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fix(go): validate string enum exclusions #25089

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047bc2b
fix(go): validate string enum exclusions
AndreyVMarkelov Oct 1, 2026
026b1dd
chore(go): regenerate samples
AndreyVMarkelov Oct 3, 2026
786b3a5
fix(go): align enum validation with JSON field matching
AndreyVMarkelov Oct 3, 2026
dbafad3
fix(go): validate inherited string enums
AndreyVMarkelov Oct 3, 2026
9d6cec6
fix(go): preserve optional inherited JSON field tags
AndreyVMarkelov Oct 3, 2026
10b5284
fix(go): reuse field tags in flattened enum decoder
AndreyVMarkelov Oct 4, 2026
c958155
fix(go): scope enum validation to affected oneOf models
AndreyVMarkelov Oct 4, 2026
c1b1b92
fix(go): address remaining enum validation review findings
AndreyVMarkelov Oct 5, 2026
a890b52
fix(go): normalize matched alias before required default
AndreyVMarkelov Oct 5, 2026
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138 changes: 138 additions & 0 deletions ...s/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
package org.openapitools.codegen.languages;

import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.TextNode;
import com.google.common.collect.Iterables;
import com.samskivert.mustache.Mustache;
import io.swagger.v3.oas.models.media.Schema;
Expand Down Expand Up @@ -600,6 +601,143 @@ public ModelsMap postProcessModels(ModelsMap objs) {
return objs;
}

@Override

@wing328 wing328 Oct 5, 2026

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suggestion would be nice to add more comments in the new code block (line 606 - 708)

public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs) {
objs = super.postProcessAllModels(objs);
if (!generateUnmarshalJSON) {
return objs;
}

// An allowed enum only needs strict validation when a oneOf sibling excludes values for that property.
Map<CodegenModel, Set<String>> allowedOneOfProperties = new IdentityHashMap<>();
for (ModelsMap models : objs.values()) {
for (ModelMap modelMap : models.getModels()) {
CodegenModel union = modelMap.getModel();
for (String excludedMemberName : union.oneOf) {
CodegenModel excludedMember = ModelUtils.getModelByName(excludedMemberName, objs);
if (excludedMember == null) {
continue;
}
for (CodegenProperty excludedProperty : effectiveVars(excludedMember).values()) {
CodegenProperty not = excludedProperty.getComposedSchemas() == null
? null : excludedProperty.getComposedSchemas().getNot();
if (stringEnumComparison(not, true) == null) {
continue;
}
for (String allowedMemberName : union.oneOf) {
if (allowedMemberName.equals(excludedMemberName)) {
continue;
}
CodegenModel allowedMember = ModelUtils.getModelByName(allowedMemberName, objs);
if (allowedMember == null) {
continue;
}
CodegenProperty allowedProperty = effectiveVars(allowedMember).get(excludedProperty.baseName);
if (stringEnumComparison(allowedProperty, false) != null) {
allowedOneOfProperties.computeIfAbsent(allowedMember, ignored -> new HashSet<>())
.add(excludedProperty.baseName);
}
}
}
}
}
}

