feat: default graph output is mermaid at directory level

Author: nikolay-e

src/treemapper/cli.py

@@ -176,9 +176,9 @@ def _warn_diff_only_flags(args: argparse.Namespace) -> None:
 
 @dataclass
 class GraphArgs:
-    format: str = "json"
+    format: str = "mermaid"
     summary: bool = False
-    level: str = "fragment"
+    level: str = "directory"
     edge_types: list[str] | None = None
     mermaid: bool = False
     cycles: bool = False
@@ -264,16 +264,16 @@ def _build_graph_parser() -> argparse.ArgumentParser:
     graph_parser.add_argument(
         "-f",
         "--format",
-        choices=["json", "graphml"],
-        default="json",
-        help="Graph output format (default: json)",
+        choices=["mermaid", "json", "graphml"],
+        default="mermaid",
+        help="Graph output format (default: mermaid)",
     )
     graph_parser.add_argument("--summary", action="store_true", help="Print graph summary statistics")
     graph_parser.add_argument(
         "--level",
         choices=["fragment", "file", "directory"],
-        default="fragment",
-        help="Granularity level for graph operations (default: fragment)",
+        default="directory",
+        help="Granularity level for graph operations (default: directory)",
     )
     graph_parser.add_argument(
         "--edge-types",

src/treemapper/treemapper.py

@@ -187,11 +187,15 @@ def _format_blast_radius(g: GraphArgs, pg: Any) -> str:
     return "\n".join(lines)
 
 
-def _graph_to_string(pg: Any, fmt: str) -> str:
+def _graph_to_string(pg: Any, fmt: str, level: str = "directory") -> str:
+    from .diffctx.graph_analytics import quotient_graph, to_mermaid
     from .diffctx.graph_export import graph_to_graphml_string, graph_to_json_string
 
     if fmt == "graphml":
         return graph_to_graphml_string(pg)
+    if fmt == "mermaid":
+        qg = quotient_graph(pg, level=level)
+        return to_mermaid(qg)
     return graph_to_json_string(pg)
 
 
@@ -230,7 +234,7 @@ def _handle_graph_mode(args: ParsedArgs) -> str:
 
     has_analysis_flag = any([g.summary, g.cycles, g.hotspots is not None, g.metrics, g.impact, g.blast_radius, g.mermaid])
     if not has_analysis_flag:
-        parts.append(_graph_to_string(pg, g.format))
+        parts.append(_graph_to_string(pg, g.format, level=g.level))
 
     return "\n".join(parts) + "\n" if parts else ""
 

tests/test_graph.py

@@ -361,9 +361,14 @@ def test_edge_type_filter(self, tmp_path):
 
 
 class TestGraphCLI:
-    def test_default_json_export(self, graph_git_project):
+    def test_default_mermaid_export(self, graph_git_project):
         result = _run_graph_cli([".", "-q"], cwd=graph_git_project)
         assert result.returncode == 0
+        assert result.stdout.startswith("graph LR")
+
+    def test_json_format(self, graph_git_project):
+        result = _run_graph_cli([".", "-f", "json", "-q"], cwd=graph_git_project)
+        assert result.returncode == 0
         data = json.loads(result.stdout)
         assert data["type"] == "project_graph"
 
@@ -401,7 +406,7 @@ def test_metrics(self, graph_git_project):
 
     def test_output_file(self, graph_git_project):
         out_file = graph_git_project / "graph.json"
-        result = _run_graph_cli([".", "-o", str(out_file), "-q"], cwd=graph_git_project)
+        result = _run_graph_cli([".", "-f", "json", "-o", str(out_file), "-q"], cwd=graph_git_project)
         assert result.returncode == 0
         assert out_file.exists()
         data = json.loads(out_file.read_text())