# Precious - One Code Quality Tool to Rule Them All

Who doesn't love linters and tidiers (aka pretty printers)? I sure love them. I love them so much that in many of my projects I might have five or ten!

Wouldn't it be great if you could run all of them with just one command? Wouldn't it be great if that command just had one config file to define what tools to run on each part of your project? Wouldn't it be great if Sauron were our ruler?

Now with Precious you can say "yes" to all of those questions.

## TLDR

Precious is a code quality tool that lets you run all of your linters and tidiers with a single command. It's features include:

- One file, `precious.toml`, defines all of your linter and tidier commands, as well as what files they operate on.
- Respects VCS ignore files and allows global and per-command excludes.
- Language-agnostic, and it works the same way with single- or multi-language projects.
- Easy integration with commit hooks and CI systems.
- Commands are executed in parallel by default, with one process per CPU.
- Commands can be grouped with labels, for example to just run a subset of commands for commit hooks and all commands in CI.

## Installation

There are several ways to install this tool.

### Use ubi

Install my universal binary installer (ubi) tool and you can use it to download `precious` and many other tools.

    $> ubi --project houseabsolute/precious --in ~/bin

### Binary Releases

You can grab a binary release from the releases page. Untar the tarball and put the executable it contains somewhere in your path and you're good to go.

### Cargo

You can also install this via `cargo` by running `cargo install precious`. See the cargo documentation to understand where the binary will be installed.

## Getting Started

The `precious` binary has a `config init` subcommand that will generate a config file for you. This subcommand takes the following flags:

| Flag | Description | | --------------------------------- | ---------------------------------------------------------------------------------- | | `-c`, `--component` `<COMPONENT>` | The component(s) to generate config for (see below) | | `-p`, `--path` `<PATH>` | The path to which the config file should be written. Defaults to `./precious.toml` |

Here's an example for a Rust project:

    $> precious config init --component rust --component gitignore --component yaml

### Components

The following components are supported:

- `go` - Generates config for a Go project which uses `golangci-lint` for linting and tidying.
- `perl` - Generates config for a Perl project which uses a variety of tools, including `perlcritic` and `perltidy`.
- `rust` - Generates config for a Rust project which uses `rustfmt` for tidying and `clippy` for linting.
- `gitignore` - Generates config to lint and tidy (by sorting) `.gitignore` files using `omegasort`.
- `markdown` - Generates config to lint and tidy Markdown files using `prettier`.
- `yaml` - Generates config to lint and tidy YAML files using `prettier`.

### Examples

This repo's examples directory has `precious.toml` config files for several languages. Contributions for other languages are welcome!

The config in the examples matches what `precious config init` generates, and there are comments in the files with more details about how you might change this configuration.

Also check out the example `install-dev-tools.sh` script for a tool to install all of your project's linting and tidying dependencies. You can customize this as needed to install only the tools you need for your project.

## Configuration

Precious is configured via a single `precious.toml` or `.precious.toml` file that lives in your project root. The file is in TOML format.

There is just one key that can be set in the top level table of the config file:

| Key | Type | Required? | Description | | --------- | ---------------- | --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | `exclude` | array of strings | no | Each array member is a pattern that will be matched against potential files when `precious` is run. These patterns are matched in the same way as patterns in a gitignore file. You can use lines starting with a `!` to negate the meaning of previous rules in the list, so that anything that matches is not excluded even if it matches previous rules. |

All other configuration is on a per-command basis. A command is something that either tidies (aka pretty prints or beautifies), lints, or does both. These commands are external programs which precious will execute as needed.

Each command is defined in a block named something like `[commands.command-name]`. Each name after the `commands.` prefix must be unique. You can have run the same executable differently with different commands as long as each command has a unique name.

Commands are run in the same order as they appear in the config file.

### Command Invocation

There are three configuration keys for command invocation. All of them are optional. If none are specified, `precious` defaults to this:

    invoke      = "per-file"
    working_dir = "root"
    path_args   = "file"

This runs the command once per file with the working directory for the command as the project root. The command will be passed a relative path to the file from the root as a single argument to the command.