for (ModelsMap models : objs.values()) {
for (ModelMap modelMap : models.getModels()) {
CodegenModel model = modelMap.getModel();
if (model.isEnum || hasOneOf(model) || hasAnyOf(model)) {
continue;
}
Map<String, CodegenProperty> effectiveVars = effectiveVars(model);
Map<String, CodegenProperty> ownVars = new HashMap<>();
for (CodegenProperty param : model.vars) {
ownVars.put(param.baseName, param);
}
List<CodegenProperty> validationVars = new ArrayList<>();
boolean hasInheritedStringEnumValidation = false;
for (CodegenProperty param : effectiveVars.values()) {
String allowed = allowedOneOfProperties.getOrDefault(model, Collections.emptySet()).contains(param.baseName)
? stringEnumComparison(param, false) : null;
CodegenProperty not = param.getComposedSchemas() == null ? null : param.getComposedSchemas().getNot();
String excluded = stringEnumComparison(not, true);
if (allowed != null || excluded != null) {
hasInheritedStringEnumValidation |= !ownVars.containsKey(param.baseName);
if (ownVars.containsKey(param.baseName) && ownVars.get(param.baseName).vendorExtensions.containsKey("x-go-datatag")
&& !param.vendorExtensions.containsKey("x-go-datatag")) {
param.vendorExtensions.put("x-go-datatag", ownVars.get(param.baseName).vendorExtensions.get("x-go-datatag"));
}
validationVars.add(param);
param.vendorExtensions.put("x-go-enum-property-name", TextNode.valueOf(param.baseName).toString());
if (allowed != null) {
param.vendorExtensions.put("x-go-allowed-string-enum-comparison", allowed);
if (param.isNullable && (param.isEnumRef || ((List<?>) param.allowableValues.get("values")).contains(null))) {
param.vendorExtensions.put("x-go-allowed-string-enum-null", true);
}
}
if (excluded != null) {
param.vendorExtensions.put("x-go-excluded-string-enum-comparison", excluded);
}
}
}
if (!validationVars.isEmpty()) {
model.vendorExtensions.put("x-go-has-string-enum-validation", true);
model.vendorExtensions.put("x-go-string-enum-validation-vars", validationVars);
List<Map<String, String>> imports = models.getImports();
if (imports.stream().noneMatch(i -> "fmt".equals(i.get("import")))) {
imports.add(createMapping("import", "fmt"));
}
if (model.hasRequired && validationVars.stream().anyMatch(param -> param.required)) {
model.vendorExtensions.put("x-go-enum-required-case-fold", true);
if (imports.stream().noneMatch(i -> "strings".equals(i.get("import")))) {
imports.add(createMapping("import", "strings"));
}
}
imports.sort(Comparator.comparing(i -> i.get("import")));
}
if (hasInheritedStringEnumValidation && !model.isAdditionalPropertiesTrue) {
for (CodegenProperty param : effectiveVars.values()) {
param.vendorExtensions.put("x-go-flattened-json-name", TextNode.valueOf(param.baseName + (param.required ? "" : ",omitempty")).toString());
}
model.vendorExtensions.put("x-go-inherited-string-enum-validation", true);
model.vendorExtensions.put("x-go-flattened-vars", new ArrayList<>(effectiveVars.values()));
}
}
}
return objs;
}

private static Map<String, CodegenProperty> effectiveVars(CodegenModel model) {

@wing328 wing328 Oct 5, 2026

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please add docstrings to newly-created functions effectiveVars, stringEnumComparison

Map<String, CodegenProperty> vars = new LinkedHashMap<>();
for (CodegenProperty param : model.parent == null ? model.vars : model.allVars) {
vars.put(param.baseName, param);
}
return vars;
}

private static String stringEnumComparison(CodegenProperty property, boolean excluded) {
if (property == null || !(property.isString && property.isEnum || property.isEnumRef)
|| property.allowableValues == null
|| !(property.allowableValues.get("values") instanceof List)) {
return null;
}
StringJoiner comparisons = new StringJoiner(excluded ? " || " : " && ");
for (Object value : (List<?>) property.allowableValues.get("values")) {
if (value == null && excluded) {
comparisons.add("value == nil");
continue;
}
if (value == null && property.isNullable) {
continue;
}
if (!(value instanceof String)) {
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return null;
}
comparisons.add("value " + (excluded ? "==" : "!=") + " " + TextNode.valueOf((String) value));
}
return comparisons.length() == 0 ? (property.isNullable && !excluded ? "true" : null) : comparisons.toString();
}

/**
* Prefixes the generated {@code unknown_default_open_api} enum case with the model name when enum class prefixing
* is disabled.
Expand Down
150 changes: 150 additions & 0 deletions modules/openapi-generator/src/main/resources/go/model_simple.mustache
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,89 @@ type _{{{classname}}} {{{classname}}}

