[Rust] Configurable default features from reqwest dependency (#22041)

* fix(rust): Remove default features from reqwest dependency

This change removes the default features (specifically native-tls) from the reqwest
dependency in the Rust client generator. This allows users to explicitly choose
their TLS backend without automatically including openssl-sys as a transitive dependency.

Users can now explicitly enable TLS backends using feature flags:
- native-tls
- rustls-tls
- default-tls

Fixes #21933

* feat(rust): Add reqwestDefaultFeatures option with backward-compatible default

This change adds a new generator option `reqwestDefaultFeatures` that allows
users to configure the default Cargo features for the reqwest dependency.

The option accepts:
- An array of strings in YAML config: reqwestDefaultFeatures: ["native-tls"]
- A comma-separated string via CLI: --additional-properties=reqwestDefaultFeatures=native-tls
- An empty value for no defaults: reqwestDefaultFeatures: []

Default value: ["native-tls"] (maintains backward compatibility)

This addresses the feedback in #21933 to make the change opt-in rather than
breaking existing users.

Users can now:
- Keep the current behavior (default)
- Opt-out: reqwestDefaultFeatures: []
- Use alternative TLS: reqwestDefaultFeatures: ["rustls-tls"]
- Combine features: reqwestDefaultFeatures: ["native-tls", "cookies"]

Fixes #21933

docs/generators/rust.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |packageName|Rust package name (convention: lowercase).| |openapi|
 |packageVersion|Rust package version.| |1.0.0|
 |preferUnsignedInt|Prefer unsigned integers where minimum value is >= 0| |false|
+|reqwestDefaultFeatures|Default features for the reqwest dependency (comma-separated). Use empty for no defaults. This option is for 'reqwest' and 'reqwest-trait' library only.| |native-tls|
 |supportAsync|If set, generate async function call instead. This option is for 'reqwest' library only| |true|
 |supportMiddleware|If set, add support for reqwest-middleware. This option is for 'reqwest' and 'reqwest-trait' library only| |false|
 |supportMultipleResponses|If set, return type wraps an enum of all possible 2xx schemas. This option is for 'reqwest' and 'reqwest-trait' library only| |false|

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

@@ -58,6 +58,7 @@ public class RustClientCodegen extends AbstractRustCodegen implements CodegenCon
     @Setter private boolean preferUnsignedInt = false;
     @Setter private boolean bestFitInt = false;
     @Setter private boolean avoidBoxedModels = false;
+    private List<String> reqwestDefaultFeatures = Arrays.asList("native-tls");
 
     public static final String PACKAGE_NAME = "packageName";
     public static final String EXTERN_CRATE_NAME = "externCrateName";
@@ -77,6 +78,7 @@ public class RustClientCodegen extends AbstractRustCodegen implements CodegenCon
     public static final String TOP_LEVEL_API_CLIENT = "topLevelApiClient";
     public static final String MOCKALL = "mockall";
     public static final String BON_BUILDER = "useBonBuilder";
+    public static final String REQWEST_DEFAULT_FEATURES = "reqwestDefaultFeatures";
 
     @Setter protected String packageName = "openapi";
     @Setter protected String packageVersion = "1.0.0";
@@ -227,6 +229,8 @@ public class RustClientCodegen extends AbstractRustCodegen implements CodegenCon
                 .defaultValue(Boolean.FALSE.toString()));
         cliOptions.add(new CliOption(BON_BUILDER, "Use the bon crate for building parameter types. This option is for the 'reqwest-trait' library only", SchemaTypeUtil.BOOLEAN_TYPE)
                 .defaultValue(Boolean.FALSE.toString()));
+        cliOptions.add(new CliOption(REQWEST_DEFAULT_FEATURES, "Default features for the reqwest dependency (comma-separated). Use empty for no defaults. This option is for 'reqwest' and 'reqwest-trait' library only.")
+                .defaultValue("native-tls"));
 
         supportedLibraries.put(HYPER_LIBRARY, "HTTP client: Hyper (v1.x).");
         supportedLibraries.put(HYPER0X_LIBRARY, "HTTP client: Hyper (v0.x).");
@@ -431,6 +435,21 @@ public class RustClientCodegen extends AbstractRustCodegen implements CodegenCon
         }
         writePropertyBack(AVOID_BOXED_MODELS, getAvoidBoxedModels());
 
+        if (additionalProperties.containsKey(REQWEST_DEFAULT_FEATURES)) {
+            Object value = additionalProperties.get(REQWEST_DEFAULT_FEATURES);
+            if (value instanceof List) {
+                reqwestDefaultFeatures = (List<String>) value;
+            } else if (value instanceof String) {
+                String str = (String) value;
+                if (str.isEmpty()) {
+                    reqwestDefaultFeatures = new ArrayList<>();
+                } else {
+                    reqwestDefaultFeatures = Arrays.asList(str.split(",\\s*"));
+                }
+            }
+        }
+        additionalProperties.put(REQWEST_DEFAULT_FEATURES, reqwestDefaultFeatures);
+
         additionalProperties.put(CodegenConstants.PACKAGE_NAME, packageName);
         additionalProperties.put(CodegenConstants.PACKAGE_VERSION, packageVersion);
         additionalProperties.put(EXTERN_CRATE_NAME, getExternCrateName());

modules/openapi-generator/src/main/resources/rust/Cargo.mustache

@@ -88,7 +88,7 @@ google-cloud-token = "^0.1"
 {{/supportAsync}}
 
 [features]
-default = ["native-tls"]
+default = [{{#reqwestDefaultFeatures}}"{{.}}"{{^-last}}, {{/-last}}{{/reqwestDefaultFeatures}}]
 native-tls = ["reqwest/native-tls"]
 rustls-tls = ["reqwest/rustls-tls"]
 {{/reqwest}}
@@ -109,7 +109,7 @@ mockall = { version = "^0.13", optional = true}
 bon = { version = "2.3", optional = true }
 {{/useBonBuilder}}
 [features]
-default = ["native-tls"]
+default = [{{#reqwestDefaultFeatures}}"{{.}}"{{^-last}}, {{/-last}}{{/reqwestDefaultFeatures}}]
 native-tls = ["reqwest/native-tls"]
 rustls-tls = ["reqwest/rustls-tls"]
 {{#mockall}}