Merge branch 'main' into edi_dev

.coin-or/projDesc.xml

@@ -287,7 +287,7 @@ Carl D. Laird, Chair, Pyomo Management Committee, claird at andrew dot cmu dot e
 
 			<platform>
 				<operatingSystem>Any</operatingSystem>
-				<compiler>Python 3.8, 3.9, 3.10, 3.11, 3.12, 3.13</compiler>
+				<compiler>Python 3.9, 3.10, 3.11, 3.12, 3.13</compiler>
 			</platform>
 
 		</testedPlatforms>

.github/workflows/release_wheel_creation.yml

@@ -29,12 +29,9 @@ jobs:
       matrix:
         os: [ubuntu-22.04, windows-latest, macos-latest]
         arch: [all]
-        wheel-version: ['cp38*', 'cp39*', 'cp310*', 'cp311*', 'cp312*', 'cp313*']
+        wheel-version: ['cp39*', 'cp310*', 'cp311*', 'cp312*', 'cp313*']
 
         include:
-        - wheel-version: 'cp38*'
-          TARGET: 'py38'
-          GLOBAL_OPTIONS: "--with-cython --with-distributable-extensions"
         - wheel-version: 'cp39*'
           TARGET: 'py39'
           GLOBAL_OPTIONS: "--with-cython --with-distributable-extensions"
@@ -96,12 +93,9 @@ jobs:
       matrix:
         os: [ubuntu-22.04]
         arch: [all]
-        wheel-version: ['cp38*', 'cp39*', 'cp310*', 'cp311*', 'cp312*', 'cp313*']
+        wheel-version: ['cp39*', 'cp310*', 'cp311*', 'cp312*', 'cp313*']
 
         include:
-        - wheel-version: 'cp38*'
-          TARGET: 'py38'
-          GLOBAL_OPTIONS: "--with-cython --with-distributable-extensions"
         - wheel-version: 'cp39*'
           TARGET: 'py39'
           GLOBAL_OPTIONS: "--with-cython --with-distributable-extensions"
@@ -185,7 +179,7 @@ jobs:
         include:
         - os: ubuntu-latest
           TARGET: generic_tarball
-        python-version: [3.8]
+        python-version: [3.9]
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}

.github/workflows/test_branches.yml

@@ -75,20 +75,14 @@ jobs:
         other: [""]
         category: [""]
 
-        # win/3.8 conda builds no longer work due to environment not being able
-        # to resolve. We are skipping it now.
-        exclude:
-        - os: windows-latest
-          python: 3.8
-
         include:
         - os: ubuntu-latest
           python: '3.13'
           TARGET: linux
           PYENV: pip
 
         - os: macos-latest
-          python: '3.10'
+          python: '3.11'
           TARGET: osx
           PYENV: pip
 
@@ -125,7 +119,7 @@ jobs:
           PACKAGES: cython
 
         - os: windows-latest
-          python: 3.8
+          python: '3.10'
           other: /pip
           skip_doctest: 1
           TARGET: win
@@ -693,17 +687,17 @@ jobs:
 
 
   bare-python-env:
-    name: linux/3.8/bare-env
+    name: linux/3.9/bare-env
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
     - name: Checkout Pyomo source
       uses: actions/checkout@v4
 
-    - name: Set up Python 3.8
+    - name: Set up Python 3.9
       uses: actions/setup-python@v5
       with:
-        python-version: 3.8
+        python-version: 3.9
 
     - name: Install Pyomo
       run: |
@@ -761,17 +755,17 @@ jobs:
     #  id: pip-cache
     #  with:
     #    path: cache/pip
-    #    key: pip-${{env.CACHE_VER}}.0-${{runner.os}}-3.8
+    #    key: pip-${{env.CACHE_VER}}.0-${{runner.os}}-3.9
 
     - name: Download build artifacts
       uses: actions/download-artifact@v4
       with:
         path: artifacts
 
-    - name: Set up Python 3.8
+    - name: Set up Python 3.9
       uses: actions/setup-python@v5
       with:
-        python-version: 3.8
+        python-version: 3.9
 
     - name: Install Python Packages (pip)
       shell: bash # DO NOT REMOVE: see note above

