dotbot/calibration: name the spin calibration to append to instead of a placed one

dotbot/calibration/conics.py

@@ -690,6 +690,8 @@ def field_angle(centres: np.ndarray) -> float:
 
 # What a free-mode calibration records as its site's anchor: no mark in the
 # room is its origin.
+# A site made by `site init` records the calibration it came from in its anchor
+SELF_DEFINED_ANCHOR = "self-defined from spin calibration "
 FREE_FRAME_ANCHOR = (
     "free mode: zero at the top-left of the rectangle around the spinning "
     "robots, grown by a robot's footprint; axes along that rectangle"
@@ -822,7 +824,7 @@ def self_defined_site(
     extent, field_area, staging = starter_layout((field_w, field_h), size_mm)
     dx, dy = field_area.x, field_area.y
     shift = np.array([[1, 0, dx], [0, 1, dy], [0, 0, 1.0]])
-    anchor = f"self-defined from spin calibration {calibration.id8}"
+    anchor = f"{SELF_DEFINED_ANCHOR}{calibration.id8}"
     stations = []
     for st in calibration.stations:
         H = shift @ st.matrix
@@ -853,5 +855,6 @@ def self_defined_site(
         created_at=calibration.created_at,
         tag=f"{calibration.tag}-{name}" if calibration.tag else "",
         robot=calibration.robot,
+        placed_from=calibration.id,
     )
     return site, placed

dotbot/calibration/lighthouse2.py

@@ -257,6 +257,8 @@ class Calibration:
     created_at: str = ""
     tag: str = ""
     robot: str = ROBOT_DEFAULT
+    # The id of the free-frame spin calibration this one was moved from
+    placed_from: str = ""
     path: Optional[Path] = None
     # The id the file on disk declares, when this came from one. A mismatch
     # with `id` means the file was hand-edited into a different calibration.
@@ -686,6 +688,8 @@ def render_calibration(calibration: Calibration) -> str:
     ]
     if calibration.tag:
         out.append(f'tag = "{toml_escape(calibration.tag)}"')
+    if calibration.placed_from:
+        out.append(f'placed_from = "{calibration.placed_from}"')
     out += [
         "",
         "[site]",
@@ -867,6 +871,7 @@ def read_calibration_file(path: Path) -> Calibration:
         created_at=metadata.get("created_at", ""),
         tag=metadata.get("tag", ""),
         robot=metadata.get("robot", ROBOT_DEFAULT),
+        placed_from=str(metadata.get("placed_from", "")),
         path=path,
     )
     calibration.stored_id = str(metadata.get("id", ""))
@@ -1043,6 +1048,15 @@ def _file_metadata(path: Path) -> dict:
         return {}
 
 
+def calibration_site_of(spec: str) -> Optional[str]:
+    """The site of the one calibration file under any site that `spec`
+    names, None when none or several do."""
+    try:
+        return read_calibration_file(resolve_calibration_path(spec)).site.name
+    except (OSError, ValueError):
+        return None
+
+
 def load_calibration(
     spec: str,
     root: Optional[Path] = None,

dotbot/calibration/multi_station.py

@@ -1174,17 +1174,33 @@ def appendable_rounds(calibration: Calibration) -> int:
     calibration is in a frame a re-solve would not keep.
     """
     # pylint: disable=import-outside-toplevel
-    from dotbot.calibration.conics import FREE_FRAME_ANCHOR
+    from dotbot.calibration.conics import FREE_FRAME_ANCHOR, SELF_DEFINED_ANCHOR
+    from dotbot.calibration.lighthouse2 import calibration_site_of
 
     if (
         not calibration.tracks
         or calibration.site.anchor != FREE_FRAME_ANCHOR
         or not all(st.solved_from.startswith("conics") for st in calibration.stations)
     ):
-        raise ValueError(
+        refused = (
             f"calibration {calibration.id8} is not a free-mode spin calibration, "
-            "so a round cannot be appended to it; append to the spin calibration "
-            "it was made from"
+            "so a round cannot be appended to it"
+        )
+        anchor = calibration.site.anchor
+        if calibration.placed_from:
+            source = calibration.placed_from
+            how = f"it was placed from spin calibration {source[:8]}"
+        elif anchor.startswith(SELF_DEFINED_ANCHOR):
+            source = anchor[len(SELF_DEFINED_ANCHOR) :].strip()
+            how = f"its site was defined from spin calibration {source[:8]}"
+        else:
+            raise ValueError(
+                f"{refused}; append to the spin calibration it was made from"
+            )
+        where = calibration_site_of(source)
+        raise ValueError(
+            f"{refused}: {how}, so append to that one"
+            + (f" (--append {source[:8]} --site {where})" if where else "")
         )
     return max(t.round for t in calibration.tracks) + 1
 

dotbot/tests/test_calibration_spin.py

@@ -18,6 +18,7 @@
 from dotbot.calibration import conics, lighthouse2, push
 from dotbot.calibration import spin as spin_module
 from dotbot.calibration.lighthouse2 import counts_for_camera_point, load_calibration
+from dotbot.calibration.multi_station import appendable_rounds
 from dotbot.calibration.spin import (
     SPIN_CHUNK_RECORDS,
     SPIN_TAG,
@@ -746,6 +747,46 @@ def test_append_refuses_a_corner_calibration(monkeypatch, lab, tmp_path):
     assert fleet.calls == []
 
 
+def test_append_to_a_placed_calibration_names_the_one_it_came_from(monkeypatch, lab):
+    _, fleet = _fleet()
+    result = _collect(monkeypatch, lab, fleet)
+    free_id = re.search(r"--from-calibration (\w+)", result.output).group(1)
+    result = CliRunner().invoke(
+        site_cmd.cmd,
+        ["init", "spun", "--from-calibration", free_id],
+        obj={"config": lab},
+    )
+    placed_id = re.search(r"push (\w+) --site spun", result.output).group(1)
+    _, fleet = _fleet()
+    result = _collect(monkeypatch, lab, fleet, "--site", "spun", "--append", placed_id)
+    assert result.exit_code != 0
+    assert "not a free-mode spin calibration" in result.output
+    assert f"placed from spin calibration {free_id}" in result.output
+    assert f"--append {free_id} --site c405" in result.output
+    assert fleet.calls == []
+
+
+def test_a_placed_file_without_its_source_falls_back_to_the_site_anchor(
+    monkeypatch, lab
+):
+    _, fleet = _fleet()
+    result = _collect(monkeypatch, lab, fleet)
+    free_id = re.search(r"--from-calibration (\w+)", result.output).group(1)
+    result = CliRunner().invoke(
+        site_cmd.cmd,
+        ["init", "spun", "--from-calibration", free_id],
+        obj={"config": lab},
+    )
+    path = Path(re.search(r"saved to (\S+)", result.output).group(1))
+    text = path.read_text()
+    assert f'placed_from = "{free_id}' in text
+    path.write_text(re.sub(r'placed_from = "\w+"\n', "", text))
+    with pytest.raises(ValueError) as refused:
+        appendable_rounds(lighthouse2.read_calibration_file(path))
+    assert f"its site was defined from spin calibration {free_id}" in str(refused.value)
+    assert f"--append {free_id} --site c405" in str(refused.value)
+
+
 def test_append_and_drop_station_go_with_spin(lab):
     for flags in (["--append", "x"], ["--drop-station", "2"]):
         result = CliRunner().invoke(