From 7e769e7d15d408b86ac5d28d14c7ced1aacaad1f Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Wed, 22 Jan 2025 23:09:34 +0700
Subject: [PATCH 01/13] Test pip editable install with meson

---
 .github/workflows/ci-meson.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index ab073aae87c..5d7d4b05cd5 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -24,6 +24,7 @@ jobs:
       matrix:
         os: [ubuntu]
         python: ['3.11', '3.12']
+        editable: [false, true]
 
     steps:
       - uses: actions/checkout@v4
@@ -70,7 +71,7 @@ jobs:
           export CC="ccache $CC"
           export CXX="ccache $CXX"
           # Use --no-deps and pip check below to verify that all necessary dependencies are installed via conda
-          pip install --no-build-isolation --no-deps --config-settings=builddir=builddir . -v
+          pip install --no-build-isolation --no-deps --config-settings=builddir=builddir ${{ matrix.editable == 'true' && '--editable' || '' }} . -v
 
       - name: Verify dependencies
         shell: bash -l {0}

From fc4d1a3b434e522826770182eea61974218f64e7 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Wed, 22 Jan 2025 23:14:33 +0700
Subject: [PATCH 02/13] Add editable status to name

---
 .github/workflows/ci-meson.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 5d7d4b05cd5..125fe792ee3 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -16,7 +16,7 @@ concurrency:
 
 jobs:
   test:
-    name: Conda (${{ matrix.os }}, Python ${{ matrix.python }})
+    name: Conda (${{ matrix.os }}, Python ${{ matrix.python }}, editable: ${{ matrix.editable }})
     runs-on: ${{ matrix.os }}-latest
 
     strategy:

From 99e92212ecfb32b2c9dc2c333310e343fb1ad3a1 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Wed, 22 Jan 2025 23:14:54 +0700
Subject: [PATCH 03/13] Fix bug?

---
 .github/workflows/ci-meson.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 125fe792ee3..42bb3dfe902 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -71,7 +71,7 @@ jobs:
           export CC="ccache $CC"
           export CXX="ccache $CXX"
           # Use --no-deps and pip check below to verify that all necessary dependencies are installed via conda
-          pip install --no-build-isolation --no-deps --config-settings=builddir=builddir ${{ matrix.editable == 'true' && '--editable' || '' }} . -v
+          pip install --no-build-isolation --no-deps --config-settings=builddir=builddir ${{ matrix.editable && '--editable' || '' }} . -v
 
       - name: Verify dependencies
         shell: bash -l {0}

From ec4531f73a44eb5afe8ed79350222557c6ec2094 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Wed, 22 Jan 2025 23:17:25 +0700
Subject: [PATCH 04/13] Fix another bug

---
 .github/workflows/ci-meson.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 42bb3dfe902..6d82586663d 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -16,7 +16,7 @@ concurrency:
 
 jobs:
   test:
-    name: Conda (${{ matrix.os }}, Python ${{ matrix.python }}, editable: ${{ matrix.editable }})
+    name: 'Conda (${{ matrix.os }}, Python ${{ matrix.python }}, editable: ${{ matrix.editable }})'
     runs-on: ${{ matrix.os }}-latest
 
     strategy:

From fba9bf7e12c5175fcd854baa712db41ca6aa63e5 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Thu, 23 Jan 2025 00:18:05 +0700
Subject: [PATCH 05/13] Hope this works

---
 .github/workflows/ci-meson.yml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 6d82586663d..6ab8ced8b34 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -81,7 +81,9 @@ jobs:
         shell: bash -l {0}
         run: |
           # We don't install sage_setup, so don't try to test it
-          rm -R ./src/sage_setup/
+          # If editable then deleting the directory will cause sage to detect rebuild, which will cause ninja to fail
+          # so we don't delete the directory in this case
+          ${{ matrix.editable && 'true' || 'rm -R ./src/sage_setup/' }}
           ./sage -t --all -p4
 
