ui5-fs

name	ui5-fs
description	Work on the @ui5/fs package: the virtual file system abstraction layer providing Resource, Adapters (FileSystem, Memory), Reader Collections (ReaderCollection, ReaderCollectionPrioritized, DuplexCollection, WriterCollection), specialized readers (Filter, Link, Proxy), resource tagging, monitoring, and the resourceFactory API.
when_to_use	TRIGGER when: the user asks about or wants to modify code related to @ui5/fs, the virtual file system, resources, adapters, reader collections, writer collections, DuplexCollection, resourceFactory, ResourceTagCollection, MonitoredReader, fsInterface, ResourceFacade, or any file within packages/fs/. DO NOT TRIGGER when: the user is working on builder tasks/processors, CLI commands, server middleware, or project graph resolution that does not touch the FS layer.
user-invocable	true

@ui5/fs Skill

You are working on the @ui5/fs package — the virtual file system abstraction layer for UI5 CLI. Read architecture.md in this skill directory for the full architecture reference, including the class hierarchy, API surface, adapter internals, and collection patterns.

Package Location

Source: packages/fs/lib/ Tests: packages/fs/test/lib/ Fixtures: packages/fs/test/fixtures/

Guidelines for Working on This Code

1. Always read the source file before modifying it. The Component Map in architecture.md tells you where each piece lives.
2. Understand the content type state machine. Resources have internal content types (BUFFER, STREAM, FACTORY, DRAINED_STREAM, IN_TRANSFORMATION) with strict transitions. Never bypass modifyStream() for content transformations — it handles mutex locking and state management.
3. Respect the mutex. Resource content access is protected by async-mutex. Concurrent getBuffer() / getString() calls are safe, but modifyStream() acquires an exclusive lock. Never hold a reference to content across an await that could trigger a transformation.
4. Virtual paths are POSIX-absolute. All virtual paths must be absolute POSIX paths (start with /). Base paths must end with /. Adapters normalize patterns relative to their virBasePath.
5. Content parameters are mutually exclusive. When creating a Resource, only one of buffer, string, stream, createStream, or createBuffer can be provided. The createBuffer/createStream factories enable lazy loading.
6. byGlob randomizes result order. AbstractReader.byGlob() intentionally shuffles results to prevent consumers from relying on ordering. Do not assume or depend on glob result order.
7. Clone semantics matter. Resources are cloned on retrieval from adapters. resource.clone() creates an independent copy including content. When modifying resources from collections, understand whether you're working on the original or a clone.
8. ResourceFacade is immutable. ResourceFacade.setPath() throws. The facade wraps a resource with a different virtual path (used by Link reader). Use getOriginalPath() to get the underlying path.
9. Tag format is strict. Tags follow the pattern "namespace:Name" — namespace is lowercase alphanumeric, name is PascalCase. Tags are validated on set. Use ResourceTagCollection or MonitoredResourceTagCollection for tag operations.
10. Test with both FileSystem and Memory adapters. Behavior can differ between adapters (e.g., FileSystem uses globby while Memory uses micromatch; FileSystem has lazy content loading via factories, Memory clones on read).

Known Constraints

• Resource.getStream() is deprecated — use getStreamAsync() or getBuffer() / getString() instead. The deprecation warning is only logged once per process.
• Resource.getStatInfo() is deprecated — use getLastModified(), getSize(), getInode() instead.
• FileSystem adapter's write() uses fs.copyFile for unmodified resources (optimization). It also detects same-source-same-target writes and skips them, but switches to buffer-based writes if the content was modified (to avoid stream read-during-write conflicts).
• Memory adapter auto-creates virtual directory entries in its hierarchy on write().
• WriterCollection matches the longest prefix (greedy match) when routing writes to writers.
• DuplexCollection uses an internal ReaderCollectionPrioritized with the writer first, so written resources shadow the reader's resources.
• fsInterface provides a Node.js fs-compatible wrapper but only implements readFile, stat, and readdir. mkdir is a no-op.
• Resource.getIntegrity() computes SHA-256 via ssri — this triggers full content loading if not already loaded.
• Monitored readers/writers (MonitoredReader, MonitoredReaderWriter) prevent reads/writes after being sealed. They track all access patterns for build caching analysis.

Running Tests

# All tests
npm run unit --workspace=@ui5/fs

# Single file
cd packages/fs && npx ava test/lib/Resource.js

# Verbose with logging
npm run unit-verbose --workspace=@ui5/fs

# Coverage
npm run coverage --workspace=@ui5/fs