74 - Add diff renderer and improve reporting

[Derpius]

Issue

Resolves #74

Changes

• Repurposed prettyValue into serialiseValue, which recursively prints tables that do not have an overridden tostring
  • This is aligned with Jest
• Added a new renderDiff function which is used to generate a diff between any two values, optionally performing a "deep" recursive diff
• Updated all code using prettyValue to use serialiseValue
• Changed require paths to remove the need for src.lua. in every require()
  • Paths should be changed in any files that would be included in the diff regardless
• Fixed matcher assertions printing the stack trace twice
• Changed the test result error to not colour its message body
  • This allows matchers to colour their own message (needed for renderDiff)
• Changed the expect print to not serialise the values into expect(...).matcherName(...) to avoid duplicating information

Impact

• Significantly improves the user experience of Lest by allowing users to immediately see deep inequalities in tables through the diff
• Improves the reporting for non-deep equality tests to better highlight expected and received values
• All existing test failure messages will change colour from red to white
  • Update matcher messages to colour expected and received #114 to add colours back in
• DevX improved by removing the need to import from src.lua manually, and automatically importing index.lua files when a directory path is given
  • Remove src.lua imports #115 to update remaining imports

Testing

Fairly well covered by automated tests, but should try the following:

• toBe failure messages display serialised expected and received with no table diff rendering
• toEqual failure messages match toBe if one or both values are not a table
• toEqual failure messages for two tables
  • handles cyclic references
  • shows correct expected and received counts for the number of differences
  • correctly chooses whether a value can be added to the table as an array item ({1, 2, 3}), symbol key ({foo = "bar"}) or expression key ({["end"] = "bar"})
  • correctly marks fields as either unchanged, added, removed or changed (added and removed adjacent for same key)
• never.toBe and never.toEqual failure messages always show the serialised expected value in the format Expected: not %s

Helpful Links

API Docs

Project Board

Discord

[yogwoggf]

If @Vurv78 doesn't pick this up later today then I'll probably start a review

[yogwoggf]

LGTM 👍

[yogwoggf]

Just to confirm, this is a boolean coercion right? Looks sort of strange

[Derpius]

Yep, to avoid returning a non-boolean here