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
-a, --auto	Automatically determines what components to create
-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

You must pass either --auto or at least one --component. In --auto mode, precious will look at all the files in your project and generate config based on the types of files it finds.

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.
• shell - Generated config which uses shfmt for tidying and shellcheck 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.
• toml - Generates config to lint and tidy TOML files using taplo.
• 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.

There are some experimental options for the invoke key as well. The exact names or the details of how they operate may change in a future release.

Value	Description
.per‑file‑or‑dir = n	If the number of matching files is less than n, run this command once for each matching file. Otherwise run it once for each matching directory.
.per‑file‑or‑once = n	If the number of matching files is less than n, run this command once for each matching file. Otherwise run it once.
.per‑dir‑or‑dir = n	If the number of matching directories is less than n, run this command once for each matching directory. Otherwise run it once.

These are written like this:

[commands.some-command]
invoke.per-file-or-dir = 42

These experimental options are useful for optimizing the speed of running a command. In some cases, a command can be run in multiple ways, and how quickly it completes depends on how many files or directories need to be linted or tidied.

The golangci-lint tool is a good example. Invoking it multiple times for a few directories can be much faster than running it against the entire repo. However, once there are enough directories to check, invoking it once for the entire repo will be faster.

Note that the path-args setting needs to work with both possible cases for these options. For golangci-lint, that means setting it to dir when using per-dir-or-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.
Files that differ from a given git ref	-d <REF>, ‑‑git‑diff‑from	Run on all files in the current HEAD that differ from the given <REF>. The value <REF> can be a branch name, like master, or an ref name like HEAD~6 or master@{2.days.ago}. See git help rev-parse for more options. Note that this will not see files with uncommitted changes in the local working directory.
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. Be careful when using this option in scripts because of this issue.
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

Labels work 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.
  • --git-diff-from <REF> - All files in the current HEAD that differ from <REF>.
  • 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.

The config Subcommand

In addition to the init subcommand, this command has a list subcommand. This prints a Unicode table describing the commands in your config file.

Found config file at: /home/autarch/projects/precious/precious.toml

┌─────────────────────┬──────┬────────────────────────────────────────────────────────┐
│ Name                ┆ Type ┆ Runs                                                   │
╞═════════════════════╪══════╪════════════════════════════════════════════════════════╡
│ rustfmt             ┆ both ┆ rustfmt --edition 2021                                 │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ clippy              ┆ lint ┆ cargo clippy --locked --all-targets --all-features     │
│                     ┆      ┆ --workspace -- -D clippy::all                          │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ prettier            ┆ both ┆ ./node_modules/.bin/prettier --no-config --print-width │
│                     ┆      ┆ 100 --prose-wrap always                                │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ omegasort-gitignore ┆ both ┆ omegasort --sort path --unique                         │
└─────────────────────┴──────┴────────────────────────────────────────────────────────┘

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 once. 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 usually 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.

You can also use the experimental invoke.per-dir-or-once = n option to have precious switch between once and per-dir, depending on the number of directories that precious will operate on.

Quiet Flags for Commands

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 command 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 if there are no errors when tidying, 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 the exit code will not be 0 or 1.

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", working-dir = "dir", and path-args = "none":

include     = "**/*.rs"
invoke      = "per-dir"
working-dir = "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.

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