[Fix/Dart2] Resolve an exception with status 204 and no body. (#7647)

* Resolve an exception situation when a remote server returns 204 with no body.

* Only return a value when needed.

* Use HttpStatus codes instead of magic numbers.

* Drop checking for a body as it will consume too much memory.

* Cosmetic changes.

Author: noordawod

modules/openapi-generator/src/main/resources/dart2/api.mustache

@@ -50,16 +50,19 @@ class {{{classname}}} {
     {{/hasMore}}
   {{/allParams}}
   {{#returnType}}Future<Response> {{/returnType}}{{^returnType}}Future {{/returnType}}{{{nickname}}}WithHttpInfo({{#allParams}}{{#required}}{{{dataType}}} {{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}}{{#hasOptionalParams}}{ {{#allParams}}{{^required}}{{{dataType}}} {{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}} }{{/hasOptionalParams}}) async {
+  {{#hasParams}}
     // Verify required params are set.
     {{#allParams}}
       {{#required}}
     if ({{{paramName}}} == null) {
-     throw ApiException(400, 'Missing required param: {{{paramName}}}');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: {{{paramName}}}');
     }
       {{/required}}
     {{/allParams}}
 
-    final path = '{{{path}}}'.replaceAll('{format}', 'json'){{#pathParams}}.replaceAll('{' + '{{{baseName}}}' + '}', {{{paramName}}}.toString()){{/pathParams}};
+  {{/hasParams}}
+    final path = '{{{path}}}'.replaceAll('{format}', 'json'){{#pathParams}}
+      .replaceAll('{' + '{{{baseName}}}' + '}', {{{paramName}}}.toString()){{/pathParams}};
 
     Object postBody{{#bodyParam}} = {{{paramName}}}{{/bodyParam}};
 
@@ -162,31 +165,30 @@ class {{{classname}}} {
   {{/allParams}}
   {{#returnType}}Future<{{{returnType}}}> {{/returnType}}{{^returnType}}Future {{/returnType}}{{{nickname}}}({{#allParams}}{{#required}}{{{dataType}}} {{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}}{{#hasOptionalParams}}{ {{#allParams}}{{^required}}{{{dataType}}} {{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}} }{{/hasOptionalParams}}) async {
     final response = await {{{nickname}}}WithHttpInfo({{#allParams}}{{#required}}{{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}}{{#hasOptionalParams}} {{#allParams}}{{^required}}{{{paramName}}}: {{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/required}}{{/allParams}} {{/hasOptionalParams}});
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
+    {{#returnType}}
+    // When a remote server returns no body with a status of 204, we shall not decode it.
+    // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
+    // FormatException when trying to decode an empty string.
+    if (response.body != null && response.statusCode != HttpStatus.noContent) {
       {{#isListContainer}}
-        {{#returnType}}
       return (apiClient.deserialize(_decodeBodyBytes(response), '{{{returnType}}}') as List)
         .map((item) => item as {{{returnBaseType}}})
         .toList(growable: false);
-        {{/returnType}}
       {{/isListContainer}}
       {{^isListContainer}}
         {{#isMap}}
-          {{#returnType}}
       return {{{returnType}}}.from(apiClient.deserialize(_decodeBodyBytes(response), '{{{returnType}}}'));
-          {{/returnType}}
         {{/isMap}}
         {{^isMap}}
-          {{#returnType}}
       return apiClient.deserialize(_decodeBodyBytes(response), '{{{returnType}}}') as {{{returnType}}};
-          {{/returnType}}
         {{/isMap}}
       {{/isListContainer}}
     }
-    return{{#returnType}} null{{/returnType}};
+    return null;
+    {{/returnType}}
   }
   {{/operation}}
 }

