refactor: introduce Workspace/Session state model and clarify component responsibilities (#406)
## Summary
Introduces a two-layer state model that cleanly separates disk-based
project state from per-open-file editing state, and redistributes
responsibilities across server components so each has a single, clear
role.
## New types
**Workspace** — all persistent, project-wide shared state:
- CompilationDatabase, PathPool, DependencyGraph, CompileGraph
- path_to_module mapping, PCH cache, PCM cache, PCM paths
- ProjectIndex, MergedIndex shards
- CliceConfig
- Methods: on_file_saved(), on_file_closed(), load/save/cleanup_cache(),
build_module_map(), fill_pcm_deps(), cancel_all()
**Session** — volatile per-open-file editing state:
- text, version, generation, ast_dirty
- pch_ref (references Workspace.pch_cache), ast_deps, header_context
- file_index (OpenFileIndex for unsaved buffer)
- path_id member for self-identification
## Component responsibilities after refactor
| Component | Role | Owns state? |
|-----------|------|-------------|
| **Workspace** | Disk truth + shared caches | Yes (all project state) |
| **Session** | One open file editing state | Yes (per-file only) |
| **Compiler** | Compilation pipeline, worker communication | No
(references only) |
| **Indexer** | Index queries + background indexing scheduling |
Scheduling state only |
| **MasterServer** | LSP protocol dispatch + lifecycle coordination |
sessions map |
## What moved where
**Into Workspace** (from Compiler/MasterServer):
- PCH/PCM cache management (load_cache, save_cache, cleanup_cache)
- Module map building (build_module_map, fill_pcm_deps)
- File lifecycle hooks (on_file_saved, on_file_closed)
- cancel_all, OpenFileIndex/MergedIndexShard type definitions
**Into Session** (from Compiler documents map):
- Document text, version, generation, ast_dirty
- PCH reference, dependency snapshot, header context
**Into Indexer** (from MasterServer):
- Background indexing queue, scheduling state, idle timer
- schedule(), enqueue(), run_background_indexing()
**Into syntax/completion.h** (from Compiler):
- detect_completion_context() — pure text parsing
- complete_module_import() — prefix match on module names
- complete_include_path() — directory listing against search paths
**Inlined into MasterServer** (from Compiler):
- didOpen/didChange/didClose/didSave handlers
- switchContext/currentContext
- publish_diagnostics/clear_diagnostics
**Deleted from Compiler** (9 methods):
- open_document, apply_changes, close_document, on_save
- switch_context, get_active_context, invalidate_host_contexts
- on_file_closed, on_file_saved, complete_include, complete_import
## Tests
- 481 tests pass (465 existing + 16 new completion tests)
- New: tests/unit/syntax/completion_tests.cpp
## Diff stats
15 files changed, +1857, -1555
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
## Release Notes
* **New Features**
* Enhanced completion support for include paths and module imports with
improved context detection.
* Added background indexing system for automatic project symbol
indexing.
* **Bug Fixes**
* Improved reliability of document change tracking and compilation state
management.
* Better handling of header file compilation contexts.
* **Tests**
* Added unit tests for completion context detection and module/include
path completion.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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