Improve documentation

Author: jpfinne

docs/customization.md

@@ -647,7 +647,7 @@ java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generat
 
 The `FILTER` parameter allows selective inclusion of API operations based on specific criteria. It applies the `x-internal: true` property to operations that do **not** match the specified values, preventing them from being generated. Multiple filters can be separated by a semicolon.
 
-### Available Filters
+### Available FILTER filters
 
 - **`operationId`**  
   When set to `operationId:addPet|getPetById`, operations **not** matching `addPet` or `getPetById` will be marked as internal (`x-internal: true`), and excluded from generation. Matching operations will have `x-internal: false`.
@@ -715,3 +715,34 @@ Into this securityScheme:
       scheme: bearer
       type: http
 ```
+
+- `REMOVE_FILTER`
+
+The `REMOVE_FILTER` parameter allows the removal of elements in an openAPI document. A semicolon can separate multiple filters.
+
+### Available REMOVE_FILTER filters
+
+- **`internal`**  
+  When specified as `internal` or set to `internal:true`, all operations, schemas, properties and parameters marked with x-internal: true are removed from the document. Optionally set individual options like in `internal:operations|schemas|properties|parameters`
+
+- **`deprecated`**  
+  When specified as `deprecated` or set to `deprecated:true`, all operations, schemas, properties and parameters marked with deprecated: true are removed.
+
+- **`tags`**   
+  When specified as `tags` or set to `tags:true`, all tags are removed.
+  When set to `tags:store|user` all tags whose name is store or user are removed.
+  When set to `tags:keepOnlyFirstTag` perform the KEEP_ONLY_FIRST_TAG_IN_OPERATION normalization
+
+- **`vendorExtensions`**  
+  When specified as `vendorExtensions` or set to `vendorExtensions:true`, remove all vendorExtensions (including x-internal).
+  When set to `vendorExtensions:x-role|x-groups`, remove all `x-role` and `x-groups` vendorExtensions. When set to `vendorExtensions:x-internal`, perform the equivalent of REMOVE_X_INTERNAL normalization.
+
+- **`unused`**  
+  When specified as `unused` or set to `unused:true`, remove all unused schemas, tags, requestBodies, responses and parameters.
+  Optionally set individual options like in `unused:schemas|tags|requestBodies|responses|parameters`
+
+Example:
+```
+java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g openapi -i modules/openapi-generator/src/test/resources/3_1/java/petstore.yaml -o /tmp/openapi/ --openapi-normalizer FILTER=tag:pet --openapi-normalizer REMOVE_FILTER=internal;unused
+```
+generates an openapi.json without the store and user operations.

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

@@ -2255,8 +2255,6 @@ public boolean parse() {
             } catch (RuntimeException e) {
                 String message = String.format(Locale.ROOT, "FILTER rule [%s] `. Error: %s",
                         filters, e.getMessage());
-                // throw an exception. This is a breaking change compared to pre 7.16.0
-                // Workaround: fix the syntax!
                 throw new IllegalArgumentException(message);
             }
         }
@@ -2266,11 +2264,6 @@ public boolean hasFilter() {
         }
 
         private void doParse() {
-            if ("true".equals(filters)) {
-                allTrue();
-                return;
-            }
-
             for (String filter : filters.split(";")) {
                 filter = filter.trim();
                 String[] filterStrs = filter.split(":");
@@ -2346,20 +2339,6 @@ protected void parseFails(String filterName, String filterValue) {
             throw new IllegalArgumentException("filter not supported :[" + filterName + ":" + filterValue + "]");
         }
 
-        private void allTrue() {
-            hasFilter = true;
-
-            internalOperations = true;
-            internalSchemas = true;
-            internalProperties = true;
-            internalParameters = true;
-
-            unusedSchemas = true;
-            unusedParameters = true;
-            unusedTags = true;
-            unusedRequestBodies = true;
-        }
-
         protected boolean matchTag(Operation operation, int index, String tag) {
             if (removeAllTags) {
                 return true;

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

@@ -1283,6 +1283,10 @@ public Object[][] getTestConfigs() {
         URL path = getClass().getClassLoader().getResource("openapi_normalizer");
         File[] files = new File(path.getFile())
                 .listFiles(file -> file.getName().endsWith("_config.yaml"));
+
+        if (files == null || files.length == 0) {
+            throw new AssertionError("No test configs found in openapi_normalizer directory.");
+        }
         return Arrays.stream(files)
                 .map(file -> new Object[]{"src/test/resources/openapi_normalizer/" +file.getName()})
                 .toArray(Object[][]::new);