[CT-2322] [Feature] Side-by-side diff when an enforced model contract fails

[dbeatty10]

Is this your first time submitting a feature request?

• I have read the expectations for open source contributors
• I have searched the existing issues, and I could not find an existing issue for this feature
• I am requesting a straightforward extension of existing dbt functionality, rather than a Big Idea better suited to a discussion

Describe the feature

See this Loom starting at 12:50 for context of this feature proposal:
https://www.loom.com/share/f436e5e336e4433695dc63d53ee72fcf?t=770

Two things:

• Update "Contracts are enabled for this model." to "This model has an enforced contract."
• Do a side-by-side diff rather than a stacked listing of column names

Where a preflight check fails for a model contract, could the output look more like this?

Right now, the output looks like this:

snip...

Describe alternatives you've considered

Sometimes the status quo is the way to go ...
... and sometimes it isn't 😉

Who will this benefit?

This will benefit folks that:

• are using enforced model contracts
• there is a mismatch in the contract leading to a preflight failure
• have a model with tons of columns (or even just a few!)

Are you interested in contributing this feature?

No response

Anything else?

No response

[jtcohen6]

This change wants to happen here:

dbt-core/core/dbt/exceptions.py

Lines 2127 to 2141 in a203fe8

	class ContractError(CompilationError):
	def __init__(self, yaml_columns, sql_columns):
	self.yaml_columns = yaml_columns
	self.sql_columns = sql_columns
	super().__init__(msg=self.get_message())
	def get_message(self) -> str:
	msg = (
	"Contracts are enabled for this model. "
	"Please ensure the name, data_type, and number of columns in your `yml` file "
	"match the columns in your SQL file.\n"
	f"Schema File Columns: {self.yaml_columns}\n"
	f"SQL File Columns: {self.sql_columns}"
	)
	return msg

This would also require updating a few tests, which currently expect to see some specific text in the logs. It's definitely worth doing for the UX improvement :)

[kentkr]

Created a PR for this with some questions!