       - name: Upload log

From 4d5e89d6ab4e9b0600623a4f4861e5203f83d9a3 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Thu, 23 Jan 2025 07:53:14 +0700
Subject: [PATCH 06/13] Better name

---
 .github/workflows/ci-meson.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 6ab8ced8b34..56d01aaffbb 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -16,7 +16,7 @@ concurrency:
 
 jobs:
   test:
-    name: 'Conda (${{ matrix.os }}, Python ${{ matrix.python }}, editable: ${{ matrix.editable }})'
+    name: Conda (${{ matrix.os }}, Python ${{ matrix.python }}${{ matrix.editable && ', editable' || '' }})
     runs-on: ${{ matrix.os }}-latest
 
     strategy:

From c0e44723978a47703f89909589bd36c1b37b7579 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Sat, 1 Feb 2025 17:39:08 +0700
Subject: [PATCH 07/13] Avoid issues with artifact name collision

---
 .github/workflows/ci-meson.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 56d01aaffbb..930eca0f918 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -90,5 +90,5 @@ jobs:
         uses: actions/upload-artifact@v4.5.0
         if: failure()
         with:
-          name: ${{ runner.os }}-meson-${{ matrix.python }}-log
+          name: ${{ runner.os }}-meson-${{ matrix.python }}${{ matrix.editable && '-editable' || '' }}-log
           path: builddir/meson-logs/

From e366e2a7607971e4943e512898e23a5d769e464c Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Sat, 1 Feb 2025 18:01:49 +0700
Subject: [PATCH 08/13] Use import_module instead of find_spec

---
 src/sage/misc/dev_tools.py | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/src/sage/misc/dev_tools.py b/src/sage/misc/dev_tools.py
index b11b2078129..2a49310d66a 100644
--- a/src/sage/misc/dev_tools.py
+++ b/src/sage/misc/dev_tools.py
@@ -171,7 +171,7 @@ def load_submodules(module=None, exclude_pattern=None):
         load sage.geometry.polyhedron.ppl_lattice_polygon... succeeded
     """
     from .package_dir import walk_packages
-    import importlib.util
+    import importlib
 
     if module is None:
         import sage
@@ -195,12 +195,8 @@ def load_submodules(module=None, exclude_pattern=None):
         try:
             sys.stdout.write("load %s..." % module_name)
             sys.stdout.flush()
-            # see
-            # https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
-            spec = importer.find_spec(module_name)
-            module = importlib.util.module_from_spec(spec)
-            sys.modules[module_name] = module
-            spec.loader.exec_module(module)
+            module = importlib.import_module(module_name)
+            assert sys.modules[module_name] is module
             sys.stdout.write(" succeeded\n")
         except (ValueError, AttributeError, TypeError, ImportError):
             # we might get error because of cython code that has been

From 40c0b191526f9ff7246cb55f3ddfce970db0697a Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Tue, 11 Feb 2025 23:59:10 +0700
Subject: [PATCH 09/13] Fix more doctests in meson_editable install

---
 src/sage/doctest/external.py        |  4 +++
 src/sage/doctest/sources.py         | 10 +++++++
 src/sage/env.py                     |  4 +++
 src/sage/features/meson_editable.py | 46 +++++++++++++++++++++++++++++
 src/sage/misc/package_dir.py        | 36 ++++++++++++++++++++--
 5 files changed, 98 insertions(+), 2 deletions(-)
 create mode 100644 src/sage/features/meson_editable.py

diff --git a/src/sage/doctest/external.py b/src/sage/doctest/external.py
index 45b3987de05..2cc374f0763 100644
--- a/src/sage/doctest/external.py
+++ b/src/sage/doctest/external.py
@@ -366,6 +366,10 @@ def external_features():
     r"""
     Generate the features that are only to be tested if ``--optional=external`` is used.
 
