OpenAPITools · wing328 · Jan 13, 2026 · Jan 12, 2026 · Jan 12, 2026 · Jan 12, 2026
diff --git a/bin/configs/rust-reqwest-multipart-async.yaml b/bin/configs/rust-reqwest-multipart-async.yaml
@@ -0,0 +1,9 @@
+generatorName: rust
+outputDir: samples/client/others/rust/reqwest/multipart-async
+library: reqwest
+inputSpec: modules/openapi-generator/src/test/resources/3_0/rust/multipart-file-upload.yaml
+templateDir: modules/openapi-generator/src/main/resources/rust
+additionalProperties:
+  supportAsync: true
+  useSingleRequestParameter: true
+  packageName: multipart-upload-reqwest-async
diff --git a/...openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java b/...openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java
@@ -368,6 +368,45 @@ public ModelsMap postProcessModels(ModelsMap objs) {
                     break;
                 }
             }
+
+            // Compute documentation type for each property
+            // This matches the actual generated code type, including HashSet for uniqueItems
+            for (CodegenProperty cp : cm.vars) {
+                String docType;
+
+                if (cp.datatypeWithEnum != null && !cp.datatypeWithEnum.isEmpty()) {
+                    // Use enum type if available (e.g., Vec<UniqueItemArray> instead of Vec<String>)
+                    docType = cp.datatypeWithEnum;
+                } else {
+                    // Use regular dataType
+                    docType = cp.dataType;
+                }
+
+                // Apply uniqueItems logic (matching model.mustache lines 139, 161)
+                // Arrays with uniqueItems=true use HashSet instead of Vec in the generated code
+                if (Boolean.TRUE.equals(cp.getUniqueItems()) && docType.startsWith("Vec<")) {
+                    docType = docType.replace("Vec<", "HashSet<");
+                }
+
+                cp.vendorExtensions.put("x-doc-type", docType);
+
+                // Determine if this type should have a doc link
+                // Only local models should link, not external types from std lib or crates
+                boolean shouldLink = false;
+                if (cp.complexType != null && !cp.complexType.isEmpty()) {
+                    // Check if it's an external type by looking for known prefixes
+                    String[] externalPrefixes = {"std::", "serde_json::", "uuid::", "chrono::", "url::"};
+                    boolean isExternal = false;
+                    for (String prefix : externalPrefixes) {
+                        if (cp.complexType.startsWith(prefix)) {
+                            isExternal = true;
+                            break;
+                        }
+                    }
+                    shouldLink = !isExternal;
+                }
+                cp.vendorExtensions.put("x-should-link", shouldLink);
+            }
         }
         // process enum in models
         return postProcessModelsEnum(objs);
@@ -741,7 +780,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
             }
 
             // If we use a file body parameter, we need to include the imports and crates for it
-            // But they should be added only once per file 
+            // But they should be added only once per file
             for (var param: operation.bodyParams) {
                 if (param.isFile && supportAsync && !useAsyncFileStream) {
                     useAsyncFileStream = true;
@@ -751,6 +790,18 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
                 }
             }
 
+            // Also check form params for file uploads (multipart)
+            if (!useAsyncFileStream) {
+                for (var param: operation.formParams) {
+                    if (param.isFile && supportAsync) {
+                        useAsyncFileStream = true;
+                        additionalProperties.put("useAsyncFileStream", Boolean.TRUE);
+                        operation.vendorExtensions.put("useAsyncFileStream", Boolean.TRUE);
+                        break;
+                    }
+                }
+            }
+
             // http method verb conversion, depending on client library (e.g. Hyper: PUT => Put, Reqwest: PUT => put)
             if (HYPER_LIBRARY.equals(getLibrary())) {
                 operation.httpMethod = StringUtils.camelize(operation.httpMethod.toLowerCase(Locale.ROOT));

