Header of process and node ports follow each other both ways: a panel edit rewrites only the def line of edited code, a code save reads the header back into input ports and settings (draft and response); Space types in the node editor again

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

backend/tests/flow/test_node_settings.py

@@ -9,7 +9,7 @@ from pathlib import Path
 
 import pytest
 
-from fluksio.flow.controller import FlowController
+from fluksio.flow.controller import FlowController, follow_header
 from fluksio.flow.messages import DType, MessageSpec
 from fluksio.flow.pipeline import Pipeline
 from fluksio.flow.schemas import FlowDef, NodeDef
@@ -148,3 +148,66 @@ def test_a_shared_body_is_checked_against_each_user(store: FlowStore):
 
     assert [n.status for n in nodes] == ["error"]
     assert "'level' is an input of 'scale'" in (nodes[0].error or "")
+
+
+def _scaffold_header(node: NodeDef) -> str:
+    """The header the canvas writes: input ports in order, then settings."""
+    names = [spec.port for spec in node.requires] + [
+        key for key in node.params if key != "synchronous"
+    ]
+    return f"def process({', '.join(names)}):\n    return {{}}\n"
+
+
+def test_a_scaffold_header_reads_back_as_the_node_it_came_from():
+    node = _flow(
+        [*READING, MessageSpec(name="garden.level", port="depth")],
+        factor=3,
+        synchronous=True,
+    ).nodes[0]
+
+    assert follow_header(node, _scaffold_header(node)) == node
+
+
+def test_a_header_declares_ports_and_settings_that_read_back_the_same():
+    header = "def process(reading, level, gain=1.5, mode='eco'):\n    return {}\n"
+
+    node = follow_header(_flow([]).nodes[0], header)
+
+    assert [spec.port for spec in node.requires] == ["reading", "level"]
+    assert node.params == {"gain": 1.5, "mode": "eco"}
+    assert _scaffold_header(node).split(":")[0] == (
+        "def process(reading, level, gain, mode)"
+    )
+
+
+def test_a_renamed_parameter_keeps_the_message_and_a_dropped_one_goes():
+    node = _flow(READING, factor=3, offset=1).nodes[0]
+
+    renamed = follow_header(node, "def process(value, factor, offset): pass\n")
+    dropped = follow_header(node, "def process(reading, factor): pass\n")
+
+    assert renamed.requires == [READING[0].model_copy(update={"port": "value"})]
+    assert renamed.params == {"factor": 3, "offset": 1}
+    assert dropped.requires == READING
+    assert dropped.params == {"factor": 3}
+
+
+def test_a_new_parameter_after_a_setting_is_a_setting():
+    node = _flow(READING, factor=3).nodes[0]
+
+    followed = follow_header(node, "def process(reading, factor, offset): pass\n")
+
+    assert followed.requires == READING
+    assert followed.params == {"factor": 3, "offset": ""}
+
+
+def test_a_header_it_cannot_read_for_certain_leaves_the_node():
+    node = _flow(READING, factor=3).nodes[0]
+
+    for code in (
+        "def process(reading, factor",
+        "def process(**kw): pass\n",
+        "@cache\ndef process(value): pass\n",
+        "def run(value): pass\n",
+    ):
+        assert follow_header(node, code) == node