Support for provider for_each

[apparentlymart]

Language Server Version

n/a (not released yet)

Problem Statement

We'd like to ensure that the following new features are not incorrectly presented as errors and, ideally, support code completion and other features for them:

• for_each argument inside a provider block. This currently supports only early evaluation, but since we plan to offer fully-dynamic support here before too long it might make sense to just implement code completion as normal expressions in the language server to avoid throwaway work.
• provider argument in a resource/data block now supports dynamic instance keys, like aws.by_region["us-west-2"] or aws.by_region[each.key].
• providers argument in a module block now also supports dynamic instance keys on the right-hand side of each element, using the same syntax as in the previous point.

Attempted Solutions

n/a

Proposal

Ideally support code completion and other such mechanisms for these new language features, but at the very least make sure that none of the new features are flagged as errors when used correctly.

Related LSP methods

• textDocument/completion for the new arguments and their expressions
• Possibly textDocument/definition for jumping from a provider reference in a provider/providers argument to the associated provider block, although that's not really for_each-specific so perhaps out of scope.

References

This was one of the deferred tasks from opentofu/opentofu#2123.

Help Wanted

• I'm interested in contributing a fix myself

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