fix: Avoid validating *.tfvars outside of modules (hashicorp#1447)

Author: radeksimko

internal/decoder/decoder.go

@@ -64,7 +64,13 @@ func varsPathContext(mod *state.Module) (*decoder.PathContext, error) {
 		ReferenceOrigins: make(reference.Origins, 0),
 		ReferenceTargets: make(reference.Targets, 0),
 		Files:            make(map[string]*hcl.File),
-		Validators:       varsValidators,
+	}
+
+	if len(mod.ParsedModuleFiles) > 0 {
+		// Only validate if this is actually a module
+		// as we may come across standalone tfvars files
+		// for which we have no context.
+		pathCtx.Validators = varsValidators
 	}
 
 	for _, origin := range mod.VarsRefOrigins {

internal/terraform/module/module_ops_test.go

@@ -1405,3 +1405,52 @@ func TestSchemaVarsValidation_SingleFile(t *testing.T) {
 		t.Fatalf("expected %d diagnostics, %d given", expectedCount, diagsCount)
 	}
 }
+
+func TestSchemaVarsValidation_outsideOfModule(t *testing.T) {
+	ctx := context.Background()
+	ss, err := state.NewStateStore()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testData, err := filepath.Abs("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	modPath := filepath.Join(testData, "standalone-tfvars")
+
+	err = ss.Modules.Add(modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fs := filesystem.NewFilesystem(ss.DocumentStore)
+	ctx = lsctx.WithDocumentContext(ctx, lsctx.Document{})
+	err = ParseModuleConfiguration(ctx, fs, ss.Modules, modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = LoadModuleMetadata(ctx, ss.Modules, modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = ParseVariables(ctx, fs, ss.Modules, modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = SchemaVariablesValidation(ctx, ss.Modules, ss.ProviderSchemas, modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mod, err := ss.Modules.ModuleByPath(modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectedCount := 0
+	diagsCount := mod.VarsDiagnostics[ast.SchemaValidationSource].Count()
+	if diagsCount != expectedCount {
+		t.Fatalf("expected %d diagnostics, %d given", expectedCount, diagsCount)
+	}
+}

internal/terraform/module/testdata/standalone-tfvars/terraform.tfvars

@@ -0,0 +1 @@
+foo = "bar"