feat: tagfiles generation for cross-referencing in doxygen format

include/mrdocs/Corpus.hpp

@@ -160,6 +160,39 @@ class MRDOCS_VISIBLE
         }
     }
 
+    /** Visit the members of specified Info.
+
+        This function iterates the members of the specified
+        Info `I`. For each member associated with a
+        function with the same name as the member, the
+        function object `f` is invoked with the member
+        as the first argument, followed by `args...`.
+
+        When there are more than one member function
+        with the same name, the function object `f` is
+        invoked with an @ref OverloadSet as the first
+        argument, followed by `args...`.    
+
+        @param I The Info to traverse.
+        @param pred The predicate to use to determine if the member should be visited.
+        @param f The function to invoke with the member as the first argument, followed by `args...`.
+        @param args The arguments to pass to the function.
+    */
+    template <InfoParent T, class Pred, class F, class... Args>
+    void
+    traverseIf(
+        T const& I, Pred&& pred, F&& f, Args&&... args) const
+    {
+        for (auto const& id : I.Members)
+        {
+            if (pred(get(id))) 
+            {
+                visit(get(id), std::forward<F>(f),
+                      std::forward<Args>(args)...);
+            }
+        }
+    }
+
     /** Visit the function members of specified Info.
 
         This function iterates the members of the specified

include/mrdocs/Generator.hpp

@@ -64,6 +64,7 @@ class MRDOCS_VISIBLE
         @li "adoc" Asciidoctor
         @li "xml" XML
         @li "html" HTML
+        @li "tagfile" Tagfile
 
         The returned string should not include
         a leading period.

src/lib/Gen/tagfile/TagfileGenerator.cpp

@@ -0,0 +1,45 @@
+//
+// This is a derivative work. originally part of the LLVM Project.
+// Licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// Copyright (c) 2024 Fernando Pelliccioni ([email protected])
+//
+// Official repository: https://github.com/cppalliance/mrdocs
+//
+
+#include "TagfileGenerator.hpp"
+#include "TagfileWriter.hpp"
+#include "lib/Support/Radix.hpp"
+#include "lib/Support/RawOstream.hpp"
+#include <mrdocs/Support/Error.hpp>
+#include <mrdocs/Metadata.hpp>
+
+namespace clang {
+namespace mrdocs {
+namespace tagfile {
+
+Error
+TagfileGenerator::
+buildOne(
+    std::ostream& os,
+    Corpus const& corpus) const
+{
+    namespace fs = llvm::sys::fs;
+    RawOstream raw_os(os);
+    return TagfileWriter(raw_os, corpus).build();
+}
+
+} // tagfile
+
+//------------------------------------------------
+
+std::unique_ptr<Generator>
+makeTagfileGenerator()
+{
+    return std::make_unique<tagfile::TagfileGenerator>();
+}
+
+} // mrdocs
+} // clang

src/lib/Gen/tagfile/TagfileGenerator.hpp

@@ -0,0 +1,57 @@
+//
+// This is a derivative work. originally part of the LLVM Project.
+// Licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// Copyright (c) 2024 Fernando Pelliccioni ([email protected])
+//
+// Official repository: https://github.com/cppalliance/mrdocs
+//
+
+#ifndef MRDOCS_LIB_GEN_TAGFILE_TAGFILEGENERATOR_HPP
+#define MRDOCS_LIB_GEN_TAGFILE_TAGFILEGENERATOR_HPP
+
+#include <mrdocs/Platform.hpp>
+#include <mrdocs/Generator.hpp>
+#include <mrdocs/MetadataFwd.hpp>
+#include <mrdocs/Metadata/Javadoc.hpp>
+#include <optional>
+
+namespace clang {
+namespace mrdocs {
+namespace tagfile {
+
+//------------------------------------------------
+
+struct TagfileGenerator : Generator
+{
+    std::string_view
+    id() const noexcept override
+    {
+        return "tagfile";
+    }
+
+    std::string_view
+    displayName() const noexcept override
+    {
+        return "Doxygen Tagfile";
+    }
+
+    std::string_view
+    fileExtension() const noexcept override
+    {
+        return "tag.xml";
+    }
+
+    Error
+    buildOne(
+        std::ostream& os,
+        Corpus const& corpus) const override;
+};
+
+} // tagfile
+} // mrdocs
+} // clang
+
+#endif