diff --git a/modules/openapi-generator/src/main/resources/rust/api_doc.mustache b/modules/openapi-generator/src/main/resources/rust/api_doc.mustache
@@ -25,7 +25,7 @@ Method | HTTP request | Description
 Name | Type | Description  | Required | Notes
 ------------- | ------------- | ------------- | ------------- | -------------{{/-last}}{{/allParams}}
 {{#allParams}}
-**{{{paramName}}}** | {{^required}}Option<{{/required}}{{#required}}{{#isNullable}}Option<{{/isNullable}}{{/required}}{{#isPrimitiveType}}**{{{dataType}}}**{{/isPrimitiveType}}{{^isPrimitiveType}}[**{{{dataType}}}**]({{{baseType}}}.md){{/isPrimitiveType}}{{^required}}>{{/required}}{{#required}}{{#isNullable}}>{{/isNullable}}{{/required}} | {{{description}}} | {{#required}}[required]{{/required}} |{{#defaultValue}}[default to {{{.}}}]{{/defaultValue}}
+**{{{paramName}}}** | {{^required}}Option<{{/required}}{{#required}}{{#isNullable}}Option<{{/isNullable}}{{/required}}{{#isPrimitiveType}}**{{{dataType}}}**{{/isPrimitiveType}}{{^isPrimitiveType}}{{#complexType}}[**{{{dataType}}}**]({{#lambda.pascalcase}}{{{complexType}}}{{/lambda.pascalcase}}.md){{/complexType}}{{^complexType}}[**{{{dataType}}}**]({{#lambda.pascalcase}}{{{dataType}}}{{/lambda.pascalcase}}.md){{/complexType}}{{/isPrimitiveType}}{{^required}}>{{/required}}{{#required}}{{#isNullable}}>{{/isNullable}}{{/required}} | {{{description}}}{{#isInnerEnum}} (enum: {{#allowableValues}}{{#values}}{{{.}}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}){{/isInnerEnum}} | {{#required}}[required]{{/required}} |{{#defaultValue}}[default to {{{.}}}]{{/defaultValue}}
 {{/allParams}}
 
 ### Return type

diff --git a/modules/openapi-generator/src/main/resources/rust/hyper/api.mustache b/modules/openapi-generator/src/main/resources/rust/hyper/api.mustache
@@ -78,10 +78,25 @@ impl<C: Connect>{{{classname}}} for {{{classname}}}Client<C>
             let query_value = s.iter().map(|s| s.to_string()).collect::<Vec<String>>().join(",");
             {{/isArray}}
             {{^isArray}}
+            {{#isPrimitiveType}}
+            let query_value = s.to_string();
+            {{/isPrimitiveType}}
+            {{^isPrimitiveType}}
+            {{#isEnum}}
+            let query_value = s.to_string();
+            {{/isEnum}}
+            {{^isEnum}}
+            {{#isEnumRef}}
+            let query_value = s.to_string();
+            {{/isEnumRef}}
+            {{^isEnumRef}}
             let query_value = match serde_json::to_string(s) {
                 Ok(value) => value,
                 Err(e) => return Box::pin(futures::future::err(Error::Serde(e))),
             };
+            {{/isEnumRef}}
+            {{/isEnum}}
+            {{/isPrimitiveType}}
             {{/isArray}}
             req = req.with_query_param("{{{baseName}}}".to_string(), query_value);
         }

diff --git a/modules/openapi-generator/src/main/resources/rust/hyper0x/api.mustache b/modules/openapi-generator/src/main/resources/rust/hyper0x/api.mustache
@@ -77,10 +77,25 @@ impl<C: hyper::client::connect::Connect>{{{classname}}} for {{{classname}}}Clien
             let query_value = s.iter().map(|s| s.to_string()).collect::<Vec<String>>().join(",");
             {{/isArray}}
             {{^isArray}}
+            {{#isPrimitiveType}}
+            let query_value = s.to_string();
+            {{/isPrimitiveType}}
+            {{^isPrimitiveType}}
+            {{#isEnum}}
+            let query_value = s.to_string();
+            {{/isEnum}}
+            {{^isEnum}}
+            {{#isEnumRef}}
+            let query_value = s.to_string();
+            {{/isEnumRef}}
+            {{^isEnumRef}}
             let query_value = match serde_json::to_string(s) {
                 Ok(value) => value,
                 Err(e) => return Box::pin(futures::future::err(Error::Serde(e))),
             };
+            {{/isEnumRef}}
+            {{/isEnum}}
+            {{/isPrimitiveType}}
             {{/isArray}}
             req = req.with_query_param("{{{baseName}}}".to_string(), query_value);
         }

