tiktok-sparo/apps/website/docs/pages/guide/sparo_profiles.md
2024-03-01 00:19:27 -08:00

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---
title: Sparo profiles
---
Git's sparse checkout feature normally relies on a collection of glob patterns that are stored in the `.git/info/sparse-checkout` config file. Normal glob syntax proved to be too inefficient, so Git instead uses ["cone mode"](https://git-scm.com/docs/git-sparse-checkout#_internalsnon_cone_problems) that ignores file-matching patterns and only matches directories.
The syntax looks something like this:
**.git/info/sparse-checkout example**
```
/*
!/*/
/apps/
!/apps/*/
/apps/my-app/
!/apps/my-app/*/
/apps/my-app/_/
```
To simplify management, the `git sparse-checkout` command line provides convenient ways to add/remove patterns from this file. However, in a large monorepo with hundreds of projects, managing these globs can be confusing and error-prone.
Sparo's approach is to generate the `.git/info/sparse-checkout` configuration from config files called profiles. This provides many benefits:
- Profiles are specified using [project selectors](https://rushjs.io/pages/developer/selecting_subsets/#--to), for example: _"Give me **app1**, **app2**, and all the projects needed to build them."_ This is more concise and maintainable than specifying globs.
- Profiles are stored in a config file and committed to Git. This makes it easy to share them with your teammates.
- Profiles are automatically updated when switching between branches, which ensures deterministic results. For example, when checking out a very old branch, you want the old profile definition, not today's version of it.
- You combine multiple profiles at the same time (`sparo checkout --profile team1 --profile team2`), which produces the union of their subsets. This is useful for example when modifying a library project that is consumed by projects belonging to several other teams. You could instead use a selector `--from the-library` of course, but it's likely those other teams have included other relevant projects in their profiles.
- Sparo avoids common mistakes by imposing additional restrictions beyond `git sparse-checkout`.
## Best practices for profiles
You an add JSON comments to your profile config files. In a large shared codebase, we recommend adding a standardized header to the top of your files indicating their ownership and purpose. Something like this:
**common/sparo-profiles/example-profile.json**
```js
/**
* OWNER: Customer service team
* PURPOSE: Use this profile when working on the customer service apps.
*/
{
"$schema": "https://tiktok.github.io/sparo/schemas/sparo-profile.schema.json",
/**
* A list of Rush project selectors indicating the project folders to be
* included for sparse checkout. The selectors will be combined to make
* the union superset of projects. See the Rush selector docs for details:
* https://rushjs.io/pages/developer/selecting_subsets/
*/
"selections": [
{
"selector": "--to",
"argument": "tag:cs-dashboard"
},
{
"selector": "--to",
"argument": "tag:cs-tools"
}
]
}
```
## Combining profiles
The simple way to combine profiles is to specify `--profile` multiple times. For example:
```shell
# Check out the union of profiles team-a.json, team-b.json, team-c.json
# NOTE: This will replace whatever profile selection was already checked out.
sparo checkout --profile team-a --profile team-b --profile team-c
```
You can also use `--add-profile` to incrementally combine them. For example:
```shell
# These three commands are equivalent to the above command.
sparo checkout --profile team-a
sparo checkout --add-profile team-b
sparo checkout --add-profile team-c
```
How to checkout NO profile? In other words, returning to the [skeleton](../reference/skeleton_folders.md) state of a clean `sparo clone`? It can't be `sparo checkout`, because if `--profile` is entirely omitted then the existing profile selection is preserved.
```shell
# NOT IMPLEMENTED YET - check out just the skeleton folders
# without applying any profiles
sparo checkout --no-profile
```
## Querying profiles
Engineers can find available profiles in the current branch by invoking the [sparo list-profiles](../commands/sparo_list-profiles) command. The `--project` parameter enables you to query relevant profiles for a given project. For example:
```shell
# Suppose you need to make a fix for the "example-app" project.
# Which sparse checkout profiles include the "example-app" project?
sparo list-profiles --project example-app
# Great, let's add the "example-profile" result to our current checkout
# (combining it with the existing profile).
sparo checkout --add-profile example-profile
```