remove the extra logic to detect prov funcs

We can't detect why a provider function is missing is all cases, so
get rid of the extra logic trying to do that.

We also admit here that we need to allow a provider function within a
variable validation condition, because that is not the only way these
could fail during init, and it's otherwise valid during the next phase.

internal/command/init2_test.go

@@ -70,11 +70,7 @@ func TestInit2_dynamicSourceErrors(t *testing.T) {
 			args:      []string{"-get=false", "-var", "module_version=0.0.2"},
 			wantError: "Module version requirements have changed",
 		},
-		"provider function in const variable validation check": {
-			fixture:   "provider-function-in-const-validation",
-			args:      []string{"-var", "module_name=example"},
-			wantError: "This happens if variable validation is\nbeing used on const variables during init.",
-		},
+
 		"const variable with static validation check": {
 			fixture:   "const-var-source-with-validation",
 			args:      []string{"-var", "module_name=nonexistent"},
@@ -176,6 +172,13 @@ func TestInit2_dynamicSourceSuccess(t *testing.T) {
 			// so the value will always be unknown regardless of input.
 			args: []string{"-var", "const_var=hello"},
 		},
+
+		// The validation returns unknown during init, and must wait until
+		// a full validation is actually run.
+		"provider function in const variable validation check": {
+			fixture: "provider-function-in-const-validation",
+			args:    []string{"-var", "module_name=example"},
+		},
 	}
 
 	for name, tc := range tests {

internal/lang/eval.go

@@ -74,7 +74,7 @@ func (s *Scope) EvalBlock(body hcl.Body, schema *configschema.Block) (cty.Value,
 	body = blocktoattr.FixUpBlockAttrs(body, schema)
 
 	val, evalDiags := hcldec.Decode(body, spec, ctx)
-	diags = diags.Append(CheckForUnknownFunctionDiags(evalDiags, s.IgnoreUnknownProviderFunctions, false))
+	diags = diags.Append(CheckForUnknownFunctionDiags(evalDiags, s.IgnoreUnknownProviderFunctions))
 
 	return val, diags
 }
@@ -152,7 +152,7 @@ func (s *Scope) EvalSelfBlock(body hcl.Body, self cty.Value, schema *configschem
 	}
 
 	val, decDiags := hcldec.Decode(body, schema.DecoderSpec(), ctx)
-	diags = diags.Append(CheckForUnknownFunctionDiags(decDiags, s.IgnoreUnknownProviderFunctions, false))
+	diags = diags.Append(CheckForUnknownFunctionDiags(decDiags, s.IgnoreUnknownProviderFunctions))
 	return val, diags
 }
 
@@ -178,7 +178,7 @@ func (s *Scope) EvalExpr(expr hcl.Expression, wantType cty.Type) (cty.Value, tfd
 	}
 
 	val, evalDiags := expr.Value(ctx)
-	diags = diags.Append(CheckForUnknownFunctionDiags(evalDiags, s.IgnoreUnknownProviderFunctions, false))
+	diags = diags.Append(CheckForUnknownFunctionDiags(evalDiags, s.IgnoreUnknownProviderFunctions))
 
 	if wantType != cty.DynamicPseudoType {
 		var convErr error
@@ -523,7 +523,7 @@ func normalizeRefValue(val cty.Value, diags tfdiags.Diagnostics) (cty.Value, tfd
 // namespace. The generic unknown function diagnostic from hcl does not direct
 // the user on how to remedy the situation in Terraform, and we can give more
 // useful information in a few Terraform specific cases here.
-func CheckForUnknownFunctionDiags(diags hcl.Diagnostics, ignoreUnknownProviderFunctions bool, forbidProviderFunctions bool) hcl.Diagnostics {
+func CheckForUnknownFunctionDiags(diags hcl.Diagnostics, ignoreUnknownProviderFunctions bool) hcl.Diagnostics {
 	var filteredDiags hcl.Diagnostics
 	for _, d := range diags {
 		extra, ok := hcl.DiagnosticExtra[hclsyntax.FunctionCallUnknownDiagExtra](d)
@@ -561,25 +561,9 @@ func CheckForUnknownFunctionDiags(diags hcl.Diagnostics, ignoreUnknownProviderFu
 		// just get an unknown value result for any provider function calls, which is fine because
 		// we won't have any provider functions available at this point anyway.
 		if ignoreUnknownProviderFunctions {
-
-			// For situations during init where provider functions could appear but are not valid, we need to keep
-			// the diagnostic, but we also add some info about why the function cannot be used in this context.
-			//
-			// Currently the only expressions that could encounter this situtation are validation blocks on constant variables.
-			if forbidProviderFunctions {
-				d.Detail = fmt.Sprintf("%s The function %q is not available because the provider namespace is "+
-					"not populated in this context. This happens if variable validation is being used on const variables during init. "+
-					"At this time we have neither downloaded nor initialized the provider, hence provider-defined functions are not usable and "+
-					"should be removed from the validation block.",
-					d.Detail, namespace+"::"+name)
-
-				filteredDiags = filteredDiags.Append(d)
-			}
-
 			continue
-		} else {
-			filteredDiags = filteredDiags.Append(d)
 		}
+		filteredDiags = filteredDiags.Append(d)
 
 		// the diagnostic isn't really shared with anything, and copying would
 		// still retain the internal pointers, so we're going to modify the

internal/terraform/eval_variable.go

@@ -333,7 +333,7 @@ func evalVariableValidation(validation *configs.CheckRule, hclCtx *hcl.EvalConte
 	var diags tfdiags.Diagnostics
 
 	result, moreDiags := validation.Condition.Value(hclCtx)
-	diags = diags.Append(lang.CheckForUnknownFunctionDiags(moreDiags, walkOp == walkInit, true))
+	diags = diags.Append(lang.CheckForUnknownFunctionDiags(moreDiags, walkOp == walkInit))
 	errorValue, errorDiags := validation.ErrorMessage.Value(hclCtx)
 
 	// The following error handling is a workaround to preserve backwards