diff --git a/modules/openapi-generator/src/main/resources/rust/model.mustache b/modules/openapi-generator/src/main/resources/rust/model.mustache
@@ -167,7 +167,7 @@ impl {{{classname}}} {
     }}{{^-last}}, {{/-last}}{{/requiredVars}}) -> {{{classname}}} {
         {{{classname}}} {
             {{#vars}}
-            {{{name}}}{{^required}}: None{{/required}}{{#required}}{{#isModel}}{{^avoidBoxedModels}}: {{^isNullable}}Box::new({{{name}}}){{/isNullable}}{{#isNullable}}if let Some(x) = {{{name}}} {Some(Box::new(x))} else {None}{{/isNullable}}{{/avoidBoxedModels}}{{/isModel}}{{/required}},
+            {{{name}}}{{^required}}: None{{/required}}{{#required}}{{^isEnum}}{{#isModel}}{{^avoidBoxedModels}}: {{^isNullable}}Box::new({{{name}}}){{/isNullable}}{{#isNullable}}if let Some(x) = {{{name}}} {Some(Box::new(x))} else {None}{{/isNullable}}{{/avoidBoxedModels}}{{/isModel}}{{/isEnum}}{{/required}},
             {{/vars}}
         }
     }

diff --git a/modules/openapi-generator/src/main/resources/rust/model_doc.mustache b/modules/openapi-generator/src/main/resources/rust/model_doc.mustache
@@ -22,7 +22,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-{{#vars}}**{{{name}}}** | {{^required}}Option<{{/required}}{{#required}}{{#isNullable}}Option<{{/isNullable}}{{/required}}{{#isPrimitiveType}}**{{{dataType}}}**{{/isPrimitiveType}}{{^isPrimitiveType}}[**{{{dataType}}}**]({{{complexType}}}.md){{/isPrimitiveType}}{{^required}}>{{/required}}{{#required}}{{#isNullable}}>{{/isNullable}}{{/required}} | {{{description}}} | {{^required}}[optional]{{/required}}{{#isReadOnly}}[readonly]{{/isReadOnly}}{{#defaultValue}}[default to {{{.}}}]{{/defaultValue}}
+{{#vars}}**{{{name}}}** | {{^required}}Option<{{/required}}{{#required}}{{#isNullable}}Option<{{/isNullable}}{{/required}}{{#vendorExtensions.x-should-link}}[**{{{vendorExtensions.x-doc-type}}}**]({{#lambda.pascalcase}}{{{complexType}}}{{/lambda.pascalcase}}.md){{/vendorExtensions.x-should-link}}{{^vendorExtensions.x-should-link}}**{{{vendorExtensions.x-doc-type}}}**{{/vendorExtensions.x-should-link}}{{^required}}>{{/required}}{{#required}}{{#isNullable}}>{{/isNullable}}{{/required}} | {{{description}}}{{#isInnerEnum}} (enum: {{#allowableValues}}{{#values}}{{{.}}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}){{/isInnerEnum}} | {{^required}}[optional]{{/required}}{{#isReadOnly}}[readonly]{{/isReadOnly}}{{#defaultValue}}[default to {{{.}}}]{{/defaultValue}}
 {{/vars}}
 {{/x-mapped-models}}
 {{/vendorExtensions}}
@@ -35,7 +35,7 @@ Name | Type | Description | Notes
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-{{#vars}}**{{{name}}}** | {{^required}}Option<{{/required}}{{#required}}{{#isNullable}}Option<{{/isNullable}}{{/required}}{{#isPrimitiveType}}**{{{dataType}}}**{{/isPrimitiveType}}{{^isPrimitiveType}}[**{{{dataType}}}**]({{{complexType}}}.md){{/isPrimitiveType}}{{^required}}>{{/required}}{{#required}}{{#isNullable}}>{{/isNullable}}{{/required}} | {{{description}}} | {{^required}}[optional]{{/required}}{{#isReadOnly}}[readonly]{{/isReadOnly}}{{#defaultValue}}[default to {{{.}}}]{{/defaultValue}}
+{{#vars}}**{{{name}}}** | {{^required}}Option<{{/required}}{{#required}}{{#isNullable}}Option<{{/isNullable}}{{/required}}{{#vendorExtensions.x-should-link}}[**{{{vendorExtensions.x-doc-type}}}**]({{#lambda.pascalcase}}{{{complexType}}}{{/lambda.pascalcase}}.md){{/vendorExtensions.x-should-link}}{{^vendorExtensions.x-should-link}}**{{{vendorExtensions.x-doc-type}}}**{{/vendorExtensions.x-should-link}}{{^required}}>{{/required}}{{#required}}{{#isNullable}}>{{/isNullable}}{{/required}} | {{{description}}}{{#isInnerEnum}} (enum: {{#allowableValues}}{{#values}}{{{.}}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}){{/isInnerEnum}} | {{^required}}[optional]{{/required}}{{#isReadOnly}}[readonly]{{/isReadOnly}}{{#defaultValue}}[default to {{{.}}}]{{/defaultValue}}
 {{/vars}}
 {{/oneOf.isEmpty}}
 {{^oneOf.isEmpty}}