#### `invoke`

The `invoke` key tells `precious` how the command should be invoked.

| Value | Description | | ------------ | ---------------------------------------------------------------------- | | `"per-file"` | Run this command once for each matching file. This is the default. | | `"per-dir"` | Run this command once for each matching directory. | | `"once"` | Run this command once. |

#### `working_dir`

The `working_dir` key tells precious what the working directory should be when the command is run.

| Value | Description | | -------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `"root"` | The working directory is the project root. This is the default. | | `"dir"` | The working directory is the directory containing the matching files. This means `precious` will `chdir` into each matching directory in turn as it executes the command. | | `.chdir_to = "path"` | The working directory will be the given path when executing the command. This path must be relative to the project root. |

##### `working_dir.chdir_to = "path"`

The final option for `working_dir` is to set an explicit path as the working directory.

With this option, the working directory will be set to the given subdirectory when the command is executed. Relative paths passed to the command will be relative to this subdirectory rather than the project root.

#### `path_args`

The `path_args` key tells precious how paths should be passed when the command is run.

| Value | Description | | ----------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `"file"` | Passes the path to the matching file relative to the root. This is the default. With `working_directory.chdir_to` the path is relative to the given working directory. | | `"dir"` | Passes the path to the directory containing the matching files relative to the root. With `working_directory.chdir_to` the path is relative to the given working directory. | | `"none"` | No paths are passed to the command at all. | | `"dot"` | Always pass `.` as the path. This is useful when `working_dir = "dir"` and the command still requires a path to be passed. | | `"absolute-file"` | Passes the path to the matching file as an absolute path from the filesystem's root directory. | | `"absolute-dir"` | Passes the path to the directory containing the matching files as an absolute path from the filesystem's root directory. |

#### Nonsensical Combinations

Most combinations of these configuration keys are allowed, but there are some nonsensical combinations that will cause `precious` to exit with an error.

    invoke = "per-file"
    path_args = "dir", "none", "dot", or "absolute-dir"

You cannot invoke a command once per file without passing the filename.

    invoke = "per-dir"
    path_args = "none" or "dot"
    working_dir = "root"
    # ... or ...
    working_dir.chdir_to = "whatever"

You cannot invoke a command once per directory from a root without passing the directory name or a list of file names. If you want to run a command once per directory with no path arguments or using `.` as the path then you must set `working_dir = "dir"`.

    invoke = "once"
    working_dir = "dir"

You cannot invoke a command once if the working directory is set to each matching directory in turn.

#### Invocation Examples

See the Invocation Examples documentation for comprehensive examples of every possible set of options.

### Other Per-Command Configuration Keys

The other keys allowed for each command are as follows:

| Key | Type | Required? | Applies To | Default | Description | | ------------------------- | ---------------------------- | --------- | ------------------------ | ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `type` | string | yes | all | | This must be either `lint`, `tidy`, or `both`. This defines what type of command this is. A command which is `both` must define `lint_flags` or `tidy_flags` as well. | | `include` | string or array of strings | yes | all | | Each array member is a gitignore pattern that tells `precious` what files this command applies to. You can use lines starting with a `!` to negate the meaning of previous rules in the list, so that anything that matches is not included even if it matches previous rules. | | `exclude` | string or array of strings | no | all | | Each array member is a gitignore pattern that tells `precious` what files this command should not be applied to. You can use lines starting with a `!` to negate the meaning of previous rules in the list, so that anything that matches is not excluded even if it matches previous rules. | | `cmd` | string or array of strings | yes | all | | This is the executable to be run followed by any arguments that should always be passed. | | `env` | table - values are strings | no | all | | This key allows you to set one or more environment variables that will be set when the command is run. The values in this table must be strings. | | `path_flag` | string | no | all | | By default, `precious` will pass the path being operated on to the command it executes as the final, positional, argument(s). If the command takes paths via a flag you need to specify that flag with this key. | | `lint_flags` | string or array of strings | no | combined linter & tidier | | If a command is both a linter and tidier then it may take extra flags to operate in linting mode. This is how you set that flag. | | `tidy_flags` | string or array of strings | no | combined linter & tidier | | If a command is both a linter and tidier then it may take extra flags to operate in tidying mode. This is how you set that flag. | | `ok_exit_codes` | integer or array of integers | yes | all | | Any exit code that does not indicate an abnormal exit should be here. For most commands this is just `0` but some commands may use other exit codes even for a normal exit. | | `lint_failure_exit_codes` | integer or array of integers | no | linters | | If the command is a linter then these are the status codes that indicate a lint failure. These need to be specified so `precious` can distinguish an exit because of a lint failure versus an exit because of some unexpected issue. | | `ignore_stderr` | string or array of strings | all | all | | By default, `precious` assumes that when a command sends output to `stderr` that indicates a failure to lint or tidy. This parameter can specify one or more regexes. These regexes will be matched against the command's stderr output. If any of the regexes match, the stderr output is ignored. | | `labels` | string or array of strings | all | all | | One or more labels used to categorize commands. See below for more details. |