{{/hasRequired}}
{{/isAdditionalPropertiesTrue}}
{{#vendorExtensions.x-go-has-string-enum-validation}}
func (o *{{{classname}}}) validateStringEnumValues(data []byte) error {
var fields struct {
{{#vendorExtensions.x-go-string-enum-validation-vars}}
{{name}} json.RawMessage{{#vendorExtensions.x-go-datatag}}{{{.}}}{{/vendorExtensions.x-go-datatag}}{{^vendorExtensions.x-go-datatag}} `json:{{{vendorExtensions.x-go-enum-property-name}}}`{{/vendorExtensions.x-go-datatag}}
{{/vendorExtensions.x-go-string-enum-validation-vars}}
}
if err := json.Unmarshal(data, &fields); err != nil {
return err
}
{{#vendorExtensions.x-go-string-enum-validation-vars}}
{{#vendorExtensions.x-go-allowed-string-enum-comparison}}
if raw := fields.{{name}}; raw != nil {
{{^vendorExtensions.x-go-allowed-string-enum-null}}
if string(raw) == "null" {
return fmt.Errorf("invalid null value for property %s", {{{vendorExtensions.x-go-enum-property-name}}})
}
{{/vendorExtensions.x-go-allowed-string-enum-null}}
var value string
if err := json.Unmarshal(raw, &value); err != nil {
return err
}
if {{#vendorExtensions.x-go-allowed-string-enum-null}}string(raw) != "null" && ({{/vendorExtensions.x-go-allowed-string-enum-null}}{{{vendorExtensions.x-go-allowed-string-enum-comparison}}}{{#vendorExtensions.x-go-allowed-string-enum-null}}){{/vendorExtensions.x-go-allowed-string-enum-null}} {
return fmt.Errorf("invalid value %q for property %s", value, {{{vendorExtensions.x-go-enum-property-name}}})
}
}
{{/vendorExtensions.x-go-allowed-string-enum-comparison}}
{{#vendorExtensions.x-go-excluded-string-enum-comparison}}
if raw := fields.{{name}}; raw != nil {
var value interface{}
if err := json.Unmarshal(raw, &value); err != nil {
return err
}
if {{{vendorExtensions.x-go-excluded-string-enum-comparison}}} {
return fmt.Errorf("excluded value %v for property %s", value, {{{vendorExtensions.x-go-enum-property-name}}})
}
}
{{/vendorExtensions.x-go-excluded-string-enum-comparison}}
{{/vendorExtensions.x-go-string-enum-validation-vars}}
return nil
}

{{^isAdditionalPropertiesTrue}}
{{^hasRequired}}
type _{{{classname}}} {{{classname}}}

func (o *{{{classname}}}) UnmarshalJSON(data []byte) error {
if err := o.validateStringEnumValues(data); err != nil {
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return err
}
{{#vendorExtensions.x-go-inherited-string-enum-validation}}
var decoded struct {
{{#vendorExtensions.x-go-flattened-vars}}
{{^-first}}

{{/-first}}
{{name}} {{^required}}{{^isNullable}}{{^isArray}}{{^isFreeFormObject}}*{{/isFreeFormObject}}{{/isArray}}{{/isNullable}}{{/required}}{{{dataType}}}{{#vendorExtensions.x-go-datatag}}{{{.}}}{{/vendorExtensions.x-go-datatag}}{{^vendorExtensions.x-go-datatag}} `json:{{{vendorExtensions.x-go-flattened-json-name}}}`{{/vendorExtensions.x-go-datatag}}
{{/vendorExtensions.x-go-flattened-vars}}
}
{{#vendorExtensions.x-go-flattened-vars}}
decoded.{{name}} = o.{{name}}
{{/vendorExtensions.x-go-flattened-vars}}
if err := json.Unmarshal(data, &decoded); err != nil {
return err
}
*o = {{{classname}}}{}
{{#vendorExtensions.x-go-flattened-vars}}
o.{{name}} = decoded.{{name}}
{{/vendorExtensions.x-go-flattened-vars}}
{{/vendorExtensions.x-go-inherited-string-enum-validation}}
{{^vendorExtensions.x-go-inherited-string-enum-validation}}
value := _{{{classname}}}(*o)
if err := json.Unmarshal(data, &value); err != nil {
return err
}
*o = {{{classname}}}(value)
{{/vendorExtensions.x-go-inherited-string-enum-validation}}
return nil
}

{{/hasRequired}}
{{/isAdditionalPropertiesTrue}}
{{/vendorExtensions.x-go-has-string-enum-validation}}
// New{{classname}} instantiates a new {{classname}} object
// This constructor will assign default values to properties that have it defined,
// and makes sure properties required by API are set, but the set of arguments
Expand Down Expand Up @@ -360,10 +443,20 @@ func (o {{classname}}) ToMap() (map[string]interface{}, error) {
{{#vendorExtensions.x-go-generate-unmarshal-json}}
{{#isAdditionalPropertiesTrue}}
func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
{{#vendorExtensions.x-go-has-string-enum-validation}}
if err := o.validateStringEnumValues(data); err != nil {
return err
}
{{/vendorExtensions.x-go-has-string-enum-validation}}
{{/isAdditionalPropertiesTrue}}
{{^isAdditionalPropertiesTrue}}
{{#hasRequired}}
func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
{{#vendorExtensions.x-go-has-string-enum-validation}}
if err := o.validateStringEnumValues(data); err != nil {
return err
}
{{/vendorExtensions.x-go-has-string-enum-validation}}
{{/hasRequired}}
{{/isAdditionalPropertiesTrue}}
{{#hasRequired}}
Expand Down Expand Up @@ -398,18 +491,51 @@ func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
return err;
}

