FIX: allow generating empty phase space samples (#465)

* FIX: update PR labels
* MAINT: add test for generating empty phase space sample

.github/workflows/pr-linting.yml

@@ -18,15 +18,16 @@ jobs:
     steps:
       - uses: docker://agilepathway/pull-request-label-checker:latest
         with:
-          any_of: Bug,💡 Feature,⚠️ Interface,📝 Docs,🔨 Maintenance,🖱️ DX
-          none_of: Epic,❌ Won't fix,💫 Good first issue
+          any_of:
+            🐛 Bug,💡 Feature,⚙️ Enhancement,⚠️ Interface,❗ Behavior,📝 Docs,🔨
+            Maintenance,🖱️ DX
+          none_of: Epic,💫 Good first issue
           repo_token: ${{ secrets.GITHUB_TOKEN }}
 
   check-title:
     name: Check title
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v1
-      - name: Install Dependencies
-        run: npm install @commitlint/config-conventional
+      - run: npm install @commitlint/config-conventional
       - uses: JulienKode/pull-request-name-linter-action@v0.5.0

src/tensorwaves/data/phasespace.py

@@ -72,7 +72,8 @@ def generate(self, size: int, rng: RealNumberGenerator) -> DataSample:
             progress_bar.update(n=get_number_of_events(bunch))
         finalize_progress_bar(progress_bar)
         phsp = select_events(momentum_pool, selector=slice(None, size))
-        del phsp["weights"]
+        if len(phsp) != 0:
+            del phsp["weights"]
         return phsp
 
 

tests/data/test_phasespace.py

@@ -124,6 +124,17 @@ def test_generate(
             assert len(momenta) == n_events
             assert pytest.approx(momenta, abs=1e-6) == expected_sample[i]
 
+    def test_generate_no_events(self, pdg: "ParticleCollection"):
+        rng = TFUniformRealNumberGenerator()
+        phsp_generator = TFPhaseSpaceGenerator(
+            initial_state_mass=pdg["J/psi(1S)"].mass,
+            final_state_masses={
+                i: pdg[name].mass for i, name in enumerate(["gamma", "pi0", "pi0"])
+            },
+        )
+        phsp_momenta = phsp_generator.generate(0, rng)
+        assert len(phsp_momenta) == 0
+
 
 class TestTFWeightedPhaseSpaceGenerator:
     def test_generate_deterministic(self, pdg: "ParticleCollection"):