+    .. SEEALSO::
+
+        :func:`sage.features.all.all_features`
+
     EXAMPLES::
 
         sage: from sage.doctest.external import external_features
diff --git a/src/sage/doctest/sources.py b/src/sage/doctest/sources.py
index 7589f62922b..01d24d67634 100644
--- a/src/sage/doctest/sources.py
+++ b/src/sage/doctest/sources.py
@@ -87,8 +87,18 @@ def get_basename(path):
         sage: import os
         sage: get_basename(sage.doctest.sources.__file__)
         'sage.doctest.sources'
+
+    ::
+
+        sage: # optional - !meson_editable
         sage: get_basename(os.path.join(sage.structure.__path__[0], 'element.pxd'))
         'sage.structure.element.pxd'
+
+    TESTS::
+
+        sage: # optional - meson_editable
+        sage: get_basename(os.path.join(os.path.dirname(sage.structure.__file__), 'element.pxd'))
+        'sage.structure.element.pxd'
     """
     if path is None:
         return None
diff --git a/src/sage/env.py b/src/sage/env.py
index 060eb2209a9..826c0343ac8 100644
--- a/src/sage/env.py
+++ b/src/sage/env.py
@@ -319,6 +319,10 @@ def sage_include_directories(use_sources=False):
         sage: dirs = sage.env.sage_include_directories(use_sources=True)
         sage: any(os.path.isfile(os.path.join(d, file)) for d in dirs)
         True
+
+    ::
+
+        sage: # optional - !meson_editable (no need, see :issue:`39275`)
         sage: dirs = sage.env.sage_include_directories(use_sources=False)
         sage: any(os.path.isfile(os.path.join(d, file)) for d in dirs)
         True
diff --git a/src/sage/features/meson_editable.py b/src/sage/features/meson_editable.py
new file mode 100644
index 00000000000..25969e562b4
--- /dev/null
+++ b/src/sage/features/meson_editable.py
@@ -0,0 +1,46 @@
+r"""
+Feature for testing if Meson editable install is used.
+"""
+
+import sys
+from . import Feature, FeatureTestResult
+
+
+class MesonEditable(Feature):
+    r"""
+    A :class:`~sage.features.Feature` describing if Meson editable install is used.
+
+    EXAMPLES::
+
+        sage: from sage.features.meson_editable import MesonEditable
+        sage: MesonEditable()
+        Feature('meson_editable')
+    """
+    def __init__(self):
+        r"""
+        TESTS::
+
+            sage: from sage.features.meson_editable import MesonEditable
+            sage: MesonEditable() is MesonEditable()
+            True
+        """
+        Feature.__init__(self, 'meson_editable')
+
+    def _is_present(self):
+        r"""
+        Test whether Meson editable install is used.
+
+        EXAMPLES::
+
+            sage: from sage.features.meson_editable import MesonEditable
+            sage: Internet()._is_present()  # random
+            FeatureTestResult('meson_editable', True)
+        """
+        import sage
+        import sys
+        result = type(sage.__loader__).__module__ == '_sagemath_editable_loader'
+        return FeatureTestResult(self, result)
+
+
+def all_features():
+    return [MesonEditable()]
diff --git a/src/sage/misc/package_dir.py b/src/sage/misc/package_dir.py
index 6b6ca12803f..b9742a6d1c2 100644
--- a/src/sage/misc/package_dir.py
+++ b/src/sage/misc/package_dir.py
@@ -261,6 +261,7 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
 
     :mod:`sage.cpython` is an ordinary package::
 
+        sage: # optional - !meson_editable
         sage: from sage.misc.package_dir import is_package_or_sage_namespace_package_dir
         sage: directory = sage.cpython.__path__[0]; directory
         '.../sage/cpython'
@@ -270,24 +271,48 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
     :mod:`sage.libs.mpfr` only has an ``__init__.pxd`` file, but we consider
     it a package directory for consistency with Cython::
 
+        sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.libs.__path__[0], 'mpfr'); directory
         '.../sage/libs/mpfr'
-        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
+        sage: is_package_or_sage_namespace_package_dir(directory)
         True
 
