fix: avoid partial cache entries when file loading fails

[vibhor-aggr]

Closes #99.

loadFile() previously inserted an empty cache entry before statSync() and readFileSync() completed. If the read failed, the cache could retain a partial object with path but no mtime, letting a later request crash at file.mtime.getTime().

This builds the metadata first and only publishes the cache entry after the file has been read and hashed successfully, while preserving existing per-file metadata such as maxAge.

Verification:

• ./node_modules/.bin/mocha --grep 'partial file data'
• npm test
• git diff --check

Summary by Sourcery

Ensure static file cache entries are only created after files are successfully loaded to avoid partial metadata in the cache.

Bug Fixes:

• Prevent caching of partial file metadata when dynamic file loading fails, avoiding crashes on subsequent requests.

Tests:

• Add a regression test that simulates a read failure and verifies no partial cache entry is stored and that a subsequent successful read is served correctly.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 285b567b-20aa-44ac-bbb6-95830ad20b67

📥 Commits

Reviewing files that changed from the base of the PR and between 182f260 and 1a65596.

📒 Files selected for processing (2)

• index.js
• test/index.js

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[sourcery-ai]

Reviewer's Guide

Refactors file loading to build full metadata objects before inserting them into the cache and adds regression coverage to ensure failed dynamic loads do not leave partial cache entries.

Sequence diagram for updated loadFile cache insertion

sequenceDiagram
  participant Caller
  participant loadFile
  participant fs
  participant files

  Caller->>loadFile: loadFile(name, dir, options, files)
  loadFile->>fs: statSync(filename)
  fs-->>loadFile: stats
  loadFile->>fs: readFileSync(filename)
  fs-->>loadFile: buffer
  loadFile->>loadFile: [build obj metadata]
  loadFile->>files: set(pathname, obj)
  loadFile-->>Caller: obj

Loading

File-Level Changes

Change	Details	Files
Ensure file cache entries are only published after a successful stat and read, preserving existing per-file metadata.	Change loadFile to construct or reuse a metadata object locally without immediately storing it in the cache map. Populate path, cacheControl, maxAge, type, mtime, length, md5, and optional buffer only after fs.statSync and fs.readFileSync succeed. Store the fully populated metadata object back into the cache map once all fields are set.	index.js
Add a regression test that simulates a transient read failure to verify no partial cache entry is stored and subsequent requests succeed.	Introduce mz/fs and os test dependencies to support intercepting readFileSync and creating temporary directories. Add a new test that overrides mzfs.readFileSync to fail once for a specific file while using dynamic, non-preloaded staticCache. Verify that after a 500 response on failed read, no cache entry exists for the file and a subsequent request returns 200 with the correct body.	test/index.js

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#99	Fix the intermittent TypeError 'Cannot read property "getTime" of undefined' when using static-cache for static file hosting.	✅
#99	Add a regression test ensuring that failed dynamic file loads do not leave partial cache entries that can cause runtime errors later.	✅

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[sourcery-ai]

Hey - I've left some high level feedback:

• In the new test, you're monkeypatching mzfs.readFileSync, but loadFile uses fs.readFileSync, so the failure path you're trying to exercise may never be hit; consider patching the actual fs.readFileSync (or whatever the production code uses) to ensure the test is meaningful.
• To make the new test more robust, you could guard cleanup() with try/catch or use fs.rmSync(dir, { recursive: true, force: true }) so failures during unlink/rmdir don't mask assertions or leak resources when the test fails midway.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In the new test, you're monkeypatching `mzfs.readFileSync`, but `loadFile` uses `fs.readFileSync`, so the failure path you're trying to exercise may never be hit; consider patching the actual `fs.readFileSync` (or whatever the production code uses) to ensure the test is meaningful.
- To make the new test more robust, you could guard `cleanup()` with try/catch or use `fs.rmSync(dir, { recursive: true, force: true })` so failures during unlink/rmdir don't mask assertions or leak resources when the test fails midway.

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[vibhor-aggr]

Thanks for the review. I rechecked the current head 1a65596f89913c57ef7b7d75e48f89467af91004. The partial-cache regression test patches mz/fs.readFileSync, which is the same module instance used by production loadFile() in index.js, so the dynamic load failure path is exercised. The cleanup path also restores the monkeypatch, closes the server, and guards file/directory removal so cleanup failures do not mask assertions.

Verified locally with Node v24.16.0:

• ./node_modules/.bin/mocha --grep "partial file data": 1 passing
• npm test: 38 passing
• git diff --check master..HEAD: passed