Alex Blank
ea006b68c2
The previous sorting fix exposed a deeper bug: ResolvedMount always mounted its staging directory as a single bind mount. When a config profile mount targeted /workspace/x/y and contained a single file z.json, the staging directory (containing only z.json) replaced the ENTIRE /workspace/x/y directory, hiding all sibling files from git repo mounts. - Change apply_resolved_profile to mount each file individually: - source: staging_dir/relative_path - target: expanded_target/relative_path - Sibling files from other mounts are preserved. - Empty mounts produce no volume entries. - Keep volume sorting (parent paths before child paths) which is still necessary for directory mounts and ensures parent dirs exist before file mounts inside them. - Add 4 unit tests for file-level mount behavior. Quality gates: pytest (218 passed, 6 pre-existing), tsc --noEmit (clean)
69 lines
2.5 KiB
Markdown
69 lines
2.5 KiB
Markdown
# Exploration: File-Level Mount Overlays
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## Follow-up to Mount Specificity Ordering
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The sorting fix (parent paths before child paths) was correct for directory mounts,
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but it exposed a deeper bug: `ResolvedMount` always mounts its staging directory
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as a single bind mount. When a config profile mount targets `/workspace/x/y` and
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contains a single file `z.json`, the staging directory (containing only `z.json`)
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replaces the ENTIRE `/workspace/x/y` directory, hiding all sibling files from the
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git repo.
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## Root Cause
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In `apply_resolved_profile`:
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```python
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volume_mounts.append({
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"source": str(mount_dir), # staging dir with ONLY z.json
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"target": expanded_target, # /workspace/x/y
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"type": "bind",
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})
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```
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This mounts a directory. Docker bind mounts at a directory path completely replace
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the target directory. There is no merge.
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## What the User Expects
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Git repo mount: `/repo/x` → `/workspace/x` (directory with many files)
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Config profile mount: `z.json` → `/workspace/x/y/z.json` (single file overlay)
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Expected: `/workspace/x/y/` contains all repo files PLUS the overlaid `z.json`.
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Actual (before sorting): parent mount hides child mount (child never visible).
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Actual (after sorting): child directory mount replaces parent subdirectory
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(`/workspace/x/y` now contains ONLY `z.json`).
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## Solution
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Mount each file individually instead of the staging directory.
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```python
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for file_path, content in mount.files.items():
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full_path = mount_dir / file_path
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full_path.write_text(content)
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volume_mounts.append({
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"source": str(full_path),
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"target": os.path.join(expanded_target, file_path),
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"type": "bind",
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})
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```
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This creates file-level bind mounts. Docker mounts a single file without affecting
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sibling files in the parent directory.
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## Edge Cases
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- Empty `files` dict: skip, no mounts created.
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- Nested file paths (`a/b/c.txt`): mount `staging/a/b/c.txt` → `target/a/b/c.txt`.
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Docker creates parent directories as needed.
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- File target already exists in git repo: file mount wins (desired override behavior).
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- No git repo mount (directory doesn't exist in image): Docker creates parent dirs
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for the first file mount.
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## Sorting Fix Status
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KEEP the sorting. It is still correct and necessary for cases where directory
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mounts genuinely override parent directories (e.g., a git mount to `/workspace/x`
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and another git mount to `/workspace/x/sub`). File-level mounts also benefit from
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sorting because the parent directory mount must exist before file mounts inside it.
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