diff --git a/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache b/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache
@@ -204,6 +204,7 @@ pub {{#supportAsync}}async {{/supportAsync}}fn {{{operationId}}}(configuration:
     {{^isObject}}
     {{^isModel}}
     {{^isEnum}}
+    {{^isEnumRef}}
     {{#isPrimitiveType}}
     if let Some(ref param_value) = {{{vendorExtensions.x-rust-param-identifier}}} {
         req_builder = req_builder.query(&[("{{{baseName}}}", &param_value.to_string())]);
@@ -214,7 +215,18 @@ pub {{#supportAsync}}async {{/supportAsync}}fn {{{operationId}}}(configuration:
         req_builder = req_builder.query(&[("{{{baseName}}}", &serde_json::to_string(param_value)?)]);
     };
     {{/isPrimitiveType}}
+    {{/isEnumRef}}
     {{/isEnum}}
+    {{#isEnum}}
+    if let Some(ref param_value) = {{{vendorExtensions.x-rust-param-identifier}}} {
+        req_builder = req_builder.query(&[("{{{baseName}}}", &param_value.to_string())]);
+    };
+    {{/isEnum}}
+    {{#isEnumRef}}
+    if let Some(ref param_value) = {{{vendorExtensions.x-rust-param-identifier}}} {
+        req_builder = req_builder.query(&[("{{{baseName}}}", &param_value.to_string())]);
+    };
+    {{/isEnumRef}}
     {{/isModel}}
     {{/isObject}}
     {{/isNullable}}
@@ -255,17 +267,22 @@ pub {{#supportAsync}}async {{/supportAsync}}fn {{{operationId}}}(configuration:
         req_builder = req_builder.query(&[("{{{baseName}}}", &serde_json::to_string(param_value)?)]);
         {{/isModel}}
         {{#isEnum}}
-        req_builder = req_builder.query(&[("{{{baseName}}}", &serde_json::to_string(param_value)?)]);
+        req_builder = req_builder.query(&[("{{{baseName}}}", &param_value.to_string())]);
         {{/isEnum}}
+        {{#isEnumRef}}
+        req_builder = req_builder.query(&[("{{{baseName}}}", &param_value.to_string())]);
+        {{/isEnumRef}}
         {{^isObject}}
         {{^isModel}}
         {{^isEnum}}
+        {{^isEnumRef}}
         {{#isPrimitiveType}}
         req_builder = req_builder.query(&[("{{{baseName}}}", &param_value.to_string())]);
         {{/isPrimitiveType}}
         {{^isPrimitiveType}}
         req_builder = req_builder.query(&[("{{{baseName}}}", &serde_json::to_string(param_value)?)]);
         {{/isPrimitiveType}}
+        {{/isEnumRef}}
         {{/isEnum}}
         {{/isModel}}
         {{/isObject}}
@@ -405,11 +422,19 @@ pub {{#supportAsync}}async {{/supportAsync}}fn {{{operationId}}}(configuration:
     {{#supportAsync}}
     {{^required}}
     if let Some(ref param_value) = {{{vendorExtensions.x-rust-param-identifier}}} {
-       multipart_form = multipart_form.file("{{{baseName}}}", param_value.as_os_str()).await?;
+        let file = TokioFile::open(param_value).await?;
+        let stream = FramedRead::new(file, BytesCodec::new());
+        let file_name = param_value.file_name().map(|n| n.to_string_lossy().to_string()).unwrap_or_default();
+        let file_part = reqwest::multipart::Part::stream(reqwest::Body::wrap_stream(stream)).file_name(file_name);
+        multipart_form = multipart_form.part("{{{baseName}}}", file_part);
     }
     {{/required}}
     {{#required}}
-    multipart_form = multipart_form.file("{{{baseName}}}", {{{vendorExtensions.x-rust-param-identifier}}}.as_os_str()).await?;
+    let file = TokioFile::open(&{{{vendorExtensions.x-rust-param-identifier}}}).await?;
+    let stream = FramedRead::new(file, BytesCodec::new());
+    let file_name = {{{vendorExtensions.x-rust-param-identifier}}}.file_name().map(|n| n.to_string_lossy().to_string()).unwrap_or_default();
+    let file_part = reqwest::multipart::Part::stream(reqwest::Body::wrap_stream(stream)).file_name(file_name);
+    multipart_form = multipart_form.part("{{{baseName}}}", file_part);
     {{/required}}
     {{/supportAsync}}
     {{/isFile}}

