fix(ci): use per-call temp dir in DNA templating to fix race-condition flake

[HexaField]

Summary

read_and_template_holochain_dna (in rust-executor/src/languages/mod.rs) used temp_dir().join(source_language_hash) as its working directory, so every templating call against the same source language landed on the same /tmp/<hash>/ path. The top of the function wipes that path via fs::remove_dir_all before recreating it — which means concurrent calls against the same source language race each other.

Two integration tests in tests/js/tests/neighbourhood.ts both call languages.applyTemplateAndPublish(DIFF_SYNC_OFFICIAL, ...) against the shared perspective-diff-sync hash:

• can be created by Alice and joined by Bob
• shared link created by Alice received by Bob

On busy CircleCI workers the second call regularly enters the function while the first is still mid-pipeline (between unpack_happ and pack_happ). The second call's fs::remove_dir_all wipes the first's working directory, and the first's eventual pack_happ blows up with:

Failed to pack hApp: ffs::IoError at path
'/tmp/QmzSY…/happ/happ.yaml': No such file or directory (os error 2)

This has been the long-standing flake on integration-tests-js. It surfaced again under the #837 / #842 stack and has been recurring across CI runs.

Fix

Switch to a per-call UUID-suffixed temp dir:

let temp_templating_path = std::env::temp_dir().join(format!(
    "{}-{}",
    source_language_hash,
    uuid::Uuid::new_v4()
));

• Concurrent templates can no longer race on the same path.
• The existing end-of-function fs::remove_dir_all(&temp_templating_path) still removes the per-call dir on the happy path.
• An earlier-failing call only leaves a uniquely-named orphan rather than poisoning the next call.
• uuid is already a workspace dependency (uuid = "1.3.0").

Test plan

• cargo check -p ad4m-executor --lib clean
• cargo fmt --check clean
• Full CircleCI integration-tests-js green on this branch

Summary by CodeRabbit

• Bug Fixes
  • Fixed intermittent failures in DNA/HApp templating operations that occurred when multiple concurrent invocations were processed simultaneously. The system now properly isolates concurrent operations to prevent them from interfering with each other's intermediate artifacts.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1aa33d17-156a-4ce9-b44b-646d3a405112

📥 Commits

Reviewing files that changed from the base of the PR and between f3882a5 and f667453.

📒 Files selected for processing (1)

• rust-executor/src/languages/mod.rs

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📝 Walkthrough

Walkthrough

The read_and_template_holochain_dna function now appends a UUID to the source language hash when creating its temporary working directory, replacing the shared hash-only path. This prevents concurrent invocations from racing on the same directory and deleting each other's intermediate artifacts during template and publish operations.

Changes

DNA Templating Concurrency Fix

Layer / File(s)	Summary
Per-invocation unique temp directory rust-executor/src/languages/mod.rs	The temporary working directory for DNA/HApp templating operations now includes a UUID suffix appended to the source language hash, isolating each invocation's unpack/pack artifacts and preventing race conditions where concurrent calls would overwrite or delete each other's files mid-pipeline.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A race once plagued the temp-dir lane,
Where files collided, chaos reigned.
Then UUID came, a bunny's delight,
Each call gets its own unique site!
No more stepping on paws today,
Concurrency fixed in the rabbit's way! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and specifically summarizes the main change: fixing a race condition in DNA templating by using per-call temporary directories instead of shared hash-only paths.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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.

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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 fix/ci-template-dna-race-condition

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