FIX: implement correct latex repr method name (#393)

* ENH: check for `_latex_repr_` typo
* MAINT: write latex test for `InvariantMass`

src/ampform/kinematics/lorentz.py

@@ -131,7 +131,7 @@ class EuclideanNorm(NumPyPrintable):
     """Take the euclidean norm of an array over axis 1."""
 
     vector: sp.Basic
-    _latex_repr = R"\left|{vector}\right|"
+    _latex_repr_ = R"\left|{vector}\right|"
 
     def evaluate(self) -> ArraySlice:
         return sp.sqrt(EuclideanNormSquared(self.vector))
@@ -163,7 +163,7 @@ class InvariantMass(sp.Expr):
     """Invariant mass of a `.FourMomentumSymbol`."""
 
     momentum: sp.Basic
-    _latex_repr = "m_{{{momentum}}}"
+    _latex_repr_ = "m_{{{momentum}}}"
 
     def evaluate(self) -> ComplexSqrt:
         p = self.momentum
@@ -176,7 +176,7 @@ class NegativeMomentum(sp.Expr):
     r"""Invert the spatial components of a `.FourMomentumSymbol`."""
 
     momentum: sp.Basic
-    _latex_repr = R"-\left({momentum}\right)"
+    _latex_repr_ = R"-\left({momentum}\right)"
 
     def evaluate(self) -> sp.Expr:
         p = self.momentum
@@ -261,7 +261,7 @@ class _BoostZMatrixImplementation(NumPyPrintable):
     gamma_beta: sp.Basic
     ones: _OnesArray
     zeros: _ZerosArray
-    _latex_repr = R"\boldsymbol{{B_z}}\left({beta}\right)"
+    _latex_repr_ = R"\boldsymbol{{B_z}}\left({beta}\right)"
 
     def _numpycode(self, printer: NumPyPrinter, *args) -> str:
         printer.module_imports[printer._module].add("array")
@@ -281,7 +281,7 @@ class BoostMatrix(sp.Expr):
     r"""Compute a rank-3 Lorentz boost matrix from a `.FourMomentumSymbol`."""
 
     momentum: sp.Basic
-    _latex_repr = R"\boldsymbol{{B}}\left({momentum}\right)"
+    _latex_repr_ = R"\boldsymbol{{B}}\left({momentum}\right)"
 
     def as_explicit(self) -> sp.MutableDenseMatrix:
         momentum = self.momentum
@@ -349,7 +349,7 @@ class _BoostMatrixImplementation(NumPyPrintable):
     b22: sp.Basic
     b23: sp.Basic
     b33: sp.Basic
-    _latex_repr = R"\boldsymbol{{B}}\left({momentum}\right)"
+    _latex_repr_ = R"\boldsymbol{{B}}\left({momentum}\right)"
 
     def _numpycode(self, printer: NumPyPrinter, *args) -> str:
         _, b00, b01, b02, b03, b11, b12, b13, b22, b23, b33 = self.args
@@ -405,7 +405,7 @@ class _RotationYMatrixImplementation(NumPyPrintable):
     sin_angle: sp.Basic
     ones: _OnesArray
     zeros: _ZerosArray
-    _latex_repr = R"\boldsymbol{{R_y}}\left({angle}\right)"
+    _latex_repr_ = R"\boldsymbol{{R_y}}\left({angle}\right)"
 
     def _numpycode(self, printer: NumPyPrinter, *args) -> str:
         printer.module_imports[printer._module].add("array")
@@ -462,7 +462,7 @@ class _RotationZMatrixImplementation(NumPyPrintable):
     sin_angle: sp.Basic
     ones: _OnesArray
     zeros: _ZerosArray
-    _latex_repr = R"\boldsymbol{{R_z}}\left({angle}\right)"
+    _latex_repr_ = R"\boldsymbol{{R_z}}\left({angle}\right)"
 
     def _numpycode(self, printer: NumPyPrinter, *args) -> str:
         printer.module_imports[printer._module].add("array")

src/ampform/sympy/_decorator.py

@@ -344,10 +344,15 @@ def __call__(self, printer: LatexPrinter, *args) -> str: ...
 
 @dataclass_transform(field_specifiers=(argument, _create_field))
 def _implement_latex_repr(cls: type[T]) -> type[T]:
-    _latex_repr_: LatexMethod | str | None = getattr(cls, "_latex_repr_", None)
+    repr_name = "_latex_repr_"
+    repr_mistyped = "_latex_repr"
+    if hasattr(cls, repr_mistyped):
+        msg = f"Class defines a {repr_mistyped} attribute, but it should be {repr_name}"
+        raise AttributeError(msg)
+    _latex_repr_: LatexMethod | str | None = getattr(cls, repr_name, None)
     if _latex_repr_ is None:
         msg = (
-            "You need to define a _latex_repr_ str or method in order to decorate an"
+            f"You need to define a {repr_name} str or method in order to decorate an"
             " unevaluated expression with a printer method for LaTeX representation."
         )
         raise NotImplementedError(msg)

tests/kinematics/test_lorentz.py

@@ -193,6 +193,12 @@ def test_latex(self):
 
 
 class TestInvariantMass:
+    def test_latex(self):
+        p = FourMomentumSymbol("p1", shape=[])
+        mass = InvariantMass(p)
+        latex = sp.latex(mass)
+        assert latex == "m_{p_{1}}"
+
     @pytest.mark.parametrize(
         ("state_id", "expected_mass"),
         [