Fix isRelativeUrl incorrectly detecting URLs containing @, -, ~, . as not relative. (#22768)

Author: Romanow88

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

@@ -235,7 +235,7 @@ private static URL getDefaultUrl() {
     public static boolean isRelativeUrl(List<Server> servers) {
         if (servers != null && servers.size() > 0) {
             final Server firstServer = servers.get(0);
-            return Pattern.matches("^(\\/[\\w\\d]+)+", firstServer.getUrl());
+            return Pattern.matches("^(\\/[\\w\\d.~@-]+)+", firstServer.getUrl());
         }
         return false;
     }

modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultGeneratorTest.java

@@ -671,6 +671,32 @@ public void testHandlesTrailingSlashInServers() {
         Assert.assertEquals(servers.get(2).url, "http://notrailingslash.io:80/v2");
     }
 
+    @Test
+    public void testHandlesRelativeUrlsWithSpecialChars() {
+        final Map<String, String> specToBasePath = Map.of(
+          "src/test/resources/3_0/relative-url-point.yaml", "/api/v4.0",
+          "src/test/resources/3_0/relative-url-dash.yaml", "/api-v3",
+          "src/test/resources/3_0/relative-url-tilde.yaml", "/~api/v5",
+          "src/test/resources/3_0/relative-url-at.yaml", "/api/@6"
+        );
+
+        specToBasePath.forEach((spec, expectedBasePath) -> {
+            OpenAPI openAPI = TestUtils.parseFlattenSpec(spec);
+            ClientOptInput opts = new ClientOptInput();
+            opts.openAPI(openAPI);
+            DefaultCodegen config = new DefaultCodegen();
+            config.setStrictSpecBehavior(false);
+            opts.config(config);
+            final DefaultGenerator generator = new DefaultGenerator();
+            generator.opts(opts);
+            generator.configureGeneratorProperties();
+
+            Map<String, Object> bundle = generator.buildSupportFileBundle(new ArrayList<>(), new ArrayList<>(), new ArrayList<>());
+            final String actualBasePath = (String) bundle.get("basePath");
+            Assert.assertEquals(actualBasePath, expectedBasePath);
+        });
+    }
+
     @Test
     public void testHandlesRelativeUrlsInServers() {
         OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/issue_10056.yaml");

modules/openapi-generator/src/test/resources/3_0/relative-url-at.yaml

@@ -0,0 +1,15 @@
+openapi: 3.0.1
+info:
+  title: OpenAPI Petstore
+  description: "sample spec"
+  license:
+    name: Apache-2.0
+    url: https://www.apache.org/licenses/LICENSE-2.0.html
+  version: 1.0.0
+servers:
+  - url: /api/@6
+tags: []
+paths: {}
+components:
+  schemas: {}
+  securitySchemes: {}

modules/openapi-generator/src/test/resources/3_0/relative-url-dash.yaml

@@ -0,0 +1,15 @@
+openapi: 3.0.1
+info:
+  title: OpenAPI Petstore
+  description: "sample spec"
+  license:
+    name: Apache-2.0
+    url: https://www.apache.org/licenses/LICENSE-2.0.html
+  version: 1.0.0
+servers:
+  - url: /api-v3
+tags: []
+paths: {}
+components:
+  schemas: {}
+  securitySchemes: {}

modules/openapi-generator/src/test/resources/3_0/relative-url-point.yaml

@@ -0,0 +1,15 @@
+openapi: 3.0.1
+info:
+  title: OpenAPI Petstore
+  description: "sample spec"
+  license:
+    name: Apache-2.0
+    url: https://www.apache.org/licenses/LICENSE-2.0.html
+  version: 1.0.0
+servers:
+  - url: /api/v4.0
+tags: []
+paths: {}
+components:
+  schemas: {}
+  securitySchemes: {}

modules/openapi-generator/src/test/resources/3_0/relative-url-tilde.yaml

@@ -0,0 +1,15 @@
+openapi: 3.0.1
+info:
+  title: OpenAPI Petstore
+  description: "sample spec"
+  license:
+    name: Apache-2.0
+    url: https://www.apache.org/licenses/LICENSE-2.0.html
+  version: 1.0.0
+servers:
+  - url: /~api/v5
+tags: []
+paths: {}
+components:
+  schemas: {}
+  securitySchemes: {}