# Bun Analyzer Developer Gotchas

This document covers common pitfalls and considerations when working with the Bun analyzer.

## 1. Isolated Installs Are Symlink-Heavy

Bun's isolated linker (`bun install --linker isolated`) creates a flat store under `node_modules/.bun/` with symlinks for package resolution. This differs from the default hoisted layout.

**Implications:**
- The analyzer must traverse `node_modules/.bun/**/package.json` in addition to `node_modules/**/package.json`
- Symlink safety guards are critical to prevent infinite loops and out-of-root traversal
- Both logical and real paths are recorded in evidence for traceability
- Performance guards (`MaxSymlinkDepth=10`, `MaxFilesPerRoot=50000`) are enforced

**Testing:**
- Use the `IsolatedLinkerInstallIsParsedAsync` test fixture to verify `.bun/` traversal
- Use the `SymlinkSafetyIsEnforcedAsync` test fixture for symlink corner cases

## 2. `node_modules/.bun/` Scanning Requirement

Unlike Node.js, Bun may store packages entirely under `node_modules/.bun/` with only symlinks in the top-level `node_modules/`. If your scanner configuration excludes `.bun/` directories, you will miss dependencies.

**Checklist:**
- Ensure glob patterns include `.bun/` subdirectories
- Do not filter out hidden directories in container scans
- Verify evidence shows packages from both `node_modules/` and `node_modules/.bun/`

## 3. `bun.lockb` Policy (2025-12-09)

The binary lockfile (`bun.lockb`) remains **unsupported**. We will not parse it and will keep remediation-only handling until Bun publishes a stable, documented format.

**Posture:**
- Treat `bun.lockb` as unsupported input; do not attempt best-effort parsing.
- Emit a deterministic remediation finding instructing conversion to text.
- Skip package inventory when only `bun.lockb` is present to avoid nondeterministic/partial results.

**Migration command (required):**
```bash
bun install --save-text-lockfile
```

This generates `bun.lock` (JSONC text format) which the analyzer parses.

**WebService response when only `bun.lockb` exists:**
- Scan completes with `unsupported` marker for the package manager.
- Remediation guidance is included in findings.
- No package inventory is generated until `bun.lock` is provided.

## 4. JSONC Lockfile Format

`bun.lock` uses JSONC (JSON with Comments) format supporting:
- Single-line comments (`// ...`)
- Multi-line comments (`/* ... */`)
- Trailing commas in arrays and objects

**Parser considerations:**
- The `BunLockParser` tolerates these JSONC features
- Standard JSON parsers will fail on `bun.lock` files
- Format may evolve with Bun releases; parser is intentionally tolerant

## 5. Multi-Stage Build Implications

In multi-stage Docker builds, the final image may contain only production artifacts without the lockfile or `node_modules/.bun/` directory.

**Scanning strategies:**
1. **Image scanning (recommended for production):** Scans the final image filesystem. Set `include_dev: false` to filter dev dependencies
2. **Repository scanning:** Scans `bun.lock` from source. Includes all dependencies by default (`include_dev: true`)

**Best practice:** Scan both the repository (for complete visibility) and production images (for runtime accuracy).

## 6. npm Ecosystem Reuse

Bun packages are npm packages. The analyzer:
- Emits `pkg:npm/<name>@<version>` PURLs (same as Node analyzer)
- Uses `ecosystem = npm` for vulnerability lookups
- Adds `package_manager = bun` metadata for differentiation

This means:
- Vulnerability intelligence is shared with Node analyzer
- VEX statements for npm packages apply to Bun
- No separate Bun-specific advisory database is needed

## 7. Source Detection in Lockfile

`bun.lock` entries include source information that determines package type:

| Source Pattern | Type | Example |
|---------------|------|---------|
| No source / default registry | `registry` | `lodash@4.17.21` |
| `git+https://...` or `git://...` | `git` | VCS dependency |
| `file:` or `link:` | `tarball` | Local package |
| `workspace:` | `workspace` | Monorepo member |

The analyzer records source type in evidence for provenance tracking.

## 8. Workspace/Monorepo Handling

Bun workspaces use a single `bun.lock` at the root with multiple `package.json` files in subdirectories.

**Analyzer behavior:**
- Discovers the root by presence of `bun.lock` + `package.json`
- Traverses all `node_modules/` directories under the root
- Deduplicates packages by `(name, version)` while accumulating occurrence paths
- Records workspace member paths in metadata

**Testing:** Use the `WorkspacesAreParsedAsync` test fixture.

## 9. Dev/Prod Dependency Filtering

The `include_dev` configuration option controls whether dev dependencies are included:

| Context | Default `include_dev` | Rationale |
|---------|----------------------|-----------|
| Repository scan (lockfile-only) | `true` | Full visibility for developers |
| Image scan (installed packages) | `true` | Packages are present regardless of intent |

**Override:** Set `include_dev: false` in scan configuration to exclude dev dependencies from results.

## 10. Evidence Model

Each Bun package includes evidence with:
- `source`: Where the package was found (`node_modules`, `bun.lock`, `node_modules/.bun`)
- `locator`: File path to the evidence
- `resolved`: The resolved URL from lockfile (if available)
- `integrity`: SHA hash from lockfile (if available)
- `sha256`: File hash for installed packages

Evidence enables:
- Tracing packages to their origin
- Validating integrity
- Explaining presence in SBOM

## CLI Reference

### Inspect local workspace
```bash
stellaops-cli bun inspect --root /path/to/project
```

### Resolve packages from scan
```bash
stellaops-cli bun resolve --scan-id <id>
stellaops-cli bun resolve --digest sha256:<hash>
stellaops-cli bun resolve --ref myregistry.io/myapp:latest
```

### Output formats
```bash
stellaops-cli bun inspect --format json > packages.json
stellaops-cli bun inspect --format table
```