[codegen][Go] Fix compilation error of generated go code when schema is free form object (#5391)

* Fix code generation for free-form objects in go-experimental

* Execute scripts in bin directory

* Add more use cases for open-ended types

* Add more use cases for open-ended types

* Add more use cases for open-ended types

* add code comments

* Better name for test properties

* handle scenario when type is arbitrary

* handle interface{} scenario

* handle interface{} scenario

* add helper function isAnyType

* isAnyType function

* implementation of isAnyType function

* fix javadoc issue

* handle interface{} scenario

* use equals comparison instead of ==

* merge from master

* Add code documentation

* add code comments, remove unused min/max attribute, fix equals method

* Handle 'anytype' use case

* add code comments

* override postProcessModelProperty to set vendor extension

* Use vendorExtensions.x-golang-is-container

* fix compilation error of generated code

* fix compilation error of generated code

* fix compilation error of generated code

Author: sebastien-rosset

docs/generators/go-experimental.md

@@ -40,6 +40,8 @@ sidebar_label: go-experimental
 <li>int</li>
 <li>int32</li>
 <li>int64</li>
+<li>interface{}</li>
+<li>map[string]interface{}</li>
 <li>rune</li>
 <li>string</li>
 <li>uint</li>

docs/generators/go-gin-server.md

@@ -33,6 +33,8 @@ sidebar_label: go-gin-server
 <li>int</li>
 <li>int32</li>
 <li>int64</li>
+<li>interface{}</li>
+<li>map[string]interface{}</li>
 <li>rune</li>
 <li>string</li>
 <li>uint</li>

docs/generators/go-server.md

@@ -36,6 +36,8 @@ sidebar_label: go-server
 <li>int</li>
 <li>int32</li>
 <li>int64</li>
+<li>interface{}</li>
+<li>map[string]interface{}</li>
 <li>rune</li>
 <li>string</li>
 <li>uint</li>

docs/generators/go.md

@@ -40,6 +40,8 @@ sidebar_label: go
 <li>int</li>
 <li>int32</li>
 <li>int64</li>
+<li>interface{}</li>
+<li>map[string]interface{}</li>
 <li>rune</li>
 <li>string</li>
 <li>uint</li>

modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java

@@ -20,12 +20,43 @@
 import java.util.*;
 
 public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperties {
-    public String openApiType, baseName, complexType, getter, setter, description, dataType,
-            datatypeWithEnum, dataFormat, name, min, max, defaultValue, defaultValueWithParam,
-            baseType, containerType, title;
+    /**
+     * The value of the 'type' attribute in the OpenAPI schema.
+     * The per-language codegen logic may change to a language-specific type.
+     */
+    public String openApiType;
+    public String baseName;
+    public String complexType;
+    public String getter;
+    public String setter;
+    /**
+     * The value of the 'description' attribute in the OpenAPI schema.
+     */
+    public String description;
+    /**
+     * The language-specific data type for this property. For example, the OpenAPI type 'integer'
+     * may be represented as 'int', 'int32', 'Integer', etc, depending on the programming language.
+     */
+    public String dataType;
+    public String datatypeWithEnum;
+    public String dataFormat;
+    /**
+     * The name of this property in the OpenAPI schema.
+     */
+    public String name;
+    public String min; // TODO: is this really used?
+    public String max; // TODO: is this really used?
+    public String defaultValue;
+    public String defaultValueWithParam;
+    public String baseType;
+    public String containerType;
+    /**
+     * The value of the 'title' attribute in the OpenAPI schema.
+     */
+    public String title;
 
     /**
-     * The 'description' string without escape charcters needed by some programming languages/targets
+     * The 'description' string without escape characters needed by some programming languages/targets
      */
     public String unescapedDescription;
 
@@ -47,10 +78,30 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public String example;
 