     :mod:`sage` is designated to become an implicit namespace package::
 
+        sage: # optional - !meson_editable
         sage: directory = sage.__path__[0]; directory
         '.../sage'
-        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
+        sage: is_package_or_sage_namespace_package_dir(directory)
         True
 
     Not a package::
 
+        sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.symbolic.__path__[0], 'ginac'); directory   # needs sage.symbolic
         '.../sage/symbolic/ginac'
         sage: is_package_or_sage_namespace_package_dir(directory)                       # needs sage.symbolic
         False
+
+    TESTS::
+
+        sage: # optional - meson_editable
+        sage: from sage.misc.package_dir import is_package_or_sage_namespace_package_dir
+        sage: directory = os.path.dirname(sage.cpython.__file__); directory
+        '.../sage/cpython'
+        sage: is_package_or_sage_namespace_package_dir(directory)
+        True
+
+        sage: # optional - meson_editable
+        sage: directory = os.path.join(os.path.dirname(sage.libs.__file__), 'mpfr'); directory
+        '.../sage/libs/mpfr'
+        sage: is_package_or_sage_namespace_package_dir(directory)
+        True
+
+        sage: # optional - meson_editable, sage.symbolic
+        sage: directory = os.path.join(os.path.dirname(sage.symbolic.__file__), 'ginac'); directory
+        '.../sage/symbolic/ginac'
+        sage: is_package_or_sage_namespace_package_dir(directory)
+        False
     """
     if os.path.exists(os.path.join(path, '__init__.py')):                # ordinary package
         return True
@@ -345,8 +370,15 @@ def walk_packages(path=None, prefix='', onerror=None):
 
     EXAMPLES::
 
+        sage: # optional - !meson_editable
         sage: sorted(sage.misc.package_dir.walk_packages(sage.misc.__path__))  # a namespace package
         [..., ModuleInfo(module_finder=FileFinder('.../sage/misc'), name='package_dir', ispkg=False), ...]
+
+    TESTS::
+
+        sage: # optional - meson_editable
+        sage: sorted(sage.misc.package_dir.walk_packages(sage.misc.__path__))
+        [..., ModuleInfo(module_finder=<...MesonpyPathFinder object...>, name='package_dir', ispkg=False), ...]
     """
     # Adapted from https://github.com/python/cpython/blob/3.11/Lib/pkgutil.py
 

From 88ecd7a9ca5c8a71fdda60e0735296a86417ac2c Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Wed, 12 Feb 2025 10:20:27 +0700
Subject: [PATCH 10/13] Revert "Fix more doctests in meson_editable install"

This reverts commit 40c0b191526f9ff7246cb55f3ddfce970db0697a.
---
 src/sage/doctest/external.py        |  4 ---
 src/sage/doctest/sources.py         | 10 -------
 src/sage/env.py                     |  4 ---
 src/sage/features/meson_editable.py | 46 -----------------------------
 src/sage/misc/package_dir.py        | 36 ++--------------------
 5 files changed, 2 insertions(+), 98 deletions(-)
 delete mode 100644 src/sage/features/meson_editable.py

diff --git a/src/sage/doctest/external.py b/src/sage/doctest/external.py
index 2cc374f0763..45b3987de05 100644
--- a/src/sage/doctest/external.py
+++ b/src/sage/doctest/external.py
@@ -366,10 +366,6 @@ def external_features():
     r"""
     Generate the features that are only to be tested if ``--optional=external`` is used.
 
