RawExecutionDriver ignores getHandles — writeResource produces empty dataArtifacts

[umag]

Description

Extension model methods that call context.writeResource() succeed but produce empty dataArtifacts: [] in the output. This affects ALL extension models using the default raw execution driver.

Steps to Reproduce

1. Create any extension model with a method that calls context.writeResource()
2. Run the method: swamp model method run <name> <method> --json
3. Observe "dataArtifacts": [] in the output despite the method succeeding

Example with the @tubearchivist/api extension:

swamp model method run tubearchivist stats --json
# Returns: "dataArtifacts": [], "status": "succeeded"

The API call succeeds, writeResource is called, but no data artifacts are produced.

Root Cause

In src/domain/drivers/raw_execution_driver.ts (lines 89-147):

1. createResourceWriter() returns { writeResource, getHandles } but only writeResource is destructured — getHandles is ignored (line 89-91)
2. writeResource is injected into the context and correctly persists data to disk
3. After method execution, the driver reads result.dataHandles from the method's return value (line 144)
4. User extension methods return {} (no dataHandles property), so result.dataHandles is undefined
5. The driver falls back to [] via result.dataHandles ?? []

The handles accumulated by createResourceWriter via getHandles() are never collected.

Expected Behavior

dataArtifacts should contain the handles for all resources written via context.writeResource() during method execution.

Suggested Fix

In RawExecutionDriver.execute():

• Also destructure getHandles from createResourceWriter()
• After method execution, fall back to getHandles() when result.dataHandles is empty:

const writerHandles = getHandles();
const allHandles = result.dataHandles?.length ? result.dataHandles : writerHandles;
const outputs = allHandles.map((handle) => ({ kind: "persisted" as const, handle }));

This mirrors how the Docker execution driver works — it captures resources from the runner's output array rather than relying on the method's return value.

Affected Component

src/domain/drivers/raw_execution_driver.ts — the default execution driver for all extension models.

Environment

• swamp version: 20260328.174132.0-sha.5388e901
• Platform: macOS Darwin 23.6.0

[github-actions]

Hi @umag, thanks for opening this issue!

We appreciate you taking the time to report it. A maintainer will review it as soon as possible.

In the meantime, please make sure you've included all relevant details (steps to reproduce, expected vs actual behaviour, swamp version, etc.) to help us triage it quickly.

[stack72]

🔍 Triage started — fetching issue context

[stack72]

📋 Classified as bug (high) — Confirmed by code reading: RawExecutionDriver destructures only writeResource from createResourceWriter() (line 89-91) and only createFileWriter from createFileWriterFactory() (line 106-119), ignoring getHandles from both. After method execution, it reads result.dataHandles (line 144) which is undefined for extension methods that return {}. The handles accumulated by the writers are never collected.

[stack72]

📝 Implementation plan generated (v1) — Fix RawExecutionDriver to collect handles from createResourceWriter and createFileWriterFactory getHandles() functions, falling back to those when the method result has no dataHandles. This is a 2-step fix: patch the driver, add tests.

[stack72]

🔍 Adversarial review (plan v1)

• ADV-1 [low/correctness]: The plan should clarify the merge strategy: use writer-accumulated handles only when result.dataHandles is undefined or empty (length 0). Built-in models return the same handles from both paths, so fallback is safe. But the code should use result.dataHandles?.length ? result.dataHandles : writerHandles to be explicit.
• ADV-2 [low/testing]: The plan references raw_execution_driver_test.ts which doesn't exist yet. This is expected (new file), but should also verify no existing integration tests break — run the full test suite after the fix.
• ADV-3 [medium/correctness]: File writer handles are only added to getHandles() after finalize/writeAll/writeText/writeStream completes (the factory wraps these methods to push handles). If an extension method creates a file writer but doesn't finalize it, those handles won't be captured. The driver should document this contract or add a warning.

✅ No blocking findings — ready for approval

[stack72]

🔄 Plan revised (v2) — incorporated feedback round 1