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On requirements (*-requirements.txt) files
MongoDB requires multiple pypa projects installed to build and test. To that end, we provide our own
*-requirements.txt files for specific domains of use. Inside each requirements file, there are
only include statements for component files. These files are the bare requirements for specific
components of our python environment. This separation allows us to avoid repetition and conflict in
our requirements across components.
For most developers, if you pip-install dev-requirements.txt, you have the python requirements to
lint, build, and test MongoDB.
How to modify a pypa project requirement in a component
The most common edit of our requirements is likely a change to the constraints on a pypa project
that we already use. For example, say that we currently require pymongo >= 3.0, < 3.6.0 in the
component core. You would like to use PyMongo 3.7, so you instead modify the line in
etc/pip/components/core.req to read pymongo >= 3.0, != 3.6.0.
How to add a new component (*.req) file
Occasionally, we will require a set of pypa projects for an entirely new piece of software in our
repository. This usually implies adding a new component file. For example, say that we need to add
a logging system to both local development and evergreen. This system requires the fictional pypa
project FooLog. So we add a file foolog.req and require it from both dev-requirements.txt and
evgtest-requirements.txt. Like the majority of our components, we want it in the toolchain, so we
also add it to toolchain-requirements.txt. The workflow will usually look like:
$ # Make the component file
$ echo "FooLog" >etc/pip/components/foolog.req
$ # Require the component from the requirements files
$ echo "-r components/foolog.req" >>etc/pip/dev-requirements.txt
$ echo "-r components/foolog.req" >>etc/pip/evgtest-requirements.txt
$ echo "-r components/foolog.req" >>etc/pip/toolchain-requirements.txt
How to add a new requirements (*-requirements.txt) file
Rarely, we will have an entirely new domain of requirements that is useful. In this case, we need to
at least make a new requirements file. For example, say we want to make a requirements file for
packaging our code. We would need most of the requirements for dev-requirements.txt but the
testing has already been done in our continuous integration. So we create a new file
package-requirements.txt and require a smaller subset of components. The new file at
etc/pip/package-requirements.txt would look like this:
-r components/platform.req
-r components/core.req
-r components/compile.req
-r components/lint.req