mirror of
https://github.com/element-hq/synapse
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240 lines
8.5 KiB
Markdown
240 lines
8.5 KiB
Markdown
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# Managing dependencies with Poetry
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This is a quick cheat sheet for developers on how to use [`poetry`](https://python-poetry.org/).
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# Background
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Synapse uses a variety of third-party Python packages to function as a homeserver.
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Some of these are direct dependencies, listed in `pyproject.toml` under the
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`[tool.poetry.dependencies]` section. The rest are transitive dependencies (the
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things that our direct dependencies themselves depend on, and so on recursively.)
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We maintain a locked list of all our dependencies (transitive included) so that
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we can track exactly which version of each dependency appears in a given release.
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See [here](https://github.com/matrix-org/synapse/issues/11537#issue-1074469665)
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for discussion of why we wanted this for Synapse. We chose to use
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[`poetry`](https://python-poetry.org/) to manage this locked list; see
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[this comment](https://github.com/matrix-org/synapse/issues/11537#issuecomment-1015975819)
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for the reasoning.
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The locked dependencies get included in our "self-contained" releases: namely,
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our docker images and our debian packages. We also use the locked dependencies
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in development and our continuous integration.
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Separately, our "broad" dependencies—the version ranges specified in
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`pyproject.toml`—are included as metadata in our "sdists" and "wheels" [uploaded
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to PyPI](https://pypi.org/project/matrix-synapse). Installing from PyPI or from
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the Synapse source tree directly will _not_ use the locked dependencies; instead,
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they'll pull in the latest version of each package available at install time.
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## Example dependency
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An example may help. We have a broad dependency on
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[`phonenumbers`](https://pypi.org/project/phonenumbers/), as declared in
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this snippet from pyproject.toml [as of Synapse 1.57](
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https://github.com/matrix-org/synapse/blob/release-v1.57/pyproject.toml#L133
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):
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```toml
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[tool.poetry.dependencies]
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# ...
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phonenumbers = ">=8.2.0"
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```
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In our lockfile this is
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[pinned]( https://github.com/matrix-org/synapse/blob/dfc7646504cef3e4ff396c36089e1c6f1b1634de/poetry.lock#L679-L685)
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to version 8.12.44, even though
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[newer versions are available](https://pypi.org/project/phonenumbers/#history).
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```toml
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[[package]]
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name = "phonenumbers"
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version = "8.12.44"
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description = "Python version of Google's common library for parsing, formatting, storing and validating international phone numbers."
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category = "main"
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optional = false
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python-versions = "*"
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```
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The lockfile also includes a
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[cryptographic checksum](https://github.com/matrix-org/synapse/blob/release-v1.57/poetry.lock#L2178-L2181)
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of the sdists and wheels provided for this version of `phonenumbers`.
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```toml
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[metadata.files]
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# ...
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phonenumbers = [
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{file = "phonenumbers-8.12.44-py2.py3-none-any.whl", hash = "sha256:cc1299cf37b309ecab6214297663ab86cb3d64ae37fd5b88e904fe7983a874a6"},
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{file = "phonenumbers-8.12.44.tar.gz", hash = "sha256:26cfd0257d1704fe2f88caff2caabb70d16a877b1e65b6aae51f9fbbe10aa8ce"},
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]
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```
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We can see this pinned version inside the docker image for that release:
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```
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$ docker pull matrixdotorg/synapse:v1.57.0
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...
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$ docker run --entrypoint pip matrixdotorg/synapse:v1.57.0 show phonenumbers
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Name: phonenumbers
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Version: 8.12.44
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Summary: Python version of Google's common library for parsing, formatting, storing and validating international phone numbers.
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Home-page: https://github.com/daviddrysdale/python-phonenumbers
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Author: David Drysdale
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Author-email: dmd@lurklurk.org
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License: Apache License 2.0
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Location: /usr/local/lib/python3.9/site-packages
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Requires:
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Required-by: matrix-synapse
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```
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Whereas the wheel metadata just contains the broad dependencies:
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```
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$ cd /tmp
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$ wget https://files.pythonhosted.org/packages/ca/5e/d722d572cc5b3092402b783d6b7185901b444427633bd8a6b00ea0dd41b7/matrix_synapse-1.57.0rc1-py3-none-any.whl
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...
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$ unzip -c matrix_synapse-1.57.0rc1-py3-none-any.whl matrix_synapse-1.57.0rc1.dist-info/METADATA | grep phonenumbers
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Requires-Dist: phonenumbers (>=8.2.0)
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```
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# Tooling recommendation: direnv
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[`direnv`](https://direnv.net/) is a tool for activating environments in your
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shell inside a given directory. Its support for poetry is unofficial (a
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community wiki recipe only), but works solidly in our experience. We thoroughly
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recommend it for daily use. To use it:
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1. [Install `direnv`](https://direnv.net/docs/installation.html) - it's likely
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packaged for your system already.