### Referencing the Project Root

For commands that can be run from a subdirectory, you may need to specify config files in terms of the project root. You can do this by using the string `$PRECIOUS_ROOT` in any element of the `cmd` configuration key. So for example you might write something like this:

    cmd = ["some-tidier", "--config", "$PRECIOUS_ROOT/some-tidier.conf"]

The `$PRECIOUS_ROOT` string will be replaced by the absolute path to the project root.

## Running Precious

To get help run `precious --help`.

The root command takes the following flags:

| Flag | Description | | --------------------------- | ------------------------------------------------------------------- | | `-c`, `--config` `<config>` | Path to the precious config file | | `-j`, `--jobs` `<jobs>` | Number of parallel jobs (threads) to run (defaults to one per core) | | `-q`, `--quiet` | Suppresses most output | | `-a`, `--ascii` | Replace super-fun Unicode symbols with terribly boring ASCII | | `-v`, `--verbose` | Enable verbose output | | `-V`, `--version` | Prints version information | | `-d`, `--debug` | Enable debugging output | | `-t`, `--trace` | Enable tracing output (maximum logging) | | `-h`, `--help` | Prints help information |

### Parallel Execution

Precious will always execute commands in parallel, with one process per CPU by default. The execution is parallelized based on the command's invocation configuration. For example, on a 12 CPU system, a command that has `invoke = "per-file"` will be executed up to 12 times in parallel, with each command execution receiving one file.

You can disable parallel execution by passing `--jobs 1`.

### Subcommands

The `precious` command has three subcommands, `lint`, `tidy`, and `config`. You must always specify one of these. The `lint` and `tidy` commands take the same flags:

#### Selecting Paths to Operate On

When you run `precious` you must tell it what paths to operate on. There are several flags for this:

| Mode | Flag | Description | | ------------------------------------------------------------ | --------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | All paths | `-a`, `--all` | Run on all files under the project root (the directory containing the precious config file). | | Modified files according to git | `-g`, `--git` | Run on all files that git reports as having been modified, including staged files. | | Staged files according to git | `-s`, `--staged` | Run on all files that git reports as having been staged. | | Staged files according to git, with unstaged changes stashed | `--staged-with-stash` | This is like `--stashed`, but it will stash unstaged changes while it runs and pop the stash at the end. This ensures that commands only run against the staged version of your codebase. This can cause issues with many editors or other tools that watch for file changes, so exercise care with this flag. | | Paths given on CLI | | If you don't pass any of the above flags then `precious` will expect one or more paths to be passed on the command line after all other flags. If any of these paths are directories then that entire directory tree will be included. |

#### Running One Command

You can tidy or lint with just a single command by passing the `--command` flag:

    $> precious lint --command some-command --all

The name passed to `--command` must match the name of the command in your config file. So in the above example, this would look for a command defined as `[commands.some-command]` in your config.

#### Selecting Commands With Labels

Each command can be assigned one or more labels. This lets you create arbitrary groups of commands. Then when you tidy or lint you can pick a label by passing a `--label` flag:

    $> precious lint --label some-label --all

The way labels work is as follows:

- A command without a `labels` key in its config has one label, `default`.
- Running `tidy` or `lint` without a `--label` flag uses the `default` label.
- If you assign `labels` to a command and you want that command included in the `default` label, you must explicitly include it:

      [command.some-command]
      # ...
      labels = [ "default", "some-label" ]

#### Default Exclusions

When selecting paths `precious` always respects your ignore files. Right now it only knows how this works for git, and it will respect all of the following ignore files:

- Per-directory `.ignore` and `.gitignore` files.
- The `.git/info/exclude` file.
- Global gitignore globs, usually found in `$XDG_CONFIG_HOME/git/ignore`.