modules/openapi-generator/src/main/resources/dart2/api_client.mustache

@@ -125,16 +125,16 @@ class ApiClient {
         case 'GET': return await _client.get(url, headers: nullableHeaderParams);
       }
     } on SocketException catch (e, trace) {
-      throw ApiException.withInner(400, 'Socket operation failed: $method $path', e, trace);
+      throw ApiException.withInner(HttpStatus.badRequest, 'Socket operation failed: $method $path', e, trace);
     } on TlsException catch (e, trace) {
-      throw ApiException.withInner(400, 'TLS/SSL communication failed: $method $path', e, trace);
+      throw ApiException.withInner(HttpStatus.badRequest, 'TLS/SSL communication failed: $method $path', e, trace);
     } on IOException catch (e, trace) {
-      throw ApiException.withInner(400, 'I/O operation failed: $method $path', e, trace);
+      throw ApiException.withInner(HttpStatus.badRequest, 'I/O operation failed: $method $path', e, trace);
     } on Exception catch (e, trace) {
-      throw ApiException.withInner(400, 'Exception occurred: $method $path', e, trace);
+      throw ApiException.withInner(HttpStatus.badRequest, 'Exception occurred: $method $path', e, trace);
     }
 
-    throw ApiException(400, 'Invalid HTTP operation: $method $path');
+    throw ApiException(HttpStatus.badRequest, 'Invalid HTTP operation: $method $path');
   }
 
   dynamic _deserialize(dynamic value, String targetType, {bool growable}) {
@@ -182,9 +182,9 @@ class ApiClient {
           break;
       }
     } on Exception catch (e, stack) {
-      throw ApiException.withInner(500, 'Exception during deserialization.', e, stack);
+      throw ApiException.withInner(HttpStatus.internalServerError, 'Exception during deserialization.', e, stack);
     }
-    throw ApiException(500, 'Could not find a suitable class for deserialization');
+    throw ApiException(HttpStatus.internalServerError, 'Could not find a suitable class for deserialization');
   }
 
   /// Update query and header parameters based on authentication settings.

modules/openapi-generator/src/main/resources/dart2/api_helper.mustache

@@ -55,7 +55,7 @@ String parameterToString(dynamic value) {
 /// content type. Otherwise, returns the decoded body as decoded by dart:http package.
 String _decodeBodyBytes(Response response) {
   final contentType = response.headers['content-type'];
-  return contentType != null && contentType.contains('application/json')
-    ? utf8.decode(response.bodyBytes)
+  return contentType != null && contentType.toLowerCase().startsWith('application/json')
+    ? response.bodyBytes == null ? null : utf8.decode(response.bodyBytes)
     : response.body;
 }

samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart

@@ -26,7 +26,7 @@ class PetApi {
   Future addPetWithHttpInfo(Pet body) async {
     // Verify required params are set.
     if (body == null) {
-     throw ApiException(400, 'Missing required param: body');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
     final path = '/pet'.replaceAll('{format}', 'json');
@@ -74,12 +74,9 @@ class PetApi {
   ///   Pet object that needs to be added to the store
   Future addPet(Pet body) async {
     final response = await addPetWithHttpInfo(body);
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
-    }
-    return;
   }
 
   /// Deletes a pet
@@ -95,10 +92,11 @@ class PetApi {
   Future deletePetWithHttpInfo(int petId, { String apiKey }) async {
     // Verify required params are set.
     if (petId == null) {
-     throw ApiException(400, 'Missing required param: petId');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'.replaceAll('{format}', 'json').replaceAll('{' + 'petId' + '}', petId.toString());
+    final path = '/pet/{petId}'.replaceAll('{format}', 'json')
+      .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
 
@@ -146,12 +144,9 @@ class PetApi {
   /// * [String] apiKey:
   Future deletePet(int petId, { String apiKey }) async {
     final response = await deletePetWithHttpInfo(petId,  apiKey: apiKey );
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
-    }
-    return;
   }
 
   /// Finds Pets by status
@@ -167,7 +162,7 @@ class PetApi {
   Future<Response> findPetsByStatusWithHttpInfo(List<String> status) async {
     // Verify required params are set.
     if (status == null) {
-     throw ApiException(400, 'Missing required param: status');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: status');
     }
 
     final path = '/pet/findByStatus'.replaceAll('{format}', 'json');
@@ -218,10 +213,13 @@ class PetApi {
   ///   Status values that need to be considered for filter
   Future<List<Pet>> findPetsByStatus(List<String> status) async {
     final response = await findPetsByStatusWithHttpInfo(status);
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
+    // When a remote server returns no body with a status of 204, we shall not decode it.
+    // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
+    // FormatException when trying to decode an empty string.
+    if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
         .map((item) => item as Pet)
         .toList(growable: false);
@@ -242,7 +240,7 @@ class PetApi {
   Future<Response> findPetsByTagsWithHttpInfo(List<String> tags) async {
     // Verify required params are set.
     if (tags == null) {
-     throw ApiException(400, 'Missing required param: tags');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: tags');
     }
 