-    .. SEEALSO::
-
-        :func:`sage.features.all.all_features`
-
     EXAMPLES::
 
         sage: from sage.doctest.external import external_features
diff --git a/src/sage/doctest/sources.py b/src/sage/doctest/sources.py
index 01d24d67634..7589f62922b 100644
--- a/src/sage/doctest/sources.py
+++ b/src/sage/doctest/sources.py
@@ -87,18 +87,8 @@ def get_basename(path):
         sage: import os
         sage: get_basename(sage.doctest.sources.__file__)
         'sage.doctest.sources'
-
-    ::
-
-        sage: # optional - !meson_editable
         sage: get_basename(os.path.join(sage.structure.__path__[0], 'element.pxd'))
         'sage.structure.element.pxd'
-
-    TESTS::
-
-        sage: # optional - meson_editable
-        sage: get_basename(os.path.join(os.path.dirname(sage.structure.__file__), 'element.pxd'))
-        'sage.structure.element.pxd'
     """
     if path is None:
         return None
diff --git a/src/sage/env.py b/src/sage/env.py
index 826c0343ac8..060eb2209a9 100644
--- a/src/sage/env.py
+++ b/src/sage/env.py
@@ -319,10 +319,6 @@ def sage_include_directories(use_sources=False):
         sage: dirs = sage.env.sage_include_directories(use_sources=True)
         sage: any(os.path.isfile(os.path.join(d, file)) for d in dirs)
         True
-
-    ::
-
-        sage: # optional - !meson_editable (no need, see :issue:`39275`)
         sage: dirs = sage.env.sage_include_directories(use_sources=False)
         sage: any(os.path.isfile(os.path.join(d, file)) for d in dirs)
         True
diff --git a/src/sage/features/meson_editable.py b/src/sage/features/meson_editable.py
deleted file mode 100644
index 25969e562b4..00000000000
--- a/src/sage/features/meson_editable.py
+++ /dev/null
@@ -1,46 +0,0 @@
-r"""
-Feature for testing if Meson editable install is used.
-"""
-
-import sys
-from . import Feature, FeatureTestResult
-
-
-class MesonEditable(Feature):
-    r"""
-    A :class:`~sage.features.Feature` describing if Meson editable install is used.
-
-    EXAMPLES::
-
-        sage: from sage.features.meson_editable import MesonEditable
-        sage: MesonEditable()
-        Feature('meson_editable')
-    """
-    def __init__(self):
-        r"""
-        TESTS::
-
-            sage: from sage.features.meson_editable import MesonEditable
-            sage: MesonEditable() is MesonEditable()
-            True
-        """
-        Feature.__init__(self, 'meson_editable')
-
-    def _is_present(self):
-        r"""
-        Test whether Meson editable install is used.
-
-        EXAMPLES::
-
-            sage: from sage.features.meson_editable import MesonEditable
-            sage: Internet()._is_present()  # random
-            FeatureTestResult('meson_editable', True)
-        """
-        import sage
-        import sys
-        result = type(sage.__loader__).__module__ == '_sagemath_editable_loader'
-        return FeatureTestResult(self, result)
-
-
-def all_features():
-    return [MesonEditable()]
diff --git a/src/sage/misc/package_dir.py b/src/sage/misc/package_dir.py
index b9742a6d1c2..6b6ca12803f 100644
--- a/src/sage/misc/package_dir.py
+++ b/src/sage/misc/package_dir.py
@@ -261,7 +261,6 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
 
     :mod:`sage.cpython` is an ordinary package::
 
-        sage: # optional - !meson_editable
         sage: from sage.misc.package_dir import is_package_or_sage_namespace_package_dir
         sage: directory = sage.cpython.__path__[0]; directory
         '.../sage/cpython'
@@ -271,48 +270,24 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
     :mod:`sage.libs.mpfr` only has an ``__init__.pxd`` file, but we consider
     it a package directory for consistency with Cython::
 
-        sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.libs.__path__[0], 'mpfr'); directory
         '.../sage/libs/mpfr'
-        sage: is_package_or_sage_namespace_package_dir(directory)
+        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
         True
 
     :mod:`sage` is designated to become an implicit namespace package::
 
-        sage: # optional - !meson_editable
         sage: directory = sage.__path__[0]; directory
         '.../sage'
-        sage: is_package_or_sage_namespace_package_dir(directory)
+        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
         True
 