     public String jsonSchema;
+    /**
+     * The value of the 'minimum' attribute in the OpenAPI schema.
+     * The value of "minimum" MUST be a number, representing an inclusive lower limit for a numeric instance.
+     */
     public String minimum;
+    /**
+     * The value of the 'maximum' attribute in the OpenAPI schema.
+     * The value of "maximum" MUST be a number, representing an inclusive upper limit for a numeric instance.
+     */
     public String maximum;
+    /**
+     * The value of the 'multipleOf' attribute in the OpenAPI schema.
+     * The value of "multipleOf" MUST be a number, strictly greater than 0.
+     */
     public Number multipleOf;
+    /**
+     * The value of the 'exclusiveMinimum' attribute in the OpenAPI schema.
+     * The value of "exclusiveMinimum" MUST be number, representing an exclusive lower limit for a numeric instance.
+     */
     public boolean exclusiveMinimum;
+    /**
+     * The value of the 'exclusiveMaximum' attribute in the OpenAPI schema.
+     * The value of "exclusiveMaximum" MUST be number, representing an exclusive upper limit for a numeric instance.
+     */
     public boolean exclusiveMaximum;
     public boolean hasMore;
     public boolean required;
@@ -59,6 +110,12 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public boolean hasMoreNonReadOnly; // for model constructor, true if next property is not readonly
     public boolean isPrimitiveType;
     public boolean isModel;
+    /**
+     * True if this property is an array of items or a map container.
+     * See:
+     * - ModelUtils.isArraySchema()
+     * - ModelUtils.isMapSchema()
+     */
     public boolean isContainer;
     public boolean isString;
     public boolean isNumeric;
@@ -76,7 +133,15 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public boolean isUuid;
     public boolean isUri;
     public boolean isEmail;
+    /**
+     * The type is a free-form object, i.e. it is a map of string to values with no declared properties
+     */
     public boolean isFreeFormObject;
+    /**
+     * The 'type' in the OAS schema is unspecified (i.e. not set). The value can be number, integer, string, object or array.
+     * If the nullable attribute is set to true, the 'null' value is valid.
+     */
+    public boolean isAnyType;
     public boolean isListContainer;
     public boolean isMapContainer;
     public boolean isEnum;
@@ -621,7 +686,7 @@ public boolean equals(Object o) {
                 exclusiveMaximum == that.exclusiveMaximum &&
                 hasMore == that.hasMore &&
                 required == that.required &&
-                deprecated == this.deprecated &&
+                deprecated == that.deprecated &&
                 secondaryParam == that.secondaryParam &&
                 hasMoreNonReadOnly == that.hasMoreNonReadOnly &&
                 isPrimitiveType == that.isPrimitiveType &&

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -1945,14 +1945,19 @@ private String getPrimitiveType(Schema schema) {
             }
             return "string";
         } else if (ModelUtils.isFreeFormObject(schema)) {
+            // Note: the value of a free-form object cannot be an arbitrary type. Per OAS specification,
+            // it must be a map of string to values.
             return "object";
         } else if (schema.getProperties() != null && !schema.getProperties().isEmpty()) { // having property implies it's a model
             return "object";
         } else if (StringUtils.isNotEmpty(schema.getType())) {
             LOGGER.warn("Unknown type found in the schema: " + schema.getType());
             return schema.getType();
         }
-
+        // The 'type' attribute has not been set in the OAS schema, which means the value
+        // can be an arbitrary type, e.g. integer, string, object, array, number...
+        // TODO: we should return a different value to distinguish between free-form object
+        // and arbitrary type.
         return "object";
     }
 
@@ -2707,6 +2712,9 @@ public CodegenProperty fromProperty(String name, Schema p) {
             setNonArrayMapProperty(property, type);
             Schema refOrCurrent = ModelUtils.getReferencedSchema(this.openAPI, p);
             property.isModel = (ModelUtils.isComposedSchema(refOrCurrent) || ModelUtils.isObjectSchema(refOrCurrent)) && ModelUtils.isModel(refOrCurrent);
+            if (ModelUtils.isAnyTypeSchema(p)) {
+                property.isAnyType = true;
+            }
         }
 
         LOGGER.debug("debugging from property return: " + property);

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java

@@ -91,7 +91,10 @@ public AbstractGoCodegen() {
                         "complex64",
                         "complex128",
                         "rune",
-                        "byte")
+                        "byte",
+                        "map[string]interface{}",
+                        "interface{}"
+                        )
         );
 
         instantiationTypes.clear();
@@ -116,7 +119,17 @@ public AbstractGoCodegen() {
         typeMapping.put("file", "*os.File");
         typeMapping.put("binary", "*os.File");
         typeMapping.put("ByteArray", "string");
+        // A 'type: object' OAS schema without any declared property is
+        // (per JSON schema specification) "an unordered set of properties
+        // mapping a string to an instance".
+        // Hence map[string]interface{} is the proper implementation in golang.
+        // Note: OpenAPITools uses the same token 'object' for free-form objects
+        // and arbitrary types. A free form object is implemented in golang as
+        // map[string]interface{}, whereas an arbitrary type is implemented
+        // in golang as interface{}.
+        // See issue #5387 for more details.
         typeMapping.put("object", "map[string]interface{}");
+        typeMapping.put("interface{}", "interface{}");
 
         numberTypes = new HashSet<String>(
                 Arrays.asList(
@@ -303,6 +316,12 @@ public String toApiFilename(String name) {
         return name;
     }
 
+    /**
+     * Return the golang implementation type for the specified property.
+     * 
+     * @param p the OAS property.
+     * @return the golang implementation type.
+     */
     @Override
     public String getTypeDeclaration(Schema p) {
         if (ModelUtils.isArraySchema(p)) {
@@ -342,6 +361,12 @@ public String getTypeDeclaration(Schema p) {
         return toModelName(openAPIType);
     }
 
