fix: Support EnVision calculated formulas without a name prefix (#1246)

## Summary
A PerkinElmer EnVision 384-well absorbance export (`OD450`) failed to
parse:

```
AllotropeConversionError: Unable to find expected formula name for calculated results section.
```

The calculated plate's `Formula` is a plain description with no `name =`
prefix:

```
Calc 1: OD450 direct absorbance value at 450 nm
```

`CalculatedPlateInfo.create` extracted the name with `^([^=]*)=`, which
assumes the standard form `Calc N: <name> = <expression>` and raised
when no `=` was present.

## Fix
When the formula has no `=`, fall back to using the whole formula string
as the calculated data name. Standard formulas are unaffected.

## Changes
- `perkin_elmer_envision_structure.py`: make the formula-name regex
optional with a whole-string fallback.
- Reworked `test_create_calculated_plate_info_with_invalid_formula` →
`test_create_calculated_plate_info_with_formula_without_name` to assert
the fallback.
- Edited the formula in the existing
`PE_Envision_fluorescence_example01.csv` to the no-`=` form (and
regenerated its expected JSON) to exercise the fallback end-to-end.
Other example files retain the standard `name = expression` form, so
both branches stay covered.

## Testing
- All 24 `perkin_elmer_envision` tests pass; `hatch run lint` (ruff,
black, mypy) clean.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: nathan-stender

src/allotropy/parsers/perkin_elmer_envision/perkin_elmer_envision_structure.py

@@ -119,10 +119,12 @@ class CalculatedPlateInfo(PlateInfo):
     def create(data: SeriesData) -> CalculatedPlateInfo:
         formula = data[str, "Formula"]
 
-        name = assert_not_none(
-            search(r"^([^=]*)=", formula),
-            msg="Unable to find expected formula name for calculated results section.",
-        ).group(1)
+        # Standard formulas embed the name before an '=' (e.g.
+        # "Calc 1: General = (X / Y) * Z where ..."). Some formulas are a plain
+        # description with no '=' (e.g. "Calc 1: OD450 direct absorbance value at
+        # 450 nm"), in which case the whole formula string is the name.
+        formula_name_match = search(r"^([^=]*)=", formula)
+        name = formula_name_match.group(1) if formula_name_match else formula
 
         plate_number, barcode = PlateInfo.get_plate_number_and_barcode(data)
 

tests/parsers/perkin_elmer_envision/perkin_elmer_envision_structure_test.py

@@ -345,20 +345,27 @@ def test_create_calculated_plate_info_with_no_formula() -> None:
         CalculatedPlateInfo.create(data)
 
 
-def test_create_calculated_plate_info_with_invalid_formula() -> None:
+def test_create_calculated_plate_info_with_formula_without_name() -> None:
+    # Some formulas are a plain description with no "name =" prefix; the whole
+    # formula string is used as the name.
     data = SeriesData(
         pd.Series(
             {
                 "Plate": "dummy",
                 "Measured height": "0",
-                "Formula": "invalid formula",
+                "Formula": "Calc 1: OD450 direct absorbance value at 450 nm",
                 "Measurement date": "10/13/2022 3:08:06 PM",
             }
         )
     )
-    msg = "Unable to find expected formula name for calculated results section."
-    with pytest.raises(AllotropeConversionError, match=msg):
-        CalculatedPlateInfo.create(data)
+    calculated_plate_info = CalculatedPlateInfo.create(data)
+    assert (
+        calculated_plate_info.name == "Calc 1: OD450 direct absorbance value at 450 nm"
+    )
+    assert (
+        calculated_plate_info.formula
+        == "Calc 1: OD450 direct absorbance value at 450 nm"
+    )
 
 
 def test_create_basic_assay_info() -> None:

tests/parsers/perkin_elmer_envision/testdata/PE_Envision_fluorescence_example01.csv

@@ -1,13 +1,13 @@
 Plate information 
 Plate,Repeat,Barcode,Measured height,Chamber temperature at start,Chamber temperature at end,Humidity at start,Humidity at end,Ambient temperature at start,Ambient temperature at end,Formula,Measurement date,
-1,1,"=""""",N/A,N/A,N/A,N/A,N/A,N/A,N/A,Calc 1: General = (X / Y) * Z where X = AC HTRF Laser [Eu](1) channel 1 window 1  Y = AC HTRF Laser [Eu](1) channel 2 window 1  Z = 10000,10/13/2022 3:08:06 PM,
+1,1,"=""""",N/A,N/A,N/A,N/A,N/A,N/A,N/A,Calc 1: HTRF ratio value for AC HTRF Laser [Eu],10/13/2022 3:08:06 PM,
 
 Background information
 Plate,Label,Result,Signal,Flashes/Time,Meastime,MeasInfo,
 1,AC HTRF Laser [Eu],0,162,50,00:00:00.000,De=1st Ex=Top Em=Top Wdw=1 (14),
 1,AC HTRF Laser [Eu],0,260,50,00:00:00.000,De=2nd Ex=Top Em=Top Wdw=1 (142),
 
-Calculated results: Calc 1: General = (X / Y) * Z where X = AC HTRF Laser [Eu](1) channel 1 window 1  Y = AC HTRF Laser [Eu](1) channel 2 window 1  Z = 10000
+Calculated results: Calc 1: HTRF ratio value for AC HTRF Laser [Eu]
 ,01,02,03,04,05,06,07,08,09,10,11,12,
 A,3912.12920565,3923.92517971,3948.45245355,,3933.03506298,4061.92827247,3996.61746992,,,,,,
 B,2385.72193555,2384.42487617,2396.10683014,,2390.61028269,2396.68321027,2424.70697585,,,,,,
@@ -119,8 +119,8 @@ H,- ,- ,- ,  ,- ,- ,- ,  ,  ,  ,  ,
 Calculations:
 Plate,,,,1
  Formula index,,,,Calc 1
- Formula name,,,,General
- Formula,,,,(X / Y) * Z where X = AC HTRF Laser [Eu](1) channel 1 window 1  Y = AC HTRF Laser [Eu](1) channel 2 window 1  Z = 10000
+ Formula name,,,,HTRF ratio value for AC HTRF Laser [Eu]
+ Formula,,,,HTRF ratio value for AC HTRF Laser [Eu]
 
 Auto export parameters:
 Export format,,,,Plate2