     Not a package::
 
-        sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.symbolic.__path__[0], 'ginac'); directory   # needs sage.symbolic
         '.../sage/symbolic/ginac'
         sage: is_package_or_sage_namespace_package_dir(directory)                       # needs sage.symbolic
         False
-
-    TESTS::
-
-        sage: # optional - meson_editable
-        sage: from sage.misc.package_dir import is_package_or_sage_namespace_package_dir
-        sage: directory = os.path.dirname(sage.cpython.__file__); directory
-        '.../sage/cpython'
-        sage: is_package_or_sage_namespace_package_dir(directory)
-        True
-
-        sage: # optional - meson_editable
-        sage: directory = os.path.join(os.path.dirname(sage.libs.__file__), 'mpfr'); directory
-        '.../sage/libs/mpfr'
-        sage: is_package_or_sage_namespace_package_dir(directory)
-        True
-
-        sage: # optional - meson_editable, sage.symbolic
-        sage: directory = os.path.join(os.path.dirname(sage.symbolic.__file__), 'ginac'); directory
-        '.../sage/symbolic/ginac'
-        sage: is_package_or_sage_namespace_package_dir(directory)
-        False
     """
     if os.path.exists(os.path.join(path, '__init__.py')):                # ordinary package
         return True
@@ -370,15 +345,8 @@ def walk_packages(path=None, prefix='', onerror=None):
 
     EXAMPLES::
 
-        sage: # optional - !meson_editable
         sage: sorted(sage.misc.package_dir.walk_packages(sage.misc.__path__))  # a namespace package
         [..., ModuleInfo(module_finder=FileFinder('.../sage/misc'), name='package_dir', ispkg=False), ...]
-
-    TESTS::
-
-        sage: # optional - meson_editable
-        sage: sorted(sage.misc.package_dir.walk_packages(sage.misc.__path__))
-        [..., ModuleInfo(module_finder=<...MesonpyPathFinder object...>, name='package_dir', ispkg=False), ...]
     """
     # Adapted from https://github.com/python/cpython/blob/3.11/Lib/pkgutil.py
 

From 85fb2e6c9ae52ece34054e03324af6fb3d6df7d6 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Tue, 11 Feb 2025 23:59:10 +0700
Subject: [PATCH 11/13] Fix more doctests in meson_editable install

---
 src/sage/doctest/external.py        |  4 +++
 src/sage/doctest/sources.py         | 10 +++++++
 src/sage/env.py                     |  4 +++
 src/sage/features/meson_editable.py | 45 +++++++++++++++++++++++++++++
 src/sage/misc/package_dir.py        | 36 +++++++++++++++++++++--
 5 files changed, 97 insertions(+), 2 deletions(-)
 create mode 100644 src/sage/features/meson_editable.py

diff --git a/src/sage/doctest/external.py b/src/sage/doctest/external.py
index 45b3987de05..2cc374f0763 100644
--- a/src/sage/doctest/external.py
+++ b/src/sage/doctest/external.py
@@ -366,6 +366,10 @@ def external_features():
     r"""
     Generate the features that are only to be tested if ``--optional=external`` is used.
 
+    .. SEEALSO::
+
+        :func:`sage.features.all.all_features`
+
     EXAMPLES::
 
