DecodeReferenceOrigins collects reference origins, using previously parsed AST (via [ParseModuleConfiguration]), core schema of appropriate version (as obtained via [GetTerraformVersion]) and provider schemas ([PreloadEmbeddedSchema] or [ObtainSchema]).

DecodeReferenceTargets collects reference targets, using previously parsed AST (via [ParseModuleConfiguration]), core schema of appropriate version (as obtained via [GetTerraformVersion]) and provider schemas ([PreloadEmbeddedSchema] or [ObtainSchema]).

DecodeWriteOnlyAttributes collects usages of write only attributes, using previously parsed AST (via [ParseModuleConfiguration]), core schema of appropriate version (as obtained via [GetTerraformVersion]) and provider schemas ([PreloadEmbeddedSchema] or [ObtainSchema]).

GetModuleDataFromRegistry obtains data about any modules (inputs & outputs) from the Registry API based on module calls which were previously parsed via [LoadModuleMetadata].

LoadModuleMetadata loads data about the module in a version-independent way that enables us to decode the rest of the configuration, e.g.

ParseModuleConfiguration parses the module configuration, i.e.

PreloadEmbeddedSchema loads provider schemas based on provider requirements parsed earlier via [LoadModuleMetadata].

ReferenceValidation does validation based on (mis)matched reference origins and targets, to flag up "orphaned" references.

SchemaModuleValidation does schema-based validation of module files (*.tf) and produces diagnostics associated with any "invalid" parts of code.

TerraformValidate uses Terraform CLI to run validate subcommand and turn the provided (JSON) output into diagnostics associated with "invalid" parts of code.