peridot/docs/lint.md

# Lint

We use clang-tidy to lint C++ code and aim to keep the repository warning-clean.
The linter is configured in the [.clang-tidy](../.clang-tidy) file.

## How to lint

In order to run the current CL through the linter (assuming the current
directory is `//peridot`), run:

```
../scripts/git-file-tidy [--out-dir out/debug-x64]
```

In order to run the entire repository through the linter, add `--all`. You can
also add `--fix` in order to automatically generate fixes for some (but not all)
of the warnings.

## Suppressing warnings

Any warning can be suppressed by adding a `// NOLINT` comment on the line on
which it occurs. It is also possible to disable the check entirely within Ledger
repository by editing the [.clang-tidy](../.clang-tidy) file.

## Disabled checks

This list tracks the reasons for which we disabled particular [checks]:

 - `clang-analyzer-core.NullDereference`, `clang-analyzer-unix.Malloc` - these
    checks are triggering memory access warnings at rapidjson callsites (despite
    the header filter regex) and we didn't find a more granular way to disable
    them
 - `clang-diagnostic-unused-command-line-argument` - ninja-generated compilation
    database contains the linker argument which ends up unused and triggers this
    warning for every file
 - `misc-noexcept*` - Fuchsia doesn't use C++ exceptions
 - `modernize-deprecated-headers` - Fuchsia uses old-style C headers
 - `modernize-raw-string-literal` - the check was suggesting to convert `\xFF`
    literals, which we'd rather keep in the escaped form.
 - `modernize-return-braced-init-list` - concerns about readability of returning
    braced initialization list for constructor arguments, prefer to use a
    constructor explicitly
 - `modernize-use-auto` - not all flagged callsites seemed worth converting to
    `auto`
 - `modernize-use-equals-delete` - flagging all gtest TEST_F
 - `modernize-use-equals-default` - Ledger chose not to impose a preference for
   "= default"
 - `performance-unnecessary-value-param` - it was flagging view classes
   which we prefer to pass by value
 - `readability-implicit-bool-conversion` - Fuchsia C++ code commonly uses implicit
   bool cast of pointers and numbers

[checks]: https://clang.llvm.org/extra/clang-tidy/checks/list.html