cpp-style

# clice C++ Coding Style ## Redundancy Is a Defect This is the convention we care most about. Redundant code is not a style nit — it actively misleads: every guard implies the guarded state can occur, every branch implies it can be taken, every parameter implies a caller needs it. When that implication is false, the reader wastes time defending against ghosts. - **Every branch must be reachable.** Before adding a guard or fallback, prove the state can actually occur — construct the input that hits it. If you can't, don't write it. - **No speculative generality.** No parameters, options, hooks, or abstraction layers for hypothetical future callers. Add them when the second real caller arrives. - **One way to do each thing.** Don't leave an old path alive next to its replacement "just in case" — migrate all callers and delete it in the same change. - **Re-read after every change.** Edits leave residue: conditions that became constant, variables read once, branches that now collapse, `else` after `return`, a helper with one remaining caller. Fold them before you're done — simplification that removes a concept beats one that merely shortens lines. - **Delete, don't comment out.** Git history is the archive. - **One behavior difference is one options field.** Two behaviors of the same logic are selected by a boolean in an options struct (`SemanticsOptions{.all_files = true}`), not by a subclass, a dummy collaborator, or a parallel code path. - **Cross-cutting invariants get a single writer.** Accounting, budgets, ownership and visibility guarantees live in one type whose methods are the only transitions and whose doc comment lists the invariants; before coding, grep every site the invariant touches and funnel them through one helper so a missing site is discoverable. Per-site patches never catch up with a reviewer who re-derives the invariant from the whole diff. ## Files & Organization - clice is one C++20 module, `clice`. An interface is a partition, `<stem>.cppm` beside its source, named after its layer and then what it is — usually its path under `src/` (`module clice:vfs.path;`, `unittests.*` under `unittests/`); `pixi run check-layers` checks the layer. A part grown into a directory keeps its interface there under the part's own name (`feature/hover/hover.cppm` is `feature.hover`), beside its implementation units and the internal partitions they share (`feature.hover.card`). Sources are implementation units `.cpp`, entry points `.cc` (`clice.cc`, `src/driver/*.cc`). - A module unit opens with its module declaration, then one `import :<partition>;` per partition it names. The partition `:support.prelude` imports `std.compat`, the C library's names past it (`libc`) and the third-party module (`modules/`), and gives the namespaces clice writes their short names in `clice` — `ranges`, `views`, `chrono`, `this_thread`, `ipc`, `lsp`, `protocol`, `codec`, `json`, `fs`, `sys`, `async`, `deco`, `meta`, `option`, `zest`. The primary interface (`src/module.cppm`) re-exports it, which brings it to every implementation unit; every partition imports it. Code inside `clice` writes those names (`ranges::sort`, `protocol::Range`, `async::task`), never `std::ranges::` or `kotatsu::ipc::protocol::`, and no file declares them again. - No module carries a macro: every compilation force-includes `support/macros.h`, the libraries' (`modules/macros.h`) and clice's own (`*.macros.h`). A unit opens a global module fragment (`module;`) only for a header no module carries, a platform header or `version.h`. - `.h` is left for what a module cannot carry — macros (`*.macros.h`) and platform headers — with `#pragma once`, never include guards. - File names are `snake_case`. - Every file sees the names of all it imports: a file-local helper can clash with a name of another partition or lose overload resolution and ADL to a library function (`llvm::join`) no header used to bring in. - File-local helpers: a single one is `static`; a cluster of them goes in one anonymous namespace. ## Data & Types - `struct` by default, even for types with methods. `class` only when there is a real invariant that private access protects. - `enum class` with an explicit underlying type (e.g. `: std::uint8_t`); document each enumerator with `///` when its meaning is not obvious. - Prefer designated initializers (`{.field = value}`) for aggregate construction. - West