     final path = '/pet/findByTags'.replaceAll('{format}', 'json');
@@ -293,10 +291,13 @@ class PetApi {
   ///   Tags to filter by
   Future<List<Pet>> findPetsByTags(List<String> tags) async {
     final response = await findPetsByTagsWithHttpInfo(tags);
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
+    // When a remote server returns no body with a status of 204, we shall not decode it.
+    // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
+    // FormatException when trying to decode an empty string.
+    if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
         .map((item) => item as Pet)
         .toList(growable: false);
@@ -317,10 +318,11 @@ class PetApi {
   Future<Response> getPetByIdWithHttpInfo(int petId) async {
     // Verify required params are set.
     if (petId == null) {
-     throw ApiException(400, 'Missing required param: petId');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'.replaceAll('{format}', 'json').replaceAll('{' + 'petId' + '}', petId.toString());
+    final path = '/pet/{petId}'.replaceAll('{format}', 'json')
+      .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
 
@@ -367,10 +369,13 @@ class PetApi {
   ///   ID of pet to return
   Future<Pet> getPetById(int petId) async {
     final response = await getPetByIdWithHttpInfo(petId);
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
+    // When a remote server returns no body with a status of 204, we shall not decode it.
+    // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
+    // FormatException when trying to decode an empty string.
+    if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
     }
     return null;
@@ -387,7 +392,7 @@ class PetApi {
   Future updatePetWithHttpInfo(Pet body) async {
     // Verify required params are set.
     if (body == null) {
-     throw ApiException(400, 'Missing required param: body');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
     final path = '/pet'.replaceAll('{format}', 'json');
@@ -435,12 +440,9 @@ class PetApi {
   ///   Pet object that needs to be added to the store
   Future updatePet(Pet body) async {
     final response = await updatePetWithHttpInfo(body);
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
-    }
-    return;
   }
 
   /// Updates a pet in the store with form data
@@ -460,10 +462,11 @@ class PetApi {
   Future updatePetWithFormWithHttpInfo(int petId, { String name, String status }) async {
     // Verify required params are set.
     if (petId == null) {
-     throw ApiException(400, 'Missing required param: petId');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'.replaceAll('{format}', 'json').replaceAll('{' + 'petId' + '}', petId.toString());
+    final path = '/pet/{petId}'.replaceAll('{format}', 'json')
+      .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
 
@@ -528,12 +531,9 @@ class PetApi {
   ///   Updated status of the pet
   Future updatePetWithForm(int petId, { String name, String status }) async {
     final response = await updatePetWithFormWithHttpInfo(petId,  name: name, status: status );
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
-    }
-    return;
   }
 
   /// uploads an image
@@ -553,10 +553,11 @@ class PetApi {
   Future<Response> uploadFileWithHttpInfo(int petId, { String additionalMetadata, MultipartFile file }) async {
     // Verify required params are set.
     if (petId == null) {
-     throw ApiException(400, 'Missing required param: petId');
+     throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}/uploadImage'.replaceAll('{format}', 'json').replaceAll('{' + 'petId' + '}', petId.toString());
+    final path = '/pet/{petId}/uploadImage'.replaceAll('{format}', 'json')
+      .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
 
@@ -619,10 +620,13 @@ class PetApi {
   ///   file to upload
   Future<ApiResponse> uploadFile(int petId, { String additionalMetadata, MultipartFile file }) async {
     final response = await uploadFileWithHttpInfo(petId,  additionalMetadata: additionalMetadata, file: file );
-    if (response.statusCode >= 400) {
+    if (response.statusCode >= HttpStatus.badRequest) {
       throw ApiException(response.statusCode, _decodeBodyBytes(response));
     }
-    if (response.body != null) {
+    // When a remote server returns no body with a status of 204, we shall not decode it.
+    // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
+    // FormatException when trying to decode an empty string.
+    if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
     }
     return null;