.github/workflows/test_pr_and_main.yml

@@ -68,16 +68,10 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python: [ 3.8, 3.9, '3.10', '3.11', '3.12', '3.13' ]
+        python: [ 3.9, '3.10', '3.11', '3.12', '3.13' ]
         other: [""]
         category: [""]
 
-        # win/3.8 conda builds no longer work due to environment not being able
-        # to resolve. We are skipping it now.
-        exclude:
-        - os: windows-latest
-          python: 3.8
-
         include:
         - os: ubuntu-latest
           TARGET: linux
@@ -119,7 +113,7 @@ jobs:
           PACKAGES: cython
 
         - os: windows-latest
-          python: 3.8
+          python: 3.9
           other: /pip
           skip_doctest: 1
           TARGET: win
@@ -134,7 +128,7 @@ jobs:
           PYENV: pip
 
         - os: ubuntu-latest
-          python: 3.8
+          python: 3.9
           other: /slim
           slim: 1
           skip_doctest: 1
@@ -151,7 +145,7 @@ jobs:
           PACKAGES: "gurobipy dill numpy>2.0 scipy networkx"
 
         - os: ubuntu-latest
-          python: 3.9
+          python: '3.10'
           other: /pyutilib
           TARGET: linux
           PYENV: pip
@@ -727,18 +721,18 @@ jobs:
 
 
   bare-python-env:
-    name: linux/3.8/bare-env
+    name: linux/3.9/bare-env
     needs: lint  # the linter job is a prerequisite for PRs
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
     - name: Checkout Pyomo source
       uses: actions/checkout@v4
 
-    - name: Set up Python 3.8
+    - name: Set up Python 3.9
       uses: actions/setup-python@v5
       with:
-        python-version: 3.8
+        python-version: 3.9
 
     - name: Install Pyomo
       run: |
@@ -796,17 +790,17 @@ jobs:
     #  id: pip-cache
     #  with:
     #    path: cache/pip
-    #    key: pip-${{env.CACHE_VER}}.0-${{runner.os}}-3.8
+    #    key: pip-${{env.CACHE_VER}}.0-${{runner.os}}-3.9
 
     - name: Download build artifacts
       uses: actions/download-artifact@v4
       with:
         path: artifacts
 
-    - name: Set up Python 3.8
+    - name: Set up Python 3.9
       uses: actions/setup-python@v5
       with:
-        python-version: 3.8
+        python-version: 3.9
 
     - name: Install Python Packages (pip)
       shell: bash # DO NOT REMOVE: see note above

README.md

@@ -52,7 +52,7 @@ Pyomo is available under the BSD License - see the
 
 Pyomo is currently tested with the following Python implementations:
 
-* CPython: 3.8, 3.9, 3.10, 3.11, 3.12, 3.13
+* CPython: 3.9, 3.10, 3.11, 3.12, 3.13
 * PyPy: 3.9
 
 _Testing and support policy_:

doc/OnlineDocs/getting_started/installation.rst

@@ -5,7 +5,7 @@ Installation
 
 Pyomo currently supports the following versions of Python:
 
-* CPython: 3.8, 3.9, 3.10, 3.11, 3.12, 3.13
+* CPython: 3.9, 3.10, 3.11, 3.12, 3.13
 * PyPy: 3
 
 At the time of the first Pyomo release after the end-of-life of a minor Python

pyomo/common/dependencies.py

@@ -11,6 +11,7 @@
 
 import inspect
 import importlib
+import importlib.util
 import logging
 import sys
 import warnings
@@ -520,13 +521,22 @@ def find_spec(self, fullname, path, target=None):
 
         spec = None
         # Continue looking for the finder that would have originally
-        # loaded the deferred import module b starting at the next
+        # loaded the deferred import module by starting at the next
         # finder in sys.meta_path (this way, we are agnostic to where
         # the module is coming from: file system, registry, etc.)
         for finder in sys.meta_path[sys.meta_path.index(self) + 1 :]:
-            spec = finder.find_spec(fullname, path, target)
-            if spec is not None:
-                break
+            if hasattr(finder, 'find_spec'):
+                # Support standard importlib MetaPathFinders
+                spec = finder.find_spec(fullname, path, target)
+                if spec is not None:
+                    break
+            else:
+                # Support for imp finders/loaders (deprecated, but
+                # supported through Python 3.11)
+                loader = finder.find_module(fullname, path)
+                if loader is not None:
+                    spec = importlib.util.spec_from_loader(fullname, loader)
+                    break
         else:
             # Module not found.  Returning None will proceed to the next
             # finder (which will eventually raise a ModuleNotFoundError)