{{#vendorExtensions.x-go-enum-required-case-fold}}
lookupRequiredProperty := func(requiredProperty string) (interface{}, string, bool) {
if value, exists := allProperties[requiredProperty]; exists {
return value, requiredProperty, true
}
for name, value := range allProperties {
if strings.EqualFold(name, requiredProperty) {
return value, name, true
}
}
return nil, "", false
}
{{/vendorExtensions.x-go-enum-required-case-fold}}
for _, requiredProperty := range(requiredProperties) {
{{#useDefaultValuesForRequiredVars}}
{{#vendorExtensions.x-go-enum-required-case-fold}}
if value, matchedKey, exists := lookupRequiredProperty(requiredProperty); !exists || value == "" {
{{/vendorExtensions.x-go-enum-required-case-fold}}
{{^vendorExtensions.x-go-enum-required-case-fold}}
if value, exists := allProperties[requiredProperty]; !exists || value == "" {
{{/vendorExtensions.x-go-enum-required-case-fold}}
if _, ok := defaultValueFuncMap[requiredProperty]; ok {
{{#vendorExtensions.x-go-enum-required-case-fold}}
if exists && matchedKey != requiredProperty {
delete(allProperties, matchedKey)
}
{{/vendorExtensions.x-go-enum-required-case-fold}}
allProperties[requiredProperty] = defaultValueFuncMap[requiredProperty]()
defaultValueApplied = true
}
}
{{#vendorExtensions.x-go-enum-required-case-fold}}
if value, _, exists := lookupRequiredProperty(requiredProperty); !exists || value == ""{
{{/vendorExtensions.x-go-enum-required-case-fold}}
{{^vendorExtensions.x-go-enum-required-case-fold}}
if value, exists := allProperties[requiredProperty]; !exists || value == ""{
{{/vendorExtensions.x-go-enum-required-case-fold}}
{{/useDefaultValuesForRequiredVars}}
{{^useDefaultValuesForRequiredVars}}
{{#vendorExtensions.x-go-enum-required-case-fold}}
if _, _, exists := lookupRequiredProperty(requiredProperty); !exists {
{{/vendorExtensions.x-go-enum-required-case-fold}}
{{^vendorExtensions.x-go-enum-required-case-fold}}
if _, exists := allProperties[requiredProperty]; !exists {
{{/vendorExtensions.x-go-enum-required-case-fold}}
{{/useDefaultValuesForRequiredVars}}
return fmt.Errorf("no value given for required property %v", requiredProperty)
}
Expand Down Expand Up @@ -545,6 +671,29 @@ func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
{{/isAdditionalPropertiesTrue}}
{{^isAdditionalPropertiesTrue}}
{{#hasRequired}}
{{#vendorExtensions.x-go-inherited-string-enum-validation}}
var decoded struct {
{{#vendorExtensions.x-go-flattened-vars}}
{{^-first}}

{{/-first}}
{{name}} {{^required}}{{^isNullable}}{{^isArray}}{{^isFreeFormObject}}*{{/isFreeFormObject}}{{/isArray}}{{/isNullable}}{{/required}}{{{dataType}}}{{#vendorExtensions.x-go-datatag}}{{{.}}}{{/vendorExtensions.x-go-datatag}}{{^vendorExtensions.x-go-datatag}} `json:{{{vendorExtensions.x-go-flattened-json-name}}}`{{/vendorExtensions.x-go-datatag}}
{{/vendorExtensions.x-go-flattened-vars}}
}

decoder := json.NewDecoder(bytes.NewReader(data))
decoder.DisallowUnknownFields()
if err = decoder.Decode(&decoded); err != nil {
return err
}

*o = {{{classname}}}{}
{{#vendorExtensions.x-go-flattened-vars}}
o.{{name}} = decoded.{{name}}
{{/vendorExtensions.x-go-flattened-vars}}
return nil
{{/vendorExtensions.x-go-inherited-string-enum-validation}}
{{^vendorExtensions.x-go-inherited-string-enum-validation}}
var{{{classname}}} := _{{{classname}}}{}

decoder := json.NewDecoder(bytes.NewReader(data))
Expand All @@ -558,6 +707,7 @@ func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
*o = {{{classname}}}(var{{{classname}}})

return err
{{/vendorExtensions.x-go-inherited-string-enum-validation}}
}

{{/hasRequired}}
Expand Down
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