This is a prototype for a pip subcommand which compiles a complete set of depended packages and versions from requirements and constraints.

Basically this does exactly the same thing as pip install, but skips actually installing the packages and outputs a list of packages and versions instead.

Furthermore, when -c / --constraint is given, the tool checks that all requirements are actually specified in the constraint list. This gives the user the confirmation that all versions are explicitly specified. One can use constraints without version specifiers to accept any version.

A few extra command line options have been added:

• --flat: Do not recurse into dependencies. This is useful for pinning an explicit list of packages to versions in a constraints file, without resolving any dependencies of packages in the list.
• -o / --output: Path to write a list of pinned dependencies into. Use - for standard output. The list is in a similar format as what pip freeze outputs.
• -j / --json-output: Path to write the JSON format dependency graph of pinned packages into.
• --allow-double: Allow double requirements. This option is only valid together with -c / --constraint. It disregards any version specifiers in given requirements, and allows the same package to be listed multiple times. This is useful when pinning overlapping requirements of multiple packages in one go.

• constraints override requirements. In case the constraint is in conflict with the requirement (e.g. pkg==1.0 vs pkg>=1.1), the constraint wins. Similarly, requirement conflicts are ignored with constraint.

Given the following constraints.txt file:

werkzeug==0.11.11
MarkupSafe==0.23
Jinja2==2.8
Flask==0.11.1

you can run:

$ pip-compile -c /tmp/c.txt -o - Jinja2
Collecting Jinja2==2.8
  Using cached Jinja2-2.8-py2.py3-none-any.whl
Collecting MarkupSafe==0.23 (from Jinja2==2.8)
MarkupSafe==0.23
Jinja2==2.8

or, if you need JSON output:

$ pip-compile -c /tmp/c.txt -j - Jinja2
Collecting Jinja2==2.8
  Using cached Jinja2-2.8-py2.py3-none-any.whl
Collecting MarkupSafe==0.23 (from Jinja2==2.8)
{
    "Jinja2==2.8": [
        "MarkupSafe==0.23"
    ]
}

See pip-compile --help for a full list of command line arguments.