Fix manually set default importances not printed

doc/source/changelog.rst

@@ -11,6 +11,7 @@ MontePy Changelog
 **Bugs Fixed**
 
 * Fixed a bug where ``append_renumber`` raised a ``TypeError`` when called with an object whose ``number`` is ``None`` (e.g. an object created with no arguments) (:issue:`880`).
+* Fixed a bug where the importance of cells made from scratch are usually not printed to the output file (:pull:`921`).
 
 **Feature Added**
 

montepy/data_inputs/importance.py

@@ -3,6 +3,8 @@
 import copy
 import math
 import warnings
+
+import montepy
 from montepy.data_inputs.cell_modifier import CellModifierInput, InitInput
 from montepy.exceptions import *
 from montepy.constants import DEFAULT_VERSION, rel_tol, abs_tol
@@ -133,7 +135,8 @@ def has_information(self):
         has_info = []
         for part in self:
             has_info.append(
-                not math.isclose(
+                self._explicitly_set
+                or not math.isclose(
                     self[part], self._DEFAULT_IMP, rel_tol=rel_tol, abs_tol=abs_tol
                 )
             )
@@ -244,7 +247,9 @@ def _format_tree(self):
             particles_printed = set()
             ret = ""
             for particle in self:
-                if particle in particles_printed:
+                if particle in particles_printed or (
+                    self._problem and particle not in self._problem.mode
+                ):
                     continue
                 other_particles = self._particle_importances[particle][
                     "classifier"
@@ -299,10 +304,13 @@ def all(self, value):
         value = float(value)
         if value < 0.0:
             raise ValueError("Importance must be ≥ 0.0")
+        self._explicitly_set = True
         if self._problem:
-            self._explicitly_set = True
             for particle in self._problem.mode:
                 self._particle_importances[particle]["data"][0].value = value
+        else:
+            for particle in montepy.Particle:
+                self[particle] = value
 
     def _clear_data(self):
         if not self.in_cell_block:

tests/test_importance.py

@@ -2,6 +2,7 @@
 import montepy
 import os
 import io
+from pathlib import Path
 import pytest
 from montepy.cell import Cell
 from montepy.particle import Particle
@@ -317,3 +318,48 @@ def test_default_cell_importance(self):
         """Test that new cells have default importance of 1.0 (Issue #735)"""
         cell = montepy.Cell()
         assert cell.importance.neutron == 1.0
+
+    def test_print_explicit_default_imp(_):  # based on #892
+        problem = montepy.read_input(Path("tests") / "inputs" / "test.imcnp")
+
+        # Modify an existing cell. Importance remains.
+        problem.cells[1].geometry &= +problem.surfaces[1000]
+        # Cell 2 should give "imp:n=2.0 imp:p=2.0"
+        c2 = montepy.Cell(number=4)
+        c2.geometry = -problem.surfaces[1000] & +problem.surfaces[1005]
+        c2.importance.all = 2.0
+        problem.cells.append(c2)
+        # Cell 3 should give "imp:n=1.0 imp:p=1.0"
+        c3 = montepy.Cell(number=6)
+        c3.geometry = -problem.surfaces[1005] & +problem.surfaces[1010]
+        c3.importance.neutron = 1.0
+        c3.importance.photon = 1.0
+        problem.cells.append(c3)
+        # Cell 4 should give "imp:n=4.0 imp:p=1.0"
+        c4 = montepy.Cell(number=7)
+        c4.geometry = -problem.surfaces[1010]
+        c4.importance.neutron = 4.0
+        problem.cells.append(c4)
+        # Cell 5 DOES give "imp:n=5.0 imp:p=1.0"
+        c5 = montepy.Cell(number=8)
+        c5.geometry = -problem.surfaces[1015]
+        c5.importance.neutron = 5.0
+        c5.importance.photon = 1.0
+        problem.cells.append(c5)
+        # Ensure that this is set:
+        # Ensure that this is set:
+        problem.print_in_data_block["imp"] = False
+
+        stream = io.StringIO()
+        problem.write_problem(stream)
+        stream.seek(0)
+        new_problem = montepy.read_input(stream)
+        stream.close()
+        cells = new_problem.cells
+        for cell_num, imp_str in {
+            4: "IMP:n=2.0 IMP:p=2.0",
+            6: "IMP:n=1.0 IMP:p=1.0",
+            7: "IMP:n=4.0 IMP:p=1.0",
+            8: "IMP:n=5.0 IMP:p=1.0",
+        }.items():
+            assert imp_str in cells[cell_num]._input.input_text

tests/test_universe_integration.py

@@ -120,7 +120,7 @@ def test_fill_multi_universe_order(cells):
         output = cell.format_for_mcnp_input((6, 2, 0))
         words = " ".join(output).split()
         start_idx = 6
-        if "imp:n=1" in words:
+        if "imp" in words[3].lower():
             start_idx += 1
         print(output)
         new_universes = list(map(int, words[start_idx:]))