This is implemented using the rust `ignore` crate, so adding support for other VCS systems should be proposed there.

In addition, you can specify excludes for all commands by setting a global `exclude` key.

Finally, you can specify per-command `include` and `exclude` keys.

#### How Include and Exclude Are Applied

When `precious` runs it does the following to determine which commands apply to which paths.

- The base files to operate on are selected based on the command line flag specified. This is one of:
  - `--all` - All files under the project root (the directory containing the precious config file).
  - `--git` - All files in the git repo that have been modified, including staged files.
  - `--staged` - All files in the git repo that have been staged.
  - paths passed on the CLI - If a path is a file it is added to the list as-is. If the path is a directory then all the files under that directory (recursively) are found.
- VCS ignore rules are applied to remove files from this list.
- The global exclude rules are applied to remove files from this list.
- Based on the command's `invoke` key, a list of files to be checked is generated and the command's include/exclude rules are applied. To be included, a file must match at least one include rule and not match any exclude rules to be accepted.
  - If `invoke` is `per-file`, then the rules are applied one file at a time.
  - If `invoke` is `per-dir`, then if any file in the directory matches the rules, the command will be run on that directory.
  - If `invoke` is `once`, then the rules are applied to all of the files at once. If any one of those files matches the include rule, the command will be run.

## Configuration Recommendations

Here are some recommendations for how to get the best experience with precious.

### Choosing How to `invoke` the Command

Some commands might work equally well with `invoke` set to either `per-dir` or `root`. The right run mode to choose depends on how you are using precious.

In general, if you either have a very small set of directories, or you are running precious on most or all of the directories at once, then `once` will be faster.

However, if you have a larger set of directories and you usually only need to lint or tidy a small subset of these at once, then `per-dir` mode will be faster.

### Quiet Flags

Many commands will accept a "quiet" flag of some sort. In general, you probably do not want to run commands in a quiet mode with precious.

In the case of a successful tidy or lint command execution, precious already hides all stdout from the command that it runs. If the command fails somehow, precious will print out the command's stdout and stderr output.

By default, precious treats any output to stderr as an error in the command (as opposed to a linting failure). You can use the `ignore_stderr` to specify one or more regexes for allowed stderr output.

In addition, you can see all stdout and stderr output from a comment by running precious in `--debug` mode.

All of which is to say that in general there's no value to running a command in quiet mode with precious. All that does is make it harder to debug issues with that command when lint checks fail or other issues occur.

## Exit Codes

When running in `--tidy` mode, precious always exits with `0`, whether or not any files are tidied.

When running in `--lint` mode, precious will exit with `0` when all files pass linting. If any lint commands fail it will exit with `1`.

In both modes, if any commands fail, either by returning exit codes that aren't listed as ok or by printing to stderr unexpectedly, then precious will exit with a non-0 exit code.

## Common Scenarios

There are some configuration scenarios that you may need to handle. Here are some examples:

### Command runs just once for the entire source tree

Some commands, such as rust-clippy, expect to run just once across the entire source tree, rather than once per file or directory.

In order to make that happen you should use the following config:

    include = "**/*.rs"
    invoke = "once"
    path_args = "dot" # or "none"

This will cause `precious` to run the command exactly once in the project root.

### Command runs in the same directory as the files it lints and does not accept path arguments

If you want to run the command without passing the path being operated on to the command, set `invoke = "per-dir"` and `path_args = "none"`:

    include   = "**/*.rs"
    invoke    = "per-dir"
    path_args = "none"

### You want a command to exclude an entire directory (tree) except for one or more files

Use an ignore pattern starting with `!` in the `exclude` list:

    [commands.rustfmt]
    type    = "both"
    include = "**/*.rs"
    exclude = [
        "path/to/dir",
        "!path/to/dir/included.rs",
    ]
    cmd     = ["rustfmt"]
    lint_flags = "--check"
    ok_exit_codes = [0]
    lint_failure_exit_codes = [1]

### You want to run Precious as a commit hook

Simply run `precious lint -s` in your hook. It will exit with a non-zero status if any of the lint commands indicate a linting problem.

### You want to run commands in a specific order

As of version 0.1.2, commands are run in the same order as they appear in the config file.