diff --git a/modules/openapi-generator/src/test/resources/3_0/rust/multipart-file-upload.yaml b/modules/openapi-generator/src/test/resources/3_0/rust/multipart-file-upload.yaml
@@ -0,0 +1,123 @@
+openapi: 3.0.3
+info:
+  title: Multipart File Upload Test
+  description: Regression test for async multipart file uploads with tokio::fs
+  version: 1.0.0
+servers:
+  - url: http://localhost:8080
+paths:
+  /upload/single:
+    post:
+      operationId: uploadSingleFile
+      summary: Upload a single file (required parameter)
+      description: Tests async multipart file upload with required file parameter
+      requestBody:
+        required: true
+        content:
+          multipart/form-data:
+            schema:
+              type: object
+              required:
+                - file
+                - description
+              properties:
+                description:
+                  type: string
+                  description: File description metadata
+                file:
+                  type: string
+                  format: binary
+                  description: File to upload
+      responses:
+        '200':
+          description: Upload successful
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/UploadResponse'
+        '400':
+          description: Bad request
+
+  /upload/optional:
+    post:
+      operationId: uploadOptionalFile
+      summary: Upload an optional file
+      description: Tests async multipart file upload with optional file parameter
+      requestBody:
+        content:
+          multipart/form-data:
+            schema:
+              type: object
+              properties:
+                metadata:
+                  type: string
+                  description: Optional metadata string
+                file:
+                  type: string
+                  format: binary
+                  description: Optional file to upload
+      responses:
+        '200':
+          description: Upload successful
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/UploadResponse'
+
+  /upload/multiple-fields:
+    post:
+      operationId: uploadMultipleFields
+      summary: Upload with multiple form fields
+      description: Tests async multipart with multiple files and text fields
+      requestBody:
+        content:
+          multipart/form-data:
+            schema:
+              type: object
+              required:
+                - primaryFile
+              properties:
+                title:
+                  type: string
+                  description: Upload title
+                tags:
+                  type: array
+                  items:
+                    type: string
+                  description: Tags for the upload
+                primaryFile:
+                  type: string
+                  format: binary
+                  description: Primary file (required)
+                thumbnail:
+                  type: string
+                  format: binary
+                  description: Optional thumbnail file
+      responses:
+        '200':
+          description: Upload successful
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/UploadResponse'
+        '400':
+          description: Bad request
+
+components:
+  schemas:
+    UploadResponse:
+      type: object
+      required:
+        - success
+        - fileCount
+      properties:
+        success:
+          type: boolean
+          description: Whether the upload was successful
+        fileCount:
+          type: integer
+          format: int32
+          description: Number of files uploaded
+        message:
+          type: string
+          description: Optional message about the upload