[plantuml] enable default template

Author: hoe-jo

plantuml/parser/integration_test/class_diagram/empty_template_args/empty_template_args.puml

@@ -0,0 +1,20 @@
+' *******************************************************************************
+' Copyright (c) 2026 Contributors to the Eclipse Foundation
+'
+' See the NOTICE file(s) distributed with this work for additional
+' information regarding copyright ownership.
+'
+' This program and the accompanying materials are made available under the
+' terms of the Apache License Version 2.0 which is available at
+' https://www.apache.org/licenses/LICENSE-2.0
+'
+' SPDX-License-Identifier: Apache-2.0
+' *******************************************************************************
+@startuml empty_template_args
+
+class Skeleton {
+    + OnFinished(const safecpp::Scope<>& scope, std::less<> comparator): Result<void>
+    + scope : safecpp::Scope<>
+}
+
+@enduml

plantuml/parser/integration_test/class_diagram/empty_template_args/output.json

@@ -0,0 +1,60 @@
+{
+    "empty_template_args.puml": {
+        "name": "empty_template_args",
+        "entities": [
+            {
+                "id": "Skeleton",
+                "name": "Skeleton",
+                "enclosing_namespace_id": null,
+                "entity_type": "Class",
+                "type_aliases": [],
+                "methods": [
+                    {
+                        "name": "OnFinished",
+                        "return_type": "Result<void>",
+                        "visibility": "public",
+                        "parameters": [
+                            {
+                                "name": "scope",
+                                "param_type": "const safecpp::Scope<>&",
+                                "is_variadic": false,
+                                "is_pack_expansion": false
+                            },
+                            {
+                                "name": "comparator",
+                                "param_type": "std::less<>",
+                                "is_variadic": false,
+                                "is_pack_expansion": false
+                            }
+                        ],
+                        "template_parameters": null,
+                        "modifiers": [],
+                        "source_location": {
+                            "file": "",
+                            "line": 16
+                        }
+                    }
+                ],
+                "template_parameters": null,
+                "enum_literals": [],
+                "variables": [
+                    {
+                        "name": "scope",
+                        "data_type": "safecpp::Scope<>",
+                        "visibility": "public",
+                        "is_static": false,
+                        "source_location": {
+                            "file": "",
+                            "line": 17
+                        }
+                    }
+                ],
+                "relationships": [],
+                "source_location": {
+                    "file": "plantuml/parser/integration_test/class_diagram/empty_template_args/empty_template_args.puml",
+                    "line": 15
+                }
+            }
+        ]
+    }
+}

plantuml/parser/puml_parser/src/class_diagram/src/class_parser.rs

@@ -1335,6 +1335,71 @@ mod tests {
         assert_eq!(class_def.attributes[0].source_location.line, 3);
     }
 
+    fn parse_single_class_member_file(member: &str) -> Result<ClassUmlFile, ClassError> {
+        let input = format!("@startuml\nclass A {{\n    {member}\n}}\n@enduml\n");
+        let mut parser = PumlClassParser;
+        parser.parse_file(
+            &std::rc::Rc::new(std::path::PathBuf::from("test.puml")),
+            &input,
+            LogLevel::Info,
+        )
+    }
+
+    #[test]
+    fn test_parse_empty_template_args_in_types() {
+        let result = parse_single_class_member_file(
+            "+Run(const safecpp::Scope<>& scope, std::vector<Foo<>> items): Bar<>",
+        )
+        .unwrap();
+
+        let ClassUmlTopLevel::Types(Element::ClassDef(class_def)) = &result.elements[0] else {
+            panic!("expected class element");
+        };
+
+        let method = &class_def.methods[0];
+        assert_eq!(
+            method.params[0].param_type.as_deref(),
+            Some("const safecpp::Scope<>&")
+        );
+        assert_eq!(
+            method.params[1].param_type.as_deref(),
+            Some("std::vector<Foo<>>")
+        );
+        assert_eq!(method.r#type.as_deref(), Some("Bar<>"));
+    }
+
+    #[test]
+    fn test_parse_empty_template_args_in_attribute() {
+        let result = parse_single_class_member_file("+scope : safecpp::Scope<>").unwrap();
+
+        let ClassUmlTopLevel::Types(Element::ClassDef(class_def)) = &result.elements[0] else {
+            panic!("expected class element");
+        };
+
+        assert_eq!(
+            class_def.attributes[0].r#type.as_deref(),
+            Some("safecpp::Scope<>")
+        );
+    }
+
+    #[test]
+    fn test_parse_const_qualifier_after_empty_template_args() {
+        let result = parse_single_class_member_file("+Get(): Foo<> <<const>>").unwrap();
+
+        let ClassUmlTopLevel::Types(Element::ClassDef(class_def)) = &result.elements[0] else {
+            panic!("expected class element");
+        };
+
+        assert_eq!(class_def.methods[0].r#type.as_deref(), Some("Foo<>"));
+        assert_eq!(class_def.methods[0].modifiers, vec!["<<const>>"]);
+    }
+
+    #[test]
+    fn test_parse_malformed_template_args_rejected() {
+        assert!(parse_single_class_member_file("+f(Foo<int, > a)").is_err());
+        assert!(parse_single_class_member_file("+f(Foo<<int>> a)").is_err());
+    }
+
     #[test]
     fn test_parse_type_alias_source_location() {
         let input = r#"@startuml

plantuml/parser/puml_parser/src/class_diagram/test/integration_test.rs

@@ -220,6 +220,11 @@ fn test_param_templete() {
     run_class_diagram_parser_case("param_templete");
 }
 
