Report & correct duplicate variable definitions across auto-loaded tfvars files

[radeksimko]

Use-cases

Users with more complex modules and many variables may not always notice duplicate entries across multiple autoloaded variable files.

For example, say we have the following variable files with variable definitions:

• alpha.auto.tfvars - one, two
• beta.auto.tfvars - three
• gama.auto.tfvars - one, four

User may not notice the one being declared twice in alpha.auto.tfvars and gama.auto.tfvars until they run terraform validate or plan or similar command.

Attempted Solutions

Manual inspection, or terraform validate.

Proposal

• Report duplicates (across any auto-loaded *.tfvars and *.tfvars.json files) as diagnostics
• Provide code action to remove duplicates (user is given a choice to decide which one to keep)