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# README
The `count-deps` executable is used in the test-suite to detect when
the number of dependencies of certain modules change ([this blog
post](https://blog.shaynefletcher.org/2020/10/ghc-lib-parser-module-count.html)
gives one example of where and why this can be useful).
More generally it's useful for obtaining insight into a modules'
dependency graph. As used in the tests it produces (1) a count of a
modules' dependencies together with the list of depended upon modules
. However, it can also (2), print a modules' dependency graph in dot
language syntax suitable for rendering with "graphviz" (open source
graph visualization software).
## Installing graphviz
To render graphs generated by `count-deps`, first visit [the graphviz
downloads page](https://graphviz.org/download/) to download and
install graphviz on your system.
## `count-deps` usage examples:
- `make`:
(1) ``inplace/bin/count-deps `inplace/bin/ghc-stage2 --print-libdir` "GHC.Parser"``
(2) ``inplace/bin/count-deps `inplace/bin/ghc-stage2 --print-libdir` "GHC.Parser" --dot``
- `hadrian`:
(1) ``_build/stage1/bin/count-deps `_build/stage1/bin/ghc --print-libdir` "GHC.Parser"``
(2) ``_build/stage1/bin/count-deps `_build/stage1/bin/ghc --print-libdir` "GHC.Parser" --dot``
## Rendering dependency graphs
To render a graph obtained using a type (2) command:
- Copy the output to a file ('`deps.dot`' say)
- Render it with a command like (preprocess with `tred` to remove
edges implied by transitivity)
```bash
tred deps.dot > deps-tred.dot&& dot -Tpdf -o deps.pdf deps-tred.dot
```
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