pyomo/common/tests/mod.py

@@ -0,0 +1,17 @@
+#  ___________________________________________________________________________
+#
+#  Pyomo: Python Optimization Modeling Objects
+#  Copyright (c) 2008-2024
+#  National Technology and Engineering Solutions of Sandia, LLC
+#  Under the terms of Contract DE-NA0003525 with National Technology and
+#  Engineering Solutions of Sandia, LLC, the U.S. Government retains certain
+#  rights in this software.
+#  This software is distributed under the 3-clause BSD License.
+#  ___________________________________________________________________________
+#
+
+# This is a simple module used as part of testing import callbacks
+
+
+class Foo(object):
+    data = 42

pyomo/common/tests/test_dependencies.py

@@ -10,6 +10,8 @@
 #  ___________________________________________________________________________
 
 import inspect
+import sys
+from importlib.machinery import PathFinder
 from io import StringIO
 
 import pyomo.common.unittest as unittest
@@ -24,6 +26,7 @@
     UnavailableClass,
     _DeferredAnd,
     _DeferredOr,
+    _DeferredImportCallbackFinder,
     check_min_version,
     dill,
     dill_available,
@@ -248,6 +251,70 @@ def _record_avail(module, avail):
         self.assertFalse(avail1)
         self.assertEqual(ans, [True, False])
 
+    def test_callback_on_import(self):
+        sys.modules.pop('pyomo.common.tests.mod', None)
+        ans = []
+
+        class ImpFinder(object):
+            # This is an "imp" module-style finder (deprecated in Python
+            # 3.4 and removed in Python 3.12, but Google Collab still
+            # defines finders like this)
+            match = ''
+
+            def find_module(self, fullname, path=None):
+                if fullname != self.match:
+                    ans.append('pass')
+                    return None
+                ans.append('load')
+                spec = PathFinder().find_spec(fullname, path)
+                return spec.loader
+
+            def load_module(self, name):
+                pass
+
+        def _callback(module, avail):
+            ans.append(len(ans))
+
+        attempt_import('pyomo.common.tests.mod', defer_import=True, callback=_callback)
+        self.assertEqual(ans, [])
+        import pyomo.common.tests.mod as m
+
+        self.assertEqual(ans, [0])
+        self.assertEqual(m.Foo.data, 42)
+
+        sys.modules.pop('pyomo.common.tests.mod', None)
+        del m
+        attempt_import('pyomo.common.tests.mod', defer_import=True, callback=_callback)
+
+        try:
+            # Test deferring to an imp-style finder that does not match
+            # the target module name
+            _finder = ImpFinder()
+            sys.meta_path.insert(
+                sys.meta_path.index(_DeferredImportCallbackFinder) + 1, _finder
+            )
+            import pyomo.common.tests.mod as m
+
+            self.assertEqual(ans, [0, 'pass', 2])
+            self.assertEqual(m.Foo.data, 42)
+
+            sys.modules.pop('pyomo.common.tests.mod', None)
+            del m
+            attempt_import(
+                'pyomo.common.tests.mod', defer_import=True, callback=_callback
+            )
+
+            # Test deferring to an imp-style finder that DOES match the
+            # target module name
+            _finder.match = 'pyomo.common.tests.mod'
+
+            import pyomo.common.tests.mod as m
+
+            self.assertEqual(ans, [0, 'pass', 2, 'load', 4])
+            self.assertEqual(m.Foo.data, 42)
+        finally:
+            sys.meta_path.remove(_finder)
+
     def test_import_exceptions(self):
         mod, avail = attempt_import(
             'pyomo.common.tests.dep_mod_except',

setup.py

@@ -234,7 +234,6 @@ def __ne__(self, other):
         'Operating System :: Unix',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: 3.11',
@@ -245,7 +244,7 @@ def __ne__(self, other):
         'Topic :: Scientific/Engineering :: Mathematics',
         'Topic :: Software Development :: Libraries :: Python Modules',
     ],
-    python_requires='>=3.8',
+    python_requires='>=3.9',
     install_requires=['ply'],
     extras_require={
         # There are certain tests that also require pytest-qt, but because those