const: `const T&`, never `T const&`. - A class lays out its public members first, then its private member functions under one `private:`, then its data members under a second `private:` — functions and fields never interleave. Data members stand one blank line apart, each one's comment on the lines above it, never trailing it. ## Errors, Exceptions & Defense - The project builds with `-fno-exceptions -fno-rtti`: no `throw`/`try`/`catch`, no `dynamic_cast`/`typeid`. Polymorphic inspection uses `llvm::isa<>` / `cast<>` / `dyn_cast<>`. - Fallible synchronous operations return `std::expected<T, E>` with `E` = `std::string` or `std::error_code`; async code uses kotatsu's outcome types. `llvm::Error` only where an LLVM API forces it. - `assert` pins preconditions; impossible branches end in `std::unreachable()` — never `llvm_unreachable` (project convention). - Invalid external input (broken source code, malformed requests) degrades gracefully — empty result, input passed through — it never crashes the server. But graceful degradation is not scattered null checks: per the redundancy rule, defend only against states that can occur. The Debug (ASan + assertions) test surface is the safety net. ## Error Handling (control flow) - Scope an error variable with an `if` init-statement when nothing after the `if` needs it: `if (auto result = foo(); !result.has_value())`. - A type with `operator bool` needs no condition: `if (auto err = foo())`, never `if (auto err = foo(); err)`. - When the success path needs the variable, declare it as a plain local and return early on the error — never an init-statement that forces the success path into an `else`. ## Concurrency & Async - Async code is kotatsu coroutines (`async::task`, `co_await`) — no callback style. A public interface may stay synchronous and drive a coroutine internally when the caller has no event loop (see `Toolchain`). - Review coroutine code by interleavings, not function by function: list every `co_await` suspension point, the events that can fire while it is suspended (crash, respawn, dispatch, cancellation, another coroutine resuming), and trace the shared state through each chain; then check that what the frame captured before suspending is still valid when it resumes. Bugs here are always cross-function interleavings; a function-level read finds none of them. - Cancellation flows down the ownership tree through `task_group::cancel()`; tokens and sources exist only to cross an ownership boundary — the serve mode shutdown source in `MasterServer`, the batch commands' in `Lifetime` (`driver/driver.cppm`). Graceful shutdown is not cancellation — kotatsu has no shield, a cancel cascades all the way down — so a shutdown is a cancellable serving phase bounded by `with_token`, then a non-cancellable drain that joins each task in order. - `cancellation_token::wait()` completes by cancelling itself. Awaited directly inside `when_any` it propagates that cancellation into the parent frame and skips everything after the `co_await`; wrap it in `with_token` (which catches internally) or add `.catch_cancel()`. ## Logging - Log through the `LOG_TRACE` / `LOG_DEBUG` / `LOG_INFO` / `LOG_WARN` / `LOG_ERR` macros (`std::format` syntax, source location captured automatically); `logging::critical` logs and aborts. Never call spdlog directly, never print diagnostics to stdout/stderr. ## Naming Conventions - **Variables, member fields, function names**: `snake_case`. Class member fields do NOT use any special suffix/prefix (no trailing `_`, no `m_` prefix). - **Class names, template parameter names, enum names**: `PascalCase`. Exception: some class names also use `snake_case` — follow the existing style in the project. - **Enum values**: `PascalCase`. - **Acronyms stay uppercase in type names**: `PCHState`, `LSPClient`, `TUIndex` — never `PchState`, `LspClient`. - **A file-local type is named by its role in the file**, without the words of the file's own subject: in an anonymous namespace, `FoldingRangeCollector` in `folding_ranges.cpp` is `Builder`, `ScanOptions` in `scan.cc` is `Options`. A type that is the file's subject itself keeps its name (`Indexer` in `indexer.cpp`). - **Nothing is a `Collector`**: the type producing the file's answer is a `Builder`; a visitor gathering nodes is a `<What>Finder` (`PackForwardFinder`), or is named by what it gathers (`SpelledNames`); a clang callback