Temporary utility to view a model

.vscode/tasks.json

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+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "label": "Tests: Run pytest",
+      "type": "shell",
+      "command": "${command:python.interpreterPath}",
+      "args": [
+        "-m",
+        "pytest"
+      ],
+      "options": {
+        "cwd": "${workspaceFolder}",
+        "env": {
+          "PYTHONPATH": "${workspaceFolder}/src"
+        }
+      },
+      "group": {
+        "kind": "test",
+        "isDefault": true
+      },
+      "presentation": {
+        "clear": true,
+        "reveal": "always",
+        "panel": "dedicated"
+      },
+      "problemMatcher": []
+    }
+  ]
+}

src/bedit_util/__init__.py

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+"""Small command-line utilities for bedit models."""
+
+from .graphviz import document_to_dot, render_document
+
+__all__ = ["document_to_dot", "render_document"]

src/bedit_util/__main__.py

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+"""Run the Graphviz utility with ``python -m bedit_util``."""
+
+from .graphviz import main
+
+raise SystemExit(main())

src/bedit_util/graphviz.py

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+"""Create Graphviz representations of bedit bond-graph models."""
+
+from __future__ import annotations
+
+import argparse
+import json
+import subprocess
+from pathlib import Path
+
+from bedit_core.bondgraph import BondGraphNetwork, flatten_bondgraph
+from bedit_core.models import (
+    BondCausality,
+    Component,
+    ComponentID,
+    Document,
+    GraphImplementation,
+)
+from bedit_core.serialization import load
+
+
+def document_to_dot(document: Document, component_path: str) -> str:
+    """Return DOT for the hierarchy starting at ``component_path``."""
+    lines = [
+        "digraph bedit {",
+        "  graph [rankdir=LR, bgcolor=\"white\"];",
+        "  node [shape=box, style=\"rounded\", fontname=\"sans-serif\"];",
+        "  edge [fontname=\"sans-serif\", arrowsize=0.8];",
+    ]
+
+    root_id, component, path = _find_component(document, component_path)
+    network = flatten_bondgraph(component)
+    paths = _component_paths(component, path[:-1])
+    node_ids = {
+        id(item): f"{root_id}:{'/'.join(item_path)}"
+        for item, item_path in paths
+    }
+    lines.extend(_nodes(network, node_ids, paths))
+    lines.extend(_bonds(network, node_ids))
+
+    lines.append("}")
+    return "\n".join(lines) + "\n"
+
+
+def render_document(
+    document: Document,
+    component_path: str,
+    output: str | Path,
+    dot_executable: str = "dot",
+) -> Path:
+    """Render one component hierarchy to PNG using Graphviz ``dot``."""
+    output_path = Path(output)
+    try:
+        subprocess.run(
+            [dot_executable, "-Tpng", "-o", str(output_path)],
+            input=document_to_dot(document, component_path),
+            text=True,
+            check=True,
+        )
+    except FileNotFoundError:
+        raise RuntimeError(
+            f"Graphviz executable {dot_executable!r} was not found"
+        ) from None
+    except subprocess.CalledProcessError as exc:
+        raise RuntimeError(f"Graphviz failed with exit code {exc.returncode}") from exc
+    return output_path
+
+
+def main(argv: list[str] | None = None) -> int:
+    """Load a bedit model and render its bond graph as a PNG."""
+    parser = argparse.ArgumentParser(
+        prog="bedit-graphviz",
+        description="Render a .json or .beb bedit model as a Graphviz PNG.",
+    )
+    parser.add_argument("model", type=Path, help="input .json or .beb model")
+    parser.add_argument(
+        "component_path",
+        help="dotted component path, for example Root.Subsystem.Component",
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        type=Path,
+        help="output PNG path (default: input name with .png suffix)",
+    )
+    args = parser.parse_args(argv)
+
+    output = args.output or args.model.with_suffix(".png")
+    render_document(load(args.model), args.component_path, output)
+    print(output)
+    return 0
+
+
+def _component_paths(
+    root: Component,
+    prefix: tuple[str, ...] = (),
+) -> list[tuple[Component, tuple[str, ...]]]:
+    """Return components paired with dotted-name path parts."""
+    result: list[tuple[Component, tuple[str, ...]]] = []
+
+    def visit(component: Component, path: tuple[str, ...]) -> None:
+        current_path = path + (component.name,)
+        result.append((component, current_path))
+        if isinstance(component.implementation, GraphImplementation):
+            for child in component.implementation.graph.components.values():
+                visit(child, current_path)
+
+    visit(root, prefix)
+    return result
+
+
+def _find_component(
+    document: Document,
+    requested_path: str,
+) -> tuple[ComponentID, Component, tuple[str, ...]]:
+    """Find a component by its dotted name path."""
+    matches: list[tuple[ComponentID, Component, tuple[str, ...]]] = []
+    for root_id, root in document.root.items():
+        for component, path in _component_paths(root):
+            if ".".join(path) == requested_path:
+                matches.append((root_id, component, path))
+
+    if len(matches) == 1:
+        return matches[0]
+    if not matches:
+        raise ValueError(f"component path {requested_path!r} was not found")
+    raise ValueError(f"component path {requested_path!r} is ambiguous")
+
+
+def _nodes(
+    network: BondGraphNetwork,
+    node_ids: dict[int, str],
+    paths: list[tuple[Component, tuple[str, ...]]],
+) -> list[str]:
+    path_by_component = {
+        id(component): ".".join(path)
+        for component, path in paths
+    }
+    return [
+        "  "
+        + _quote(node_ids[id(component)])
+        + " [label="
+        + _quote(component.name)
+        + ", xlabel="
+        + _quote(path_by_component[id(component)])
+        + "];"
+        for component in network.components
+    ]
+
+
+def _bonds(
+    network: BondGraphNetwork,
+    node_ids: dict[int, str],
+) -> list[str]:
+    lines = []
+    for bond in network.bonds:
+        attributes = {
+            "arrowhead": "halfopen",
+            "taillabel": bond.source.port.name,
+            "headlabel": bond.target.port.name,
+            "labeldistance": "1.5",
+        }
+        if bond.connection.causality is BondCausality.EFFORT_OUT:
+            attributes["arrowhead"] = "teehalfopen"
+        elif bond.connection.causality is BondCausality.FLOW_OUT:
+            attributes.update(dir="both", arrowtail="tee")
+        if bond.connection.undesired:
+            attributes.update(color="red", style="dashed")
+
+        source = _quote(node_ids[id(bond.source.component)])
+        target = _quote(node_ids[id(bond.target.component)])
+        rendered = ", ".join(
+            f"{name}={_quote(value)}"
+            for name, value in attributes.items()
+        )
+        lines.append(f"  {source} -> {target} [{rendered}];")
+    return lines
+
+
+def _quote(value: object) -> str:
+    """Quote a value as a DOT string."""
+    return json.dumps(str(value), ensure_ascii=False)
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())