## Summary
Initial integration of `CompileGraph` (#375) into `MasterServer`,
enabling basic end-to-end C++20 module support: on-demand PCM building,
dependency-ordered compilation, cascade invalidation on save, and
diagnostic integration.
This is a **first-pass implementation** — the core pipeline works, but
there are known areas for follow-up:
- PCM files go to system temp dir instead of `.clice/cache/`; no disk
cleanup on invalidation
- `run_build_drain` scans imports itself rather than delegating fully to
CompileGraph
- No incremental/partial rebuild (full PCM rebuild on any change)
- Cycle detection is tested at unit level but integration-level coverage
is minimal
## Changes
### Module dependency compilation (`master_server.cpp`)
Before sending a file to the stateful worker, `run_build_drain` now:
1. Scans imports via `scan_precise()` to discover module dependencies
2. Compiles each dep through `compile_graph->compile()`, which
recursively builds transitive PCMs
3. Handles implementation units — `module M;` implicitly needs the
interface PCM
4. Passes all built PCMs to the stateful worker, excluding the file's
own PCM
5. Skips compile on dep failure and resets `build_running` /
`drain_scheduled`
6. Re-lookups iterators after `co_await` to avoid use-after-invalidation
### Cascade invalidation (`didSave` / `didClose`)
- `didSave`: calls `compile_graph->update()` to mark transitive
dependents dirty, removes stale PCM paths, schedules rebuilds for open
dirtied files
- `didClose`: cancels in-flight compilations for the closed file
### Other fixes in this PR
- Debounce timers switched to `shared_ptr` to prevent use-after-free
when `didClose` destroys the timer mid-wait
- `fill_compile_args` returns `bool`; callers handle empty CDB
gracefully
- Adapt all `PositionMapper` call sites to the new `optional` return API
from eventide
## Test plan
- [x] 25 C++ unit tests for CompileGraph (cycles, partial failure,
cancel, update, empty graph)
- [x] 24 C++ integration tests with real clang PCM compilation
- [x] 3 worker-level module tests (BuildPCM, PCM-dependent compile,
multi-module)
- [x] 26 Python LSP integration tests (single module through circular
deps, hover, error diagnostics)
- [x] 371 unit tests + 54 integration tests pass
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
## Summary
Add `CompileGraph`, a pull-based async scheduler for C++20 module
compilation. When a file is compiled that imports modules, the graph
automatically resolves, builds, and caches PCM dependencies in the
correct order before the main compile proceeds.
## Design
### Data model
Each compilation unit (`CompileUnit`) tracks:
- `dependencies` / `dependents` — forward and reverse dependency edges
- `dirty` / `compiling` — current state flags
- `generation` — monotonic counter incremented by `update()`, used for
ABA-safe stale detection
- `source` + `completion` — cancellation token source and completion
event for cooperative async
### `compile(path_id)` — pull-based compilation
Lazily resolves dependencies (via `resolve_fn`) on first access, then
recursively compiles all transitive deps before dispatching the unit
itself:
- **Concurrent**: sibling deps compiled in parallel via `when_all`
- **Dedup**: diamond dependencies (A->B->D, A->C->D) — the second branch
waits on the first via `completion.wait()` instead of re-compiling
- **Cycle detection**: per-branch `ancestors` set (passed by value)
catches direct cycles; `has_wait_cycle()` BFS catches cross-branch
cycles (e.g. `1->{2,3}, 2->3, 3->2`) that would deadlock at
`completion.wait()`
- **Cancellation**: all `co_await` wrapped with `with_token()`, so
`update()` can cancel in-flight compilations immediately
- **Generation check**: captures generation counter before `co_await`;
if `update()` bumped it during dispatch, the result is discarded (unit
stays dirty)
### `update(path_id)` — cascade invalidation
BFS along `dependents` edges to mark the entire reverse-transitive
closure as dirty. For the source node, clears `resolved` and dependency
edges so they are re-scanned on next compile. Cancels any in-flight
compilations via `source->cancel()`.
## Test plan
22 unit tests covering:
- [x] No deps, single dep, chain, diamond (compile ordering + dedup)
- [x] Update invalidation, cascade through chains and diamonds
- [x] Re-resolution after update (deps can change)
- [x] Stale back-edge cleanup
- [x] Direct cycle detection (A->B->A)
- [x] Cross-branch cycle detection (when_all deadlock case)
- [x] Self-loop
- [x] Dispatch failure propagation
- [x] cancel_all + recompile
- [x] Update during in-flight compile (cancellation + generation check)
- [x] CI green on Linux, macOS, Windows
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
