Allow model filtering

[followingell]

Issue

• Closes Filter models for the coverage #24:

"Please add options in the CLI to include and exclude models to filter out the checks in some of the models or a path."

Summary

I added the ability to perform compute commands on only a subset of tables by adding a --model-path-filter option. This means that a subset of models can be selected based upon their original_file_path value (taken from the manifest.json artifact).

This functionality means that dbt-coverage can now be used in monolithic dbt projects which contain sub-projects owned by different teams. Before adding model selection functionality, using dbt-coverage would not have been useful/advisable in such a structure because another, unrelated team may decrease the overall coverage, which can then block PR merging (should dbt-coverage have been integrated as part of a CI/CD pipeline for example).

• See example of added functionality from updated README.md below:

$ cd jaffle_shop
$ dbt run  # Materialize models
$ dbt docs generate  # Generate catalog.json and manifest.json
$ dbt-coverage compute doc --cov-report coverage-doc.json --model-path-filter models/staging/  # Compute doc coverage for a subset of tables, print it and write it to coverage-doc.json file

Coverage report
======================================================
jaffle_shop.stg_customers              0/3       0.0%
jaffle_shop.stg_orders                 0/4       0.0%
jaffle_shop.stg_payments               0/4       0.0%
======================================================
Total                                  0/11      0.0%

$ dbt-coverage compute doc --cov-report coverage-doc.json --model-path-filter models/orders.sql --model-path-filter models/staging/  # Compute doc coverage for a subset of tables, print it and write it to coverage-doc.json file

Coverage report
======================================================
jaffle_shop.orders                     0/9       0.0%
jaffle_shop.stg_customers              0/3       0.0%
jaffle_shop.stg_orders                 0/4       0.0%
jaffle_shop.stg_payments               0/4       0.0%
======================================================
Total                                  0/20      0.0%

Note: this is a relatively 'rough' solution and there are likely many improvements that could be made to my code / far more elegant implementations that would achieve the same functionality. Please, feel free to suggest changes!

Testing

• I have tested these changes on dbt's jaffle_shop 'testing project' and have not encountered issues so far.

[followingell]

Just checking, is anyone available to review this please @sweco, @mrshu?

Is there anything that I can add to the PR to make the review process easier for yourselves?

[mrshu]

Thanks for the PR @followingell -- I'll take a closer look at it later today 🙂

[followingell]

@followingell Is there any specific reason for PurePath here as opposed to using Path that has already been in use?

@mrshu Not sure where the above comment has gone(?), regardless responding here rather than via email:

I think this StackOverflow answer sums it up quite nicely. Essentially, PurePath just performs string-like operations whereas Path can also do I/O operations which we don't need here. As such, I chose to utilise the simpler, parent class.

If you'd rather I just use Path then I'm happy to do so.

[mrshu]

Thanks for putting this together @followingell!

In general, this looks rather nicely -- I've only put a couple of comments here and there to see if I understood the whole concept correctly. Once we get those resolved, we can simply merge it in 🙂

Thanks!

[mrshu]

@followingell how would you feel about changing this to table.original_file_path.startswith(path)? I am mostly concerned about the unintended consequences of having say the staging/ and pre-staging/ folders in one's project and as it currently is, I am afraid --model-path-filter staging/ would cover both.

Alternatively, having a regex option would certainly work too 🙂

[followingell]

@mrshu Again, great thoughts r.e. covering both staging/ and pre-staging/ unintentionally when using --model-path-filter staging/ with my previous implementation.

As per your suggestion I have swapped the code to use startswith and had this reflected in the README since this provides as much control as before whilst reducing the potential for unintended inclusions as outlined above.

[followingell]

@mrshu FYI for now I have finished with changes. As such, ready for review 👍

[mrshu]

Thank you for your patience @followingell -- this is very nicely done and I like it quite a bit!

[mrshu]

Thanks again @followingell , this was now released in 0.3.0!