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2. Teach direnv about poetry. The [shell config here](https://github.com/direnv/direnv/wiki/Python#poetry)
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needs to be added to `~/.config/direnv/direnvrc` (or more generally `$XDG_CONFIG_HOME/direnv/direnvrc`).
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3. Mark the synapse checkout as a poetry project: `echo layout poetry > .envrc`.
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4. Convince yourself that you trust this `.envrc` configuration and project.
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Then formally confirm this to `direnv` by running `direnv allow`.
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Then whenever you navigate to the synapse checkout, you should be able to run
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e.g. `mypy` instead of `poetry run mypy`; `python` instead of
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`poetry run python`; and your shell commands will automatically run in the
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context of poetry's venv, without having to run `poetry shell` beforehand.
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# How do I...
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## ...reset my venv to the locked environment?
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```shell
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poetry install --extras all --remove-untracked
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```
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## ...run a command in the `poetry` virtualenv?
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Use `poetry run cmd args` when you need the python virtualenv context.
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To avoid typing `poetry run` all the time, you can run `poetry shell`
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to start a new shell in the poetry virtualenv context. Within `poetry shell`,
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`python`, `pip`, `mypy`, `trial`, etc. are all run inside the project virtualenv
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and isolated from the rest o the system.
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Roughly speaking, the translation from a traditional virtualenv is:
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- `env/bin/activate` -> `poetry shell`, and
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- `deactivate` -> close the terminal (Ctrl-D, `exit`, etc.)
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See also the direnv recommendation above, which makes `poetry run` and
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`poetry shell` unnecessary.
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## ...inspect the `poetry` virtualenv?
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Some suggestions:
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```shell
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# Current env only
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poetry env info
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# All envs: this allows you to have e.g. a poetry managed venv for Python 3.7,
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# and another for Python 3.10.
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poetry env list --full-path
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poetry run pip list
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```
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Note that `poetry show` describes the abstract *lock file* rather than your
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on-disk environment. With that said, `poetry show --tree` can sometimes be
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useful.
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## ...add a new dependency?
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Either:
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- manually update `pyproject.toml`; then `poetry lock --no-update`; or else
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- `poetry add packagename`. See `poetry add --help`; note the `--dev`,
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`--extras` and `--optional` flags in particular.
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- **NB**: this specifies the new package with a version given by a "caret bound". This won't get forced to its lowest version in the old deps CI job: see [this TODO](https://github.com/matrix-org/synapse/blob/4e1374373857f2f7a911a31c50476342d9070681/.ci/scripts/test_old_deps.sh#L35-L39).
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Include the updated `pyproject.toml` and `poetry.lock` files in your commit.
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## ...remove a dependency?
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This is not done often and is untested, but
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```shell
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poetry remove packagename
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```
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ought to do the trick. Alternatively, manually update `pyproject.toml` and
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`poetry lock --no-update`. Include the updated `pyproject.toml` and poetry.lock`
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files in your commit.
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## ...update the version range for an existing dependency?
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Best done by manually editing `pyproject.toml`, then `poetry lock --no-update`.
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Include the updated `pyproject.toml` and `poetry.lock` in your commit.
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## ...update a dependency in the locked environment?
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Use
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```shell
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poetry update packagename
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```
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to use the latest version of `packagename` in the locked environment, without
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affecting the broad dependencies listed in the wheel.
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There doesn't seem to be a way to do this whilst locking a _specific_ version of
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`packagename`. We can workaround this (crudely) as follows:
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```shell
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poetry add packagename==1.2.3
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# This should update pyproject.lock.
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# Now undo the changes to pyproject.toml. For example
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# git restore pyproject.toml
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# Get poetry to recompute the content-hash of pyproject.toml without changing
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# the locked package versions.
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poetry lock --no-update
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```
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Either way, include the updated `poetry.lock` file in your commit.
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## ...export a `requirements.txt` file?
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```shell
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poetry export --extras all
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```
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Be wary of bugs in `poetry export` and `pip install -r requirements.txt`.
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Note: `poetry export` will be made a plugin in Poetry 1.2. Additional config may
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be required.
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## ...build a test wheel?
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I usually use
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```shell
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poetry run pip install build && poetry run python -m build
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```
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because [`build`](https://github.com/pypa/build) is a standardish tool which
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doesn't require poetry. (It's what we use in CI too). However, you could try
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`poetry build` too.
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