+    /**
+     * Return the OpenAPI type for the property.
+     * 
+     * @param p the OAS property.
+     * @return the OpenAPI type.
+     */
     @Override
     public String getSchemaType(Schema p) {
         String openAPIType = super.getSchemaType(p);
@@ -350,6 +375,9 @@ public String getSchemaType(Schema p) {
 
         if (ref != null && !ref.isEmpty()) {
             type = openAPIType;
+        } else if ("object".equals(openAPIType) && ModelUtils.isAnyTypeSchema(p)) {
+            // Arbitrary type. Note this is not the same thing as free-form object.
+            type = "interface{}";
         } else if (typeMapping.containsKey(openAPIType)) {
             type = typeMapping.get(openAPIType);
             if (languageSpecificPrimitives.contains(type))
@@ -556,6 +584,17 @@ private void setExportParameterName(List<CodegenParameter> codegenParameters) {
         }
     }
 
+    @Override
+    public void postProcessModelProperty(CodegenModel model, CodegenProperty property) {
+        // The 'go-experimental/model.mustache' template conditionally generates accessor methods.
+        // For primitive types and custom types (e.g. interface{}, map[string]interface{}...),
+        // the generated code has a wrapper type and a Get() function to access the underlying type.
+        // For containers (e.g. Array, Map), the generated code returns the type directly. 
+        if (property.isContainer || property.isFreeFormObject || property.isAnyType) {
+            property.vendorExtensions.put("x-golang-is-container", true);
+        }
+    }
+
     @Override
     public Map<String, Object> postProcessModels(Map<String, Object> objs) {
         // remove model imports to avoid error

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java

@@ -167,7 +167,8 @@ public Map<String, Object> postProcessModels(Map<String, Object> objs) {
 
                 for (CodegenProperty param : model.vars) {
                     param.vendorExtensions.put("x-go-base-type", param.dataType);
-                    if (!param.isNullable || param.isMapContainer || param.isListContainer) {
+                    if (!param.isNullable || param.isMapContainer || param.isListContainer ||
+                            param.isFreeFormObject || param.isAnyType) {
                         continue;
                     }
                     if (param.isDateTime) {

modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java

@@ -636,7 +636,7 @@ public static boolean isEmailSchema(Schema schema) {
     }
 
     /**
-     * Check to see if the schema is a model with at least one properties
+     * Check to see if the schema is a model with at least one property.
      *
      * @param schema potentially containing a '$ref'
      * @return true if it's a model with at least one properties
@@ -657,6 +657,42 @@ public static boolean isModel(Schema schema) {
         return schema instanceof ComposedSchema;
     }
 
+    /**
+     * Return true if the schema value can be any type, i.e. it can be
+     * the null value, integer, number, string, object or array.
+     * One use case is when the "type" attribute in the OAS schema is unspecified.
+     * 
+     * Examples:
+     *
+     *     arbitraryTypeValue:
+     *       description: This is an arbitrary type schema.
+     *         It is not a free-form object.
+     *         The value can be any type except the 'null' value.
+     *     arbitraryTypeNullableValue:
+     *       description: This is an arbitrary type schema.
+     *         It is not a free-form object.
+     *         The value can be any type, including the 'null' value.
+     *       nullable: true
+     *
+     * @param schema the OAS schema.
+     * @return true if the schema value can be an arbitrary type. 
+     */
+    public static boolean isAnyTypeSchema(Schema schema) {
+        if (schema == null) {
+            once(LOGGER).error("Schema cannot be null in isAnyTypeSchema check");
+            return false;
+        }
+        if (schema.getClass().equals(Schema.class) && schema.get$ref() == null && schema.getType() == null &&
+                (schema.getProperties() == null || schema.getProperties().isEmpty()) &&
+                schema.getAdditionalProperties() == null && schema.getNot() == null &&
+                schema.getEnum() == null) {
+            return true;
+            // If and when type arrays are supported in a future OAS specification,
+            // we could return true if the type array includes all possible JSON schema types.
+        }
+        return false;
+    }
+
     /**
      * Check to see if the schema is a free form object.
      *
@@ -665,6 +701,25 @@ public static boolean isModel(Schema schema) {
      * 2) Is not a composed schema (no anyOf, oneOf, allOf), and
      * 3) additionalproperties is not defined, or additionalproperties: true, or additionalproperties: {}.
      *
+     * Examples:
+     * 
+     * components:
+     *   schemas:
+     *     arbitraryObject:
+     *       type: object
+     *       description: This is a free-form object.
+     *         The value must be a map of strings to values. The value cannot be 'null'.
+     *         It cannot be array, string, integer, number.
+     *     arbitraryNullableObject:
+     *       type: object
+     *       description: This is a free-form object.
+     *         The value must be a map of strings to values. The value can be 'null',
+     *         It cannot be array, string, integer, number.
+     *       nullable: true
+     *     arbitraryTypeValue:
+     *       description: This is NOT a free-form object.
+     *         The value can be any type except the 'null' value.
+     * 
      * @param schema potentially containing a '$ref'
      * @return true if it's a free-form object
      */
@@ -1361,4 +1416,4 @@ public static void syncValidationProperties(Schema schema, IJsonSchemaValidation
             if (maxProperties != null) target.setMaxProperties(maxProperties);
         }
     }
-}
+}