test: adding missing round-trip test for graphviz format

test/Jamfile.v2

@@ -79,8 +79,8 @@ alias graph_test_regular :
     [ run graph.cpp : : : <define>TEST=8 : graph_8 ]
     [ run graph.cpp : : : <define>TEST=9 : graph_9 ]
     [ compile graph_concepts.cpp ]
-    [ run graphviz_test.cpp
-            /boost/graph//boost_graph : --log_level=all ]
+    [ run graphviz_test.cpp /boost/graph//boost_graph : --log_level=all ]
+    [ run graphviz_round_trip_test.cpp /boost/graph//boost_graph ]
     [ run metis_test.cpp : $(METIS_INPUT_FILE) ]
     [ run gursoy_atun_layout_test.cpp  : : : [ requires cxx11_noexcept cxx11_rvalue_references sfinae_expr cxx11_auto_declarations cxx11_lambdas cxx11_unified_initialization_syntax cxx11_hdr_tuple cxx11_hdr_initializer_list cxx11_hdr_chrono cxx11_thread_local cxx11_constexpr cxx11_nullptr cxx11_numeric_limits cxx11_decltype cxx11_hdr_array cxx11_hdr_atomic cxx11_hdr_type_traits cxx11_allocator cxx11_explicit_conversion_operators ] ]
     [ run layout_test.cpp : : : <test-info>always_show_run_output <toolset>intel:<debug-symbols>off [ requires cxx11_noexcept cxx11_rvalue_references sfinae_expr cxx11_auto_declarations cxx11_lambdas cxx11_unified_initialization_syntax cxx11_hdr_tuple cxx11_hdr_initializer_list cxx11_hdr_chrono cxx11_thread_local cxx11_constexpr cxx11_nullptr cxx11_numeric_limits cxx11_decltype cxx11_hdr_array cxx11_hdr_atomic cxx11_hdr_type_traits cxx11_allocator cxx11_explicit_conversion_operators ] ]

test/graphviz_round_trip_test.cpp

@@ -0,0 +1,122 @@
+// Copyright (C) 2026 Arnaud Becheler
+//
+// Use, modification and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+// Round-trips a graph through write_graphviz_dp and read_graphviz. The vertex
+// and edge string values are chosen to straddle the DOT quoting boundary in
+// escape_dot_string, so a writer that mis-quotes produces DOT that re-reads
+// into different values and fails the comparison.
+
+#include <boost/graph/adjacency_list.hpp>
+#include <boost/graph/graphviz.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace
+{
+
+struct vertex_props
+{
+    std::string node_id;
+    std::string label;
+};
+
+struct edge_props
+{
+    std::string elabel;
+};
+
+using graph_t = boost::adjacency_list< boost::vecS, boost::vecS,
+    boost::directedS, vertex_props, edge_props >;
+
+// First four are valid unquoted DOT ids/numerals
+// the rest force quoting or escaping (space, embedded quote, digit-led identifier, multi-dot numeral).
+const std::vector< std::string >& boundary_labels()
+{
+    static const std::vector< std::string > labels = { "plain", "id_123", "42",
+        "-3.14", "has space", "has\"quote", "9lives", "1.2.3" };
+    return labels;
+}
+
+graph_t make_graph()
+{
+    const std::vector< std::string >& labels = boundary_labels();
+    graph_t g;
+    std::vector< graph_t::vertex_descriptor > added;
+    added.reserve(labels.size());
+    for (std::size_t i = 0; i < labels.size(); ++i)
+    {
+        graph_t::vertex_descriptor vd = boost::add_vertex(g);
+        g[vd].node_id = "n" + std::to_string(i);
+        g[vd].label = labels[i];
+        added.push_back(vd);
+    }
+    for (std::size_t i = 1; i < added.size(); ++i)
+    {
+        graph_t::edge_descriptor ed
+            = boost::add_edge(added[i - 1], added[i], g).first;
+        g[ed].elabel = "e " + std::to_string(i); // space forces quoting
+    }
+    return g;
+}
+
+std::map< std::string, std::string > labels_by_id(const graph_t& g)
+{
+    std::map< std::string, std::string > m;
+    graph_t::vertex_iterator it, end;
+    for (boost::tie(it, end) = boost::vertices(g); it != end; ++it)
+        m[g[*it].node_id] = g[*it].label;
+    return m;
+}
+
+std::multiset< std::string > edges_repr(const graph_t& g)
+{
+    std::multiset< std::string > s;
+    graph_t::edge_iterator it, end;
+    for (boost::tie(it, end) = boost::edges(g); it != end; ++it)
+    {
+        const std::string src = g[boost::source(*it, g)].node_id;
+        const std::string tgt = g[boost::target(*it, g)].node_id;
+        s.insert(src + "->" + tgt + ":" + g[*it].elabel);
+    }
+    return s;
+}
+
+boost::dynamic_properties make_properties(graph_t& g)
+{
+    boost::dynamic_properties dp;
+    dp.property("node_id", boost::get(&vertex_props::node_id, g));
+    dp.property("label", boost::get(&vertex_props::label, g));
+    dp.property("elabel", boost::get(&edge_props::elabel, g));
+    return dp;
+}
+
+} // namespace
+
+int main()
+{
+    graph_t g = make_graph();
+    boost::dynamic_properties dp = make_properties(g);
+
+    std::ostringstream out;
+    boost::write_graphviz_dp(out, g, dp, std::string("node_id"));
+    const std::string text = out.str();
+
+    graph_t g2;
+    boost::dynamic_properties dp2 = make_properties(g2);
+    const bool ok = boost::read_graphviz(text.begin(), text.end(), g2, dp2, "node_id");
+    BOOST_TEST(ok);
+
+    BOOST_TEST(boost::num_vertices(g) == boost::num_vertices(g2));
+    BOOST_TEST(boost::num_edges(g) == boost::num_edges(g2));
+    BOOST_TEST(labels_by_id(g) == labels_by_id(g2));
+    BOOST_TEST(edges_repr(g) == edges_repr(g2));
+
+    return boost::report_errors();
+}