feat: Disruption Diagram - Backend

[jzimbel-mbta]

Asana task: Write the serialization for the line map

The code is split into 5 modules.
I've ordered them below by how the logic generally flows, from public interface down to detailed implementation.

Module	What's in it
DisruptionDiagram	The public interface of all the disruption diagram code.
DisruptionDiagram.Model	Contains high-level logic reflecting Betsy's Miro flowchart.
DisruptionDiagram.Validator	Logic to check that we can build a diagram from this localized alert.
DisruptionDiagram.Builder	Structure used to build the final diagram from a localized alert.
DisruptionDiagram.Label	Logic to determine labels for omitted segments and destination-arrow end slots.

Thoroughly tested! I needed to add some helpers to make writing test scenarios more manageable—those are in test/support/. All tests are against DisruptionDiagram.serialize/1, since it's really the only public interface of all of this code.

• Tests added?

[hannahpurcell]

The one file I haven't fully wrapped my head around is the builder, but I think I'll pick it up through applied work on it. Also @cmaddox5 is helping give it a secondary look, so as long as enough folks on our team can understand it and answer questions about it, then we should be good.

[github-actions]

Coverage of commit 9461d49

Summary coverage rate:
  lines......: 45.2% (2759 of 6098 lines)
  functions..: 44.1% (1121 of 2541 functions)
  branches...: no data found

Files changed coverage rate:
                                                                           |Lines       |Functions  |Branches    
  Filename                                                                 |Rate     Num|Rate    Num|Rate     Num
  ===============================================================================================================
  lib/screens/alerts/alert.ex                                              |25.0%    108|31.1%    45|    -      0
  lib/screens/alerts/informed_entity.ex                                    | 100%      2| 100%     2|    -      0
  lib/screens/alerts/parser.ex                                             |15.3%     59|66.7%    12|    -      0
  lib/screens/route_patterns/route_pattern.ex                              |35.3%     34|21.4%    14|    -      0
  lib/screens/stops/stop.ex                                                |39.8%     83|55.2%    29|    -      0
  lib/screens/v2/disruption_diagram.ex                                     | 100%      1| 100%     1|    -      0
  lib/screens/v2/disruption_diagram/builder.ex                             |95.0%    258|95.6%    45|    -      0
  lib/screens/v2/disruption_diagram/label.ex                               |97.4%     39| 100%     2|    -      0
  lib/screens/v2/disruption_diagram/model.ex                               |92.9%     42|92.3%    13|    -      0
  lib/screens/v2/disruption_diagram/validator.ex                           | 100%     20| 100%     6|    -      0
  lib/screens/v2/localized_alert.ex                                        |82.1%     67|92.3%    13|    -      0
  lib/screens/v2/location_context.ex                                       |66.7%      3|75.0%     4|    -      0
  lib/screens/v2/widget_instance/alert.ex                                  |76.5%     68|92.0%    25|    -      0
  lib/screens/v2/widget_instance/reconstructed_alert.ex                    |88.3%    274|97.1%    35|    -      0
  lib/screens/v2/widget_instance/subway_status.ex                          |92.0%    199|95.1%    41|    -      0
  test/support/disruption_diagram_localized_alert.ex                       |79.1%     43|87.5%     8|    -      0
  test/support/parent_station_id_sigil.ex                                  | 100%      3| 100%     1|    -      0
  test/support/subway_tagged_stop_sequences.ex                             |63.2%     19|61.5%    13|    -      0

Download coverage report

[jzimbel-mbta]

The Back Bay DUP is not loving a change to how its route_pattern logic for alerts is working

This should be fixed now, by this commit. My code previously defaulted to passing filter[canonical]=false, which to my surprise limits the results to only non-canonical route patterns. Definitely not what we want.

[hannahpurcell]

Great! Gave a thumbs-up on two things you suggested. Once those have been applied, I think we're ready to go. Let's merge it and start bug-bashing!! 🐛

[jzimbel-mbta]

I'm not sure why CI stopped running on my commits, but I manually checked and all unit tests are passing, plus Credo and Dialyzer have no complaints. Merging!

edit: Oop nvm, CI is running but the "summary box" at the bottom of the page doesn't say it is. 🤔
I'll give it a few minutes to complete.

[github-actions]

Coverage of commit 2684019

Summary coverage rate:
  lines......: 45.3% (2761 of 6100 lines)
  functions..: 44.1% (1121 of 2541 functions)
  branches...: no data found

Files changed coverage rate:
                                                                           |Lines       |Functions  |Branches    
  Filename                                                                 |Rate     Num|Rate    Num|Rate     Num
  ===============================================================================================================
  lib/screens/alerts/alert.ex                                              |25.0%    108|31.1%    45|    -      0
  lib/screens/alerts/informed_entity.ex                                    | 100%      2| 100%     2|    -      0
  lib/screens/alerts/parser.ex                                             |15.3%     59|66.7%    12|    -      0
  lib/screens/route_patterns/route_pattern.ex                              |35.3%     34|21.4%    14|    -      0
  lib/screens/stops/stop.ex                                                |39.8%     83|55.2%    29|    -      0
  lib/screens/v2/disruption_diagram.ex                                     | 100%      1| 100%     1|    -      0
  lib/screens/v2/disruption_diagram/builder.ex                             |95.0%    260|95.6%    45|    -      0
  lib/screens/v2/disruption_diagram/label.ex                               |97.4%     39| 100%     2|    -      0
  lib/screens/v2/disruption_diagram/model.ex                               |92.9%     42|92.3%    13|    -      0
  lib/screens/v2/disruption_diagram/validator.ex                           | 100%     20| 100%     6|    -      0
  lib/screens/v2/localized_alert.ex                                        |82.1%     67|92.3%    13|    -      0
  lib/screens/v2/location_context.ex                                       |66.7%      3|75.0%     4|    -      0
  lib/screens/v2/widget_instance/alert.ex                                  |76.5%     68|92.0%    25|    -      0
  lib/screens/v2/widget_instance/reconstructed_alert.ex                    |88.3%    274|97.1%    35|    -      0
  lib/screens/v2/widget_instance/subway_status.ex                          |92.0%    199|95.1%    41|    -      0
  test/support/disruption_diagram_localized_alert.ex                       |79.1%     43|87.5%     8|    -      0
  test/support/parent_station_id_sigil.ex                                  | 100%      3| 100%     1|    -      0
  test/support/subway_tagged_stop_sequences.ex                             |63.2%     19|61.5%    13|    -      0

Download coverage report