# Using leanproject #

## Basic usage #

Everything is done using the leanproject command-line tool. You can use leanproject --help to get the list of available commands and options.

leanproject only supports Lean 3. If you are using Lean 4, the information on this page is not relevant.

### Getting an existing Lean 3 project #

The command to fetch an existing project from GitHub and make sure it includes a copy of mathlib ready to go is leanproject get name where name is either a git url, such as https://github.com/leanprover-community/tutorials.git or git@github.com:leanprover-community/tutorials.git, or a GitHub project identifier such as leanprover-community/tutorials. The organization name defaults to leanprover-community so the simplest way get the tutorials project is to run:

leanproject get tutorials


You can specify a git branch name my_branch by appending :my_branch at the end of the specified name (without space). By default this branch should be an existing branch. Use leanproject get -b project_name:branch_name to get the project project_name and then create a branch branch_name and start working on it. You can also specify a target directory name as a second argument to the command.

### Creating a new project #

You can create a project in a new folder my_project by running:

leanproject new my_project


If you omit the argument, the project will be created directly inside the current folder. This new project will be using the latest version of Lean compatible with mathlib, and include a pre-built mathlib.

### Building a project #

Only mathlib itself comes with pre-built olean files. In order to build oleans in a project (which is needed for every non-trivial project in order to get decent interactive Lean speed), you can use:

leanproject build


### Getting mathlib oleans #

In an existing project depending on mathlib (for mathlib itself, use leanproject get-cache, see below), you can run:

leanproject get-mathlib-cache


to download a compiled mathlib at the commit currently specified in the project leanpkg.toml (see the next section if you want to update this commit and get the latest mathlib).

If you already have an existing project and you want to upgrade it then your can use

leanproject pull


to run git pull and then get mathlib olean files. If the relevant git remote is not called origin then you can indicate its name as in leanproject pull my_remote.

If you have Lean 3 in VS Code open, you should restart Lean by opening the command palette with ctrl+p (cmd+p on macOS) and running the "Lean: Restart server" command.

In an existing project depending on mathlib, you can upgrade to the latest mathlib version by running:

leanproject upgrade-mathlib


This can be abbreviated to leanproject up. By default, this will update the version of Lean 3 used by this project to match the latest version compatible with mathlib. You can forbid such an upgrade by using leanproject --no-lean-upgrade upgrade-mathlib.

Note that when working in a shared repository, after pushing the changes made to leanproject.toml by this command, collaborators will need to run get-mathlib-cache as described above.

If you have Lean 3 in VS Code open, you should restart Lean by opening the command palette with ctrl+p (cmd+p on macOS) and running the "Lean: Restart server" command.

### Adding mathlib to an existing project #

If you already have a Lean project but it doesn't use mathlib yet, you can go to the project folder and run:

leanproject add-mathlib


By default, this will update the version of Lean 3 used by this project to match the latest version compatible with mathlib. You can forbid such an upgrade by using leanproject --no-lean-upgrade add-mathlib.

### Project olean cache #

In any Lean 3 project (including mathlib itself), it can be useful to store and retrieve olean files, especially if the project has several git branches. Storing oleans is done by:

leanproject mk-cache


while retrieving them is done by:

leanproject get-cache


#### Creating caches #

Note that while olean files are indeed the primary target here, mk-cache actually stores everything from the src and test folders of the current project. Since mk-cache uses the current git revision as the key to the cache, it will refuse to run if your repository is dirty.

If the project is mathlib itself, the caches will be stored in $HOME/.mathlib/. Otherwise, they will be stored in a folder _cache inside the project top-level folder. They are named after the corresponding git commit hash. The --force option can be used to overwrite existing cache for the current git revision. Note that the Mathlib github repository will automatically create caches for any commits pushed to it, so it is often unecessary to use mk-cache. #### Retrieving caches # When using get-cache inside the mathlib project, the local cache in $HOME/.mathlib/ will be searched first, before trying to download it. You can force download by running leanproject --force-download get-cache. This --force-download option can also be used with the upgrade-mathlib command.

Frequently a cache is not available for the current commit in a Lean3 project; typically due to new commits having been made on top of the one that a cache was built from. In this situation, get-cache will fail, but show which commits do have available caches:

$leanproject get-cache Looking for my_project oleans for 3b19aed locally... No cache available for revision 3b19aed Looking for my_project oleans for cf40a75 locally... Found local my_project oleans No cache was available for 3b19aed. A cache was found for the ancestor cf40a75. To see the intermediate commits, run: git log --graph 3b19aed cf40a75^! Run leanproject get-cache --rev on one of the available commits above.  In this scenario, running leanproject get-cache --rev cf40a75 will fetch an older cache which will be partially valid. Another option is just to run leanproject get-cache --fallback=download-first which will automatically use the first cache found for a parent commit. If you have Lean 3 in VS Code open, you should restart Lean by opening the command palette with ctrl+p (cmd+p on macOS) and running the "Lean: Restart server" command. ### Import graphs # If you want to generate a graph file showing your project import structure, you can run: leanproject import-graph my_graph_file_name.suffix  where the suffix will determine the output format. It must be either dot or graphml or gexf, (or pdf, svg or png if graphviz is installed). If you want to restrict the graph to files leading to a certain file my_subproject/my_file.lean then you can run: leanproject import-graph --to my_subproject.my_file my_graph_file_name.suffix  Dually, if you want to see all files using my_subproject/my_file.lean then you can run: leanproject import-graph --from my_subproject.my_file my_graph_file_name.suffix  Combining --to and --from is possible. ### Reducing imports # When adding imports to a file incrementally it is easy to end up with a long list of imports where some imports include others transitively. leanproject can be used to print a list of removable imports using the command leanproject reduce-imports lean.module.name  by adding the optional tag --sed a sed script will be produced instead that will remove the unneeded lines for you when the script is executed. Calling this command with no module argument will print removable imports in the entire project. ### Git hooks # If you want leanproject to fetch olean caches after each git checkout, and make olean caches after each git commit in the current project, you can run: leanproject hooks  Beware this will overwrite any post-checkout or post-commit file you might have in your project .git/hooks. ### Cache download url handling # By default, leanproject will try to find mathlib olean files hosted on an Azure server. You permanently override the base url it uses by running: leanproject set-url my_url  so that leanproject will look for caches at my_url/relevant_git_hash.tar.gz. You can override this base url for one invocation using leanproject --from-url my_url ... (where ... denotes a command and its arguments). ### Global mathlib install # If you want to use mathlib outside of a Lean 3 project, you can run: leanproject global-install  This will put a pre-compiled mathlib inside $HOME/.lean, the user-wide Lean project whose dependencies can be used by lean files outside projects. You can upgrade this project using:

leanproject global-upgrade


This is generally discouraged, as this can lead to trouble if you end up working with Lean 3 projects that depend on different versions of Lean 3 / mathlib.

## Troubleshooting #

If leanproject ends with a mysterious error message, you can run it using the --debug flag, e.g. leanproject --debug new my_project. It will then probably output a python trace that you'll be able to paste in a GitHub issue or on Zulip.