         sage: from sage.doctest.external import external_features
diff --git a/src/sage/doctest/sources.py b/src/sage/doctest/sources.py
index 7589f62922b..01d24d67634 100644
--- a/src/sage/doctest/sources.py
+++ b/src/sage/doctest/sources.py
@@ -87,8 +87,18 @@ def get_basename(path):
         sage: import os
         sage: get_basename(sage.doctest.sources.__file__)
         'sage.doctest.sources'
+
+    ::
+
+        sage: # optional - !meson_editable
         sage: get_basename(os.path.join(sage.structure.__path__[0], 'element.pxd'))
         'sage.structure.element.pxd'
+
+    TESTS::
+
+        sage: # optional - meson_editable
+        sage: get_basename(os.path.join(os.path.dirname(sage.structure.__file__), 'element.pxd'))
+        'sage.structure.element.pxd'
     """
     if path is None:
         return None
diff --git a/src/sage/env.py b/src/sage/env.py
index 060eb2209a9..826c0343ac8 100644
--- a/src/sage/env.py
+++ b/src/sage/env.py
@@ -319,6 +319,10 @@ def sage_include_directories(use_sources=False):
         sage: dirs = sage.env.sage_include_directories(use_sources=True)
         sage: any(os.path.isfile(os.path.join(d, file)) for d in dirs)
         True
+
+    ::
+
+        sage: # optional - !meson_editable (no need, see :issue:`39275`)
         sage: dirs = sage.env.sage_include_directories(use_sources=False)
         sage: any(os.path.isfile(os.path.join(d, file)) for d in dirs)
         True
diff --git a/src/sage/features/meson_editable.py b/src/sage/features/meson_editable.py
new file mode 100644
index 00000000000..a110648b873
--- /dev/null
+++ b/src/sage/features/meson_editable.py
@@ -0,0 +1,45 @@
+r"""
+Feature for testing if Meson editable install is used.
+"""
+
+import sys
+from . import Feature, FeatureTestResult
+
+
+class MesonEditable(Feature):
+    r"""
+    A :class:`~sage.features.Feature` describing if Meson editable install is used.
+
+    EXAMPLES::
+
+        sage: from sage.features.meson_editable import MesonEditable
+        sage: MesonEditable()
+        Feature('meson_editable')
+    """
+    def __init__(self):
+        r"""
+        TESTS::
+
+            sage: from sage.features.meson_editable import MesonEditable
+            sage: MesonEditable() is MesonEditable()
+            True
+        """
+        Feature.__init__(self, 'meson_editable')
+
+    def _is_present(self):
+        r"""
+        Test whether Meson editable install is used.
+
+        EXAMPLES::
+
+            sage: from sage.features.meson_editable import MesonEditable
+            sage: MesonEditable()._is_present()  # random
+            FeatureTestResult('meson_editable', True)
+        """
+        import sage
+        result = type(sage.__loader__).__module__ == '_sagemath_editable_loader'
+        return FeatureTestResult(self, result)
+
+
+def all_features():
+    return [MesonEditable()]
diff --git a/src/sage/misc/package_dir.py b/src/sage/misc/package_dir.py
index 6b6ca12803f..b9742a6d1c2 100644
--- a/src/sage/misc/package_dir.py
+++ b/src/sage/misc/package_dir.py
@@ -261,6 +261,7 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
 
     :mod:`sage.cpython` is an ordinary package::
 
+        sage: # optional - !meson_editable
         sage: from sage.misc.package_dir import is_package_or_sage_namespace_package_dir
         sage: directory = sage.cpython.__path__[0]; directory
         '.../sage/cpython'
@@ -270,24 +271,48 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
     :mod:`sage.libs.mpfr` only has an ``__init__.pxd`` file, but we consider
     it a package directory for consistency with Cython::
 
+        sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.libs.__path__[0], 'mpfr'); directory
         '.../sage/libs/mpfr'
-        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
+        sage: is_package_or_sage_namespace_package_dir(directory)
         True
 
     :mod:`sage` is designated to become an implicit namespace package::
 
+        sage: # optional - !meson_editable
         sage: directory = sage.__path__[0]; directory
         '.../sage'
-        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
+        sage: is_package_or_sage_namespace_package_dir(directory)
         True
 
     Not a package::
 
