inject x-defang-llm on model services, convert fixup snapshots to YAML

[jordanstephens]

Summary

• Sets x-defang-llm: true on services derived from the compose models: top-level block (in addition to the existing x-defang-llm extension path)
• Converts TestFixup snapshots from JSON to YAML so that compose extensions (x-defang-llm, etc.) are visible in snapshots — compose-go tags Extensions as json:"-", making all extension changes invisible to the previous JSON-based snapshots

Blocks DefangLabs/samples#647

Test plan

• TestFixup passes and the regenerated snapshots show x-defang-llm: true on model services
• Verify x-defang-llm appears correctly on services generated from models: entries in a real compose file

Summary by CodeRabbit

• New Features

  • Compose fixup output now uses YAML across fixtures and comparisons, matching the expected compose format more closely.
  • Services generated from model-based configurations now include the appropriate x-defang-llm metadata.

• Bug Fixes

  • Removed unnecessary null fields from generated compose output, producing cleaner and more consistent results.
  • Preserved service settings such as images, builds, ports, networks, and environment values while improving output formatting.

[coderabbitai]

📝 Walkthrough

Walkthrough

Compose fixup generation now serializes fixtures as YAML, and generated model services receive x-defang-llm. The fixture corpus was rewritten from JSON-like output to YAML across basic service cases, orchestration cases, and extension-heavy cases.

Changes

Compose fixup YAML migration

Layer / File(s)	Summary
YAML serializer and model tagging src/go.mod, src/pkg/cli/compose/fixup.go, src/pkg/cli/compose/fixup_test.go	FixupServices now adds x-defang-llm to generated model services, and the fixup test marshals fixture comparisons as YAML.
Small fixture rewrites src/testdata/Fancy-Proj_Dir/compose.yaml.fixup, src/testdata/empty/compose.yaml.fixup, src/testdata/noprojname/compose.yaml.fixup, src/testdata/alttestproj/compose.yaml.fixup, src/testdata/base-image/compose.yaml.fixup, src/testdata/build-image/compose.yaml.fixup, src/testdata/build/compose.yaml.fixup, src/testdata/bun-in-compose/compose.yaml.fixup, src/testdata/bun-in-dockerfile/compose.yaml.fixup, src/testdata/compose-go-warn/compose.yaml.fixup, src/testdata/configdetection/compose.yaml.fixup, src/testdata/configoverride/compose.yaml.fixup, src/testdata/debugproj/compose.yaml.fixup, src/testdata/longname/compose.yaml.fixup, src/testdata/platforms/compose.yaml.fixup, src/testdata/provider/compose.yaml.fixup, src/testdata/secretname/compose.yaml.fixup, src/testdata/toomany/compose.yaml.fixup, src/testdata/toomany/docker-compose.yml.fixup	Several small fixture cases were rewritten to YAML while keeping images, builds, networks, and other simple service fields, and dropping explicit command/entrypoint nulls.
Multi-service fixture rewrites src/testdata/ambiguous-strings/compose.yaml.fixup, src/testdata/build/compose.yaml.fixup, src/testdata/emptyenv/compose.yaml.fixup, src/testdata/extends/compose.yaml.fixup, src/testdata/interpolate/compose.yaml.fixup, src/testdata/profiles/compose.yaml.fixup, src/testdata/railpack/compose.yaml.fixup, src/testdata/testproj/compose.yaml.fixup	Multi-service fixtures for builds, extends, environments, profiles, and service definitions were rewritten to YAML while preserving the same service keys and values.
Ports, networks, and lifecycle fixtures src/testdata/dependson/compose.yaml.fixup, src/testdata/dockerfile-validation-errors/compose.yaml.fixup, src/testdata/healthcheck/compose.yaml.fixup, src/testdata/heroku/compose.yaml.fixup, src/testdata/networks/compose.yaml.fixup, src/testdata/ports/compose.yaml.fixup, src/testdata/postgres/compose.yaml.fixup, src/testdata/replicas/compose.yaml.fixup, src/testdata/sanity/compose.yaml.fixup, src/testdata/fixupenv/compose.yaml.fixup, src/testdata/gpu/compose.yaml.fixup	Fixtures covering depends_on, ports, healthchecks, networks, replicas, and other orchestration settings were rewritten to YAML with the same retained values.
Extension fixtures src/testdata/llm/compose.yaml.fixup, src/testdata/models/compose.yaml.fixup, src/testdata/mongo/compose.yaml.fixup, src/testdata/redis/compose.yaml.fixup, src/testdata/static-files/compose.yaml.fixup	LLM, MongoDB, PostgreSQL, Redis, and static-files fixtures now use YAML output and the updated extension metadata where present.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• DefangLabs/defang#1698: Both PRs modify src/pkg/cli/compose/fixup.go’s FixupServices logic around compose service generation.
• DefangLabs/defang#2012: Both PRs touch the model/provider compose fixup path and the generated service shape for LLM-related services.

Suggested labels

go, high

Suggested reviewers

• lionello

Poem

A YAML sprout grew in my burrow today,
with x-defang-llm tucked in bright and gay.
I hopped past ports and networks too,
and fixtures sang a tidy tune.
🐇✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the two main changes: injecting x-defang-llm on model services and converting fixup snapshots to YAML.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch jordan/x-defang-llm-model-runner

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