:41

waldekmastykarz approved these changes Mar 4, 2026

View reviewed changes

waldekmastykarz merged commit a5bead6 into main Mar 4, 2026
4 checks passed

waldekmastykarz deleted the copilot/add-yaml-config-support-again branch March 4, 2026 09:51

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Copilot AI commented Feb 27, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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