+        sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.symbolic.__path__[0], 'ginac'); directory   # needs sage.symbolic
         '.../sage/symbolic/ginac'
         sage: is_package_or_sage_namespace_package_dir(directory)                       # needs sage.symbolic
         False
+
+    TESTS::
+
+        sage: # optional - meson_editable
+        sage: from sage.misc.package_dir import is_package_or_sage_namespace_package_dir
+        sage: directory = os.path.dirname(sage.cpython.__file__); directory
+        '.../sage/cpython'
+        sage: is_package_or_sage_namespace_package_dir(directory)
+        True
+
+        sage: # optional - meson_editable
+        sage: directory = os.path.join(os.path.dirname(sage.libs.__file__), 'mpfr'); directory
+        '.../sage/libs/mpfr'
+        sage: is_package_or_sage_namespace_package_dir(directory)
+        True
+
+        sage: # optional - meson_editable, sage.symbolic
+        sage: directory = os.path.join(os.path.dirname(sage.symbolic.__file__), 'ginac'); directory
+        '.../sage/symbolic/ginac'
+        sage: is_package_or_sage_namespace_package_dir(directory)
+        False
     """
     if os.path.exists(os.path.join(path, '__init__.py')):                # ordinary package
         return True
@@ -345,8 +370,15 @@ def walk_packages(path=None, prefix='', onerror=None):
 
     EXAMPLES::
 
+        sage: # optional - !meson_editable
         sage: sorted(sage.misc.package_dir.walk_packages(sage.misc.__path__))  # a namespace package
         [..., ModuleInfo(module_finder=FileFinder('.../sage/misc'), name='package_dir', ispkg=False), ...]
+
+    TESTS::
+
+        sage: # optional - meson_editable
+        sage: sorted(sage.misc.package_dir.walk_packages(sage.misc.__path__))
+        [..., ModuleInfo(module_finder=<...MesonpyPathFinder object...>, name='package_dir', ispkg=False), ...]
     """
     # Adapted from https://github.com/python/cpython/blob/3.11/Lib/pkgutil.py
 

From b1606b58cb19ad2fcee596ee02f7cf0501828937 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Wed, 12 Feb 2025 11:11:10 +0700
Subject: [PATCH 12/13] Workaround for test-new failure

---
 src/sage/misc/package_dir.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sage/misc/package_dir.py b/src/sage/misc/package_dir.py
index 6358bc1d265..16364fb1483 100644
--- a/src/sage/misc/package_dir.py
+++ b/src/sage/misc/package_dir.py
@@ -274,7 +274,7 @@ def is_package_or_sage_namespace_package_dir(path, *, distribution_filter=None):
         sage: # optional - !meson_editable
         sage: directory = os.path.join(sage.libs.__path__[0], 'mpfr'); directory
         '.../sage/libs/mpfr'
-        sage: is_package_or_sage_namespace_package_dir(directory)
+        sage: is_package_or_sage_namespace_package_dir(directory)       # known bug (seen in build.yml)
         True
 
     :mod:`sage` is designated to become an implicit namespace package::

From b14e2e92cdc1c3c437c2359a4b3e434dd6c86486 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Mon, 3 Mar 2025 22:27:45 +0700
Subject: [PATCH 13/13] Only run 2/4 combinations in pull_request

---
 .github/workflows/ci-meson.yml | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/.github/workflows/ci-meson.yml b/.github/workflows/ci-meson.yml
index 91cf277296c..0b3f6401bc2 100644
--- a/.github/workflows/ci-meson.yml
+++ b/.github/workflows/ci-meson.yml
@@ -25,6 +25,19 @@ jobs:
         os: [ubuntu]
         python: ['3.11', '3.12']
         editable: [false, true]
+        is-pull-request:
+          - ${{ github.event_name == 'pull_request' }}
+          # trick from https://github.com/orgs/community/discussions/26253#discussioncomment-6745038
+          # in PR, only run the combinations listed below; otherwise, run all combinations
+        exclude:
+          - is-pull-request: true
+        include:
+          - os: ubuntu
+            python: 3.11
+            editable: false
+          - os: ubuntu
+            python: 3.12
+            editable: true
 
     steps:
       - uses: actions/checkout@v4