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A lightweight dependency manager

Project description

A lightweight dependency manager for managing project dependencies in multiple contexts. The use case driving development is that of distinguishing between development, testing, and production dependencies in a simple and unified way. However, the application is general purpose and can be used in any project requiring the management of dependencies in multiple contexts.

Currently, only dependencies resolved via apt-get and pip are supported. However, support for other dependency types is planned for future releases (see Future Features for more details).


$ pip install depman


usage: depman [-h] [-f <depfile>] [-t <type>] [-o <outfile>] [--no-header]
              <command> [<context>]

A lightweight dependency manager.

positional arguments:
  <command>             'satisfy' satisfies the dependencies specified in
                        <depfile>. 'validate' only validates <depfile> and
                        does not perform any system operations. 'export'
                        exports requirements to a specified file (using -o)
  <context>             The dependency context to perform <command> on

optional arguments:
  -h, --help            show this help message and exit
  -f <depfile>, --depfile <depfile>
                        The requirements file to load
  -t <type>, --type <type>
                        Restrict operations to dependencies of this type
  -o <outfile>, --outfile <outfile>
                        File to write results to
  --no-header           No export header

If not supplied, <depfile> and <context> default to requirements.yml and all, respectively.


Suppose you have the following requirements.yml in your current working directory

    - test

    - libxml2-dev=2.9.1+dfsg1-5+deb8u2
    - libxslt1-dev
    - lxml
    - Sphinx

    - nose
    - coverage

    - gevent:
        version: <=1.0.2
    - texttable
    - six:
        always_upgrade: yes
    - syn>=0.0.10

    - cleanup:
        yatrfile: provisioning_tasks.yml

This file specifies three dependency contexts: dev, test, prod. In general, any top-level key in requirements.yml specifies a dependency context. The one exception to this rule is includes, which defines inclusion relationships between contexts. In this example, the dev context includes the test context. As such, when depman satisfy test is run at the command line, depman will invoke pip to install nose and coverage, if they do not exist on the system. On the other hand, when depman satisfy dev is run at the command line, depman will first invoke apt-get to install libxml1-dev (version 2.9.1+dfsg1-5+deb8u2) and libxslt1-dev and then invoke pip to install lxml, Sphinx, nose, and coverage (in general, apt dependencies are processed before pip dependencies). Because test is “included” in dev, its dependencies are processed whenever dev is processed.

depman also accepts the special context all as a valid command line parameter. Running depman satisfy all causes depman to satisfy the dependencies in all of the defined dependency contexts. In this example, it would cause depman to satisfy the dependencies for dev, test, and prod. Running depman satisfy is equivalent to running depman satisfy all.

Currently, only three dependency types are supported in any context: apt, pip, and yatr. However, support for other dependency types is planned for future releases (see Future Features for more details).

Dependencies are specified in each context under each dependency type as YAML list elements. If the element is a string, the dependency in question will be treated as satisfied if some version of the package denoted by the string exists on the system. For more detailed dependency requirements, the name of the package can be listed as the key to a YAML dictionary of dependency options. This can be seen, for example, in the gevent dependency, in which a version less than of equal to 1.0.2 is specified as a requirement. Additionally, the six package contains the always_upgrade option, which causes depman to always attempt to upgrade the package, regardless of the current version installed.

Package version relations can be specified in various ways. In the prod context, pip is constrained to only install a version of syn that is greater than or equal to 0.0.10. Likewise, in the dev context, apt is constrained to install version 2.9.1+dfsg1-5+deb8u2 of libxml2-dev. And, as seen above, the pip gevent dependency is constrained to a version less than or equal to 1.0.2

The yatr dependency is a special type that will invoke yatr to execute the specified task from the specified yatrfile. In this example, the prod context specifies that a task named cleanup defined in provisioning_tasks.yml is to be run. yatr “dependencies” are not true dependencies, but task invocations, and thus cannot truly be satisfied. As a result, invoking depman to satisfy a yatr dependency will always cause the task defined therein to be executed. By default, yatr tasks will only run after all other dependencies have been satisfied. yatr dependencies can be used to perform scripted installs, cleanup and provisioning actions, and other tasks that are otherwise beyond the scope of a lightweight dependency manager.


Dependencies can also be exported. In this example, running

depman export prod -t pip -o requirements.txt

will produce a file requirements.txt in the current directory that looks like:

# Auto-generated by depman 0.3.3

The header comment can be suppressed by supplying the --no-header option.

Future Features

The following features are planned for future releases:

  • apt PPA support
  • Relative order specification for dependency satisfaction
  • Support for other package managers
  • Support for scripted installs from source

Project details

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