schema: fix unknown value validation bug (#1047)

The validate function should exit early in the case that a value is not
wholly known. This is the intent of the comment and earlier code in this
file - however, subsequent refactors introduced a bug in which one
aspect of validation was run for unknown values: deprecation warnings.

Deprecation warnings for known values are generated by validateType
lower down.

This fix ensures that deprecation warnings are not shown for unknown
values, while still ensuring we exit validation early for all unknown
values.

helper/schema/schema.go

@@ -1735,15 +1735,7 @@ func (m schemaMap) validate(
 	// The SDK has to allow the unknown value through initially, so that
 	// Required fields set via an interpolated value are accepted.
 	if !isWhollyKnown(raw) {
-		if schema.Deprecated != "" {
-			return append(diags, diag.Diagnostic{
-				Severity:      diag.Warning,
-				Summary:       "Argument is deprecated",
-				Detail:        schema.Deprecated,
-				AttributePath: path,
-			})
-		}
-		return diags
+		return nil
 	}
 
 	err = validateConflictingAttributes(k, schema, c)

helper/schema/schema_test.go

@@ -5792,10 +5792,7 @@ func TestSchemaMap_Validate(t *testing.T) {
 			Config: map[string]interface{}{
 				"old_news": hcl2shim.UnknownVariableValue,
 			},
-
-			Warnings: []string{
-				"Warning: Argument is deprecated: please use 'new_news' instead",
-			},
+			Err: false,
 		},
 
 		"Required sub-resource field": {