Command-line tool for symlinking directories with reusable source code into the project.

Language-agnostic. Works equally well for C++ and for HTML web-sites.

Reusing code should be simple. If I have the needed code in a directory on a local drive, I just want to include it in the project. Without packaging it as a library for distribution or messing with IDE settings.

My first thought is to create a symlink:

$ ln -s /abc/libs/mylib /abc/project/mylib

Now project sees mylib as a local directory project/mylib. I can edit both project and mylib while working on the project.

But here problems arise:

• Portability. How do I make the symlinks easy to recreate on another machine?
• Recursive local dependencies. How do I include not only mylib, but all the dependencies of mylib, and the dependencies of those dependencies?

The answer is depz. It reduces these tasks to a one-line command.

Get a working Python ≥3.7 and pip. You may also need a computer. Then:

$ pip3 install depz

Make sure that it is installed:

$ depz --help

Upgrade it later:

$ pip3 install depz --upgrade

• Specify dependencies in depz.txt
• Run the command depz

File xxx/depz.txt lists dependencies for xxx:

• /abc/myproject/depz.txt for myproject
• /abc/libs/mylib/depz.txt for mylib

The depz.txt format:

# lines that specify local directory 
# names are LOCAL dependencies
  
/absolute/path/to/mylib1
../libs/mylib2
~/path/mylib3

# lines that cannot be resolved to an existing 
# directory are considered EXTERNAL dependencies
 
requests
numpy

$ cd /abc/myproject
$ depz

This recursively scans /abc/myproject/depz.txt and prints all the found dependencies. Doesn't make any changes to the file system.

$ cd /abc/myproject
$ depz --relink

Removes all the symlinks found in /abc/myproject. Adds new symlinks to the local dependent directories. Prints external dependencies.

When a project depends on local mylib, it means, it also depends on all the dependencies of mylib. So after scanning myproject/depz.txt we will also scan mylib/depz.txt to include its dependencies too.

When we scan /abc/myproject/depz.txt, the paths are relative to /abc/myproject. Then we found a link to mylib and started scanning /abc/mylib/depz.txt. The paths found there are relative to /abc/mylib.

But all the symlinks will go directly into /abc/myproject.

The following examples show how the directories will be linked when running depz for /abc/project:

This is useful for frameworks with strict directory structures such as Flutter.

By default, the list of all external dependencies is simply printed to the terminal like that:

$ depz

Depz file: /abc/myproject/depz.txt
...
External dependencies: pandas numpy requests

The -e argument causes the command to print only the list of dependencies.

$ depz -e line

pandas numpy requests

$ pip3 install $(depz -e line)

$ pip3 install $(depz -e line --relink)

$ depz -e multi

pandas
numpy
requests

$ depz -e multi > requirements.txt