that only records what clang reports is a `<What>Recorder` (`CompilationUnit::DiagnosticRecorder`). - **Overloads, not prefixes, tell one job's variants apart**: every conversion to the LSP form is a `to_protocol` overload (a second form of the same input is named by the form: `to_symbol_information`), and a feature's answer from the index is an overload of its answer from the AST (`semantic_tokens(SourceText&, …)` beside `semantic_tokens(CompilationUnit&, …)`) — never `semantic_tokens_to_protocol` or `index_semantic_tokens`. - Doc comments on declarations use `///`; the bar for when to write a comment at all is in CLAUDE.md. ## Words to Use and Avoid Identifiers and comments use plain words: the word a newcomer would guess for the thing, not a metaphor or a rare word that needs a glossary (verdict, envelope, ledger). One word means one thing across the codebase — before naming, grep whether the word already means something else nearby, and don't split one concept over two words. A name that its own doc comment has to correct is the wrong name. These were renamed out of the codebase; don't bring them back: | Avoid | Say instead | | --------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | row / rows | an index record: `occurrence` / `relation`, else `entry`; a file's whole index data: `index` / `shard` / `variant`; a source line: `line` | | verdict | `result` / `decision`, whichever the site is | | claim | one word per site: `take`, `acquire`, `reserve`, `cover`, `report` | | envelope | what it is: `TUIndexBlob`, the TU index, a container, a header | | ledger | `table` / `list` | | wire (the serialized form) | `serialized` / `encoded`; "in the protocol" for IPC | | settle | `finish` / `become idle` | | flavor | `kind` / `variant` | | land / landing (a result arriving) | `commit` / `merge` / `finish` | | sweep | `pass` / `run` / `scan`; for cleanup, `remove` | | tier (an encoding choice) | `encoding` (`MaskEncoding`); the search ranking's `NameRank::tier` stays | | surface (verb), vouch for | `report` / `show`, `guarantee` / `confirm` | | stamp outside `vfs` | `version` / `generation` | | collector | `Builder` / `<What>Finder` / `<What>Recorder` (see Naming Conventions) | | `Features`, `Requests` (the server's request entry points) | the request's handler in `LSPClient` (`server/client`), routed by its served project (`ServedProject::pick_route`); the features are `src/feature`'s | | projection | what it is: a document's latest compile (`DocumentCompile`), a result computed from the index (the `SourceText` overloads of `semantic_tokens`), the LSP form; only the indexer's step from the semantic map to entries is a projection (`project_semantics`) | | `switch_source_header` (the feature) | `counterparts`: the files a file pairs with; only the editor command keeps the action's name (`clice.switchSourceHeader`) | | quarantine, barred | the document's crash records (`Session`'s, one `FailureRecord` per request kind); a record `stops` its operation | | strikes | the failure count (`FailureRecord::count`) | | license (to retry) | the retry a change or a save allows; the `Attempt` holding it | | overtaken (an attempt) | `crashed_meanwhile`; a task-graph attempt overtaken by new content keeps the word | | parked (crash records) | nothing: the records live in the document's `Session` and end with it; a reply a test hook holds, or a waiter on an event, is still parked | | `BlameBudget`, blaming a PCH pair | a failure of its consumption (`pch_consume_failed`), a record with a cooldown policy | | evidence (kind) | `feature::RequestKind` | | ticket (outside a request) | a sequence number (`ReindexQueue`'s `seq`); `Ticket` is a request's hold on its buffer | | superseded (a blob) | `previous` | | `PCHFamily`, `PCMFamily`, `PCHBuilder`, `PCMBuilder`, builder (of PCHs, modules) | the PCH and PCM work (`Project::pch_work`, `Project::module_work`) in `project/graph/pch`, `project/graph/pcm`; what both share is `project/graph/precompiled` | | `TURunFamily`, TU run, unit run | a unit's compile (`Project::compile_unit`, `UnitRequest`, `UnitResult`, `NodeKind::Unit`) | | round (of a graph node, of the background index), `RoundContext`, `RoundOutcome` | a graph node's attempt (`Attempt`, `AttemptState`, `Result`); the background index's sweep over its queue is a pass (`BackgroundIndex::run_pass`); round-trip and rounding keep the word |