From 43b8e8f6f26af5dde465441486c7d9b4c7e586c9 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 24 Sep 2020 14:40:56 +1000
Subject: [PATCH] introspection: add type_name_with_namespace

---
 introspection.hpp      | 66 ++++++++++++++++++++++++------------------
 test/introspection.cpp | 34 +++++++++++++++++++++-
 2 files changed, 71 insertions(+), 29 deletions(-)

diff --git a/introspection.hpp b/introspection.hpp
index 58ba4739..99ab70bb 100644
--- a/introspection.hpp
+++ b/introspection.hpp
@@ -27,7 +27,7 @@
 namespace cruft {
     template <typename T>
     constexpr
-    std::string_view type_name (void)
+    std::string_view type_name_with_namespace (void)
     {
         std::string_view pretty_function (__PRETTY_FUNCTION__);
 
@@ -43,49 +43,59 @@ namespace cruft {
 #error "Unsupported compiler"
 #endif
 
-        // Find the location where the type begins. It will also mark the start of
-        // the type's namespace if the type has one.
-        auto const ns_begin = std::search (
+        // Find the location where the type begins.
+        auto const type_begin = std::search (
             pretty_function.begin (),
             pretty_function.end (),
             prefix.begin (),
             prefix.end ()
-        );
+        ) + prefix.size ();
 
         // Find the point the type name ends. Both use ']', but gcc lists
-        // std::string_view too and so requires the delimiting ';' as a suffix.
+        // std::string_view in the function signature too and so requires the
+        // delimiting ';' as a suffix.
         char const suffixes[] = ";]";
         auto const type_end = std::find_first_of (
-            ns_begin,
+            type_begin,
             pretty_function.end (),
             std::begin (suffixes),
-            std::end (suffixes)
+            std::end   (suffixes)
         );
 
-        // Find the start of the first template parameter (or the end of the
-        // string otherwise), and the end of the template parameters for this
-        // type.
-        //
-        // This cursor will be used to limit the scope of the namespace removal
-        // we're about to do.
-        auto const first_template = std::find (ns_begin, type_end, '<');
-        auto const end_first_template = cruft::search::balanced (first_template, type_end, '<', '>');
+        // Find the start of the first template parameter so we can cut it out.
+        // If this isn't present we end up with a pointer to the end of the
+        // type string which is the end of the type anyway.
+        auto const template_start = std::find (type_begin, type_end, '<');
+        auto const template_end   = cruft::search::balanced (template_start, type_end, '<', '>');
 
-        // Find the end of any namespace symbols
-        auto const ns_symbol = std::find (
-            std::make_reverse_iterator (first_template),
-            std::make_reverse_iterator (ns_begin),
-            ':'
+        return std::string_view (
+            type_begin,
+            std::distance (type_begin, template_end)
         );
-
-        // Compute the start of the symbol's type and return a view over this.
-        auto const data = ns_symbol != std::make_reverse_iterator (ns_begin)
-                          ? &*ns_symbol + 1
-                          : ns_begin + prefix.size ();
-        auto const size = std::distance (data, end_first_template);
-        return std::string_view (data, size);
     }
 
+
+    template <typename T>
+    constexpr
+    std::string_view type_name (void)
+    {
+
+        auto const fullname = type_name_with_namespace<T> ();
+
+        constexpr char const namespace_symbol[] = "::";
+        auto const last_namespace_pos = std::search (
+            std::rbegin (fullname),
+            std::rend   (fullname),
+            namespace_symbol + 0,
+            namespace_symbol + 2
+        );
+
+        auto const length = std::distance (std::rbegin (fullname), last_namespace_pos);
+        auto const offset = fullname.size () - length;
+        return std::string_view (fullname.data () + offset, length);
+    }
+
+
     template <> constexpr std::string_view type_name<i08> (void) { return "i08"; }
     template <> constexpr std::string_view type_name<i16> (void) { return "i16"; }
     template <> constexpr std::string_view type_name<i32> (void) { return "i32"; }
diff --git a/test/introspection.cpp b/test/introspection.cpp
index 29a4b8ae..ef3920a6 100644
--- a/test/introspection.cpp
+++ b/test/introspection.cpp
@@ -19,6 +19,9 @@ namespace bar {
     struct qux {
         short c;
     };
+
+    template <typename>
+    struct templated_qux { };
 }
 
 
@@ -55,6 +58,19 @@ namespace cruft
 }
 
 
+//-----------------------------------------------------------------------------
+template <typename A, typename B>
+static
+bool
+equal (A &&a, B &&b)
+{
+    return std::equal (
+        std::begin (a), std::end (a),
+        std::begin (b), std::end (b)
+    );
+}
+
+
 //-----------------------------------------------------------------------------
 int main ()
 {
@@ -92,7 +108,23 @@ int main ()
     tap.expect_eq (cruft::view (cruft::type_name<f64> ()), "f64", "f64 type_name");
 
     tap.expect_eq (cruft::view (cruft::type_name<foo> ()), "foo", "struct type_name");
-    tap.expect_eq (cruft::view (cruft::type_name<bar::qux> ()), "qux", "namespaced struct type_name");
+    tap.expect_eq (cruft::view (cruft::type_name<bar::qux> ()), "qux", "de-namespaced struct type_name");
+
+    tap.expect (
+        equal (
+            cruft::type_name_with_namespace<bar::qux> (),
+            std::string_view ("bar::qux")
+        ),
+        "namespaced struct"
+    );
+
+    tap.expect (
+        equal (
+            cruft::type_name_with_namespace<bar::templated_qux<int>> (),
+            std::string_view ("bar::templated_qux<int>")
+        ),
+        "namespaced templated struct"
+    );
 
     tap.expect_eq (
         cruft::type_name<templated_with_type<int>> (),