+#[test]
+fn test_empty_template_args() {
+    run_class_diagram_parser_case("empty_template_args");
+}
+
 #[test]
 fn test_relationship_arrows() {
     run_class_diagram_parser_case("relationship_arrows");

plantuml/parser/puml_parser/src/grammar/class.pest

@@ -30,7 +30,7 @@ type_expr = { brace_enclosed_type | const_prefix* ~ prefix_array_prefix* ~ quali
 
 qualified_type = @{ ("::")? ~ identifier ~ (("::" | (!".." ~ ".")) ~ identifier)* }
 
-generic_type_args = { "<" ~ !"<" ~ type_arg ~ ("," ~ type_arg)* ~ ">" }
+generic_type_args = { "<" ~ !"<" ~ (type_arg ~ ("," ~ type_arg)*)? ~ ">" }
 
 type_arg = { type_expr | NUMBER }
 type_expr_list = { type_expr ~ ("," ~ type_expr)* }

plantuml/parser/puml_parser/tests/class_diagram/empty_template_args/empty_template_args.puml

@@ -0,0 +1,24 @@
+' *******************************************************************************
+' Copyright (c) 2026 Contributors to the Eclipse Foundation
+'
+' See the NOTICE file(s) distributed with this work for additional
+' information regarding copyright ownership.
+'
+' This program and the accompanying materials are made available under the
+' terms of the Apache License Version 2.0 which is available at
+' https://www.apache.org/licenses/LICENSE-2.0
+'
+' SPDX-License-Identifier: Apache-2.0
+' *******************************************************************************
+@startuml empty_template_args
+
+class "lola::SkeletonMethod" as lola_SkeletonMethod {
+    +OnProxyMethodSubscribeFinished(std::optional<span<std::byte>>, const safecpp::Scope<>&, uid_t uid): Result<void>
+    +Compare(std::less<> comparator)
+    +GetScope(): safecpp::Scope<>
+    +Wrap(std::vector<Foo<>> items, Bar<Baz<>, int>* ptr)
+    +Stop() <<const>>
+    +scope : safecpp::Scope<>
+}
+
+@enduml

plantuml/parser/puml_parser/tests/class_diagram/empty_template_args/output.json

@@ -0,0 +1,132 @@
+{
+  "empty_template_args.puml": {
+    "name": "empty_template_args",
+    "elements": [
+      {
+        "Types": {
+          "ClassDef": {
+            "name": {
+              "internal": "lola::SkeletonMethod",
+              "display": "lola_SkeletonMethod"
+            },
+            "namespace": "",
+            "package": "",
+            "source_location": {
+              "file": "",
+              "line": 15
+            },
+            "is_abstract": false,
+            "type_aliases": [],
+            "attributes": [
+              {
+                "visibility": "Public",
+                "name": "scope",
+                "type": "safecpp::Scope<>",
+                "modifiers": [],
+                "source_location": {
+                  "file": "",
+                  "line": 21
+                }
+              }
+            ],
+            "methods": [
+              {
+                "visibility": "Public",
+                "name": "OnProxyMethodSubscribeFinished",
+                "template_parameters": null,
+                "params": [
+                  {
+                    "name": null,
+                    "param_type": "std::optional<span<std::byte>>"
+                  },
+                  {
+                    "name": null,
+                    "param_type": "const safecpp::Scope<>&"
+                  },
+                  {
+                    "name": "uid",
+                    "param_type": "uid_t"
+                  }
+                ],
+                "type": "Result<void>",
+                "modifiers": [],
+                "source_location": {
+                  "file": "",
+                  "line": 16
+                }
+              },
+              {
+                "visibility": "Public",
+                "name": "Compare",
+                "template_parameters": null,
+                "params": [
+                  {
+                    "name": "comparator",
+                    "param_type": "std::less<>"
+                  }
+                ],
+                "type": null,
+                "modifiers": [],
+                "source_location": {
+                  "file": "",
+                  "line": 17
+                }
+              },
+              {
+                "visibility": "Public",
+                "name": "GetScope",
+                "template_parameters": null,
+                "params": [],
+                "type": "safecpp::Scope<>",
+                "modifiers": [],
+                "source_location": {
+                  "file": "",
+                  "line": 18
+                }
+              },
+              {
+                "visibility": "Public",
+                "name": "Wrap",
+                "template_parameters": null,
+                "params": [
+                  {
+                    "name": "items",
+                    "param_type": "std::vector<Foo<>>"
+                  },
+                  {
+                    "name": "ptr",
+                    "param_type": "Bar<Baz<>, int>*"
+                  }
+                ],
+                "type": null,
+                "modifiers": [],
+                "source_location": {
+                  "file": "",
+                  "line": 19
+                }
+              },
+              {
+                "visibility": "Public",
+                "name": "Stop",
+                "template_parameters": null,
+                "params": [],
+                "type": null,
+                "modifiers": [
+                  "<<const>>"
+                ],
+                "source_location": {
+                  "file": "",
+                  "line": 20
+                }
+              }
+            ],
+            "template_parameters": null,
+            "extends": [],
+            "implements": []
+          }
+        }
+      }
+    ],
+    "relationships": []
+  }
+}

plantuml/parser/puml_resolver/src/class_diagram/test/class_resolver_test.rs

@@ -126,3 +126,8 @@ fn test_c_variadic_method() {
 fn test_class_template_pack() {
     run_class_resolver_case("class_template_pack");
 }
+
+#[test]
+fn test_empty_template_args() {
+    run_class_resolver_case("empty_template_args");
+}