Make --namespace-packages the default

mypy/build.py

@@ -1325,8 +1325,10 @@ def validate_meta(meta: Optional[CacheMeta], id: str, path: Optional[str],
         st = manager.get_stat(path)
     except OSError:
         return None
-    if not (stat.S_ISREG(st.st_mode) or stat.S_ISDIR(st.st_mode)):
-        manager.log('Metadata abandoned for {}: file {} does not exist'.format(id, path))
+    if not stat.S_ISDIR(st.st_mode) and not stat.S_ISREG(st.st_mode):
+        manager.log(
+            'Metadata abandoned for {}: file or directory {} does not exist'.format(id, path)
+        )
         return None
 
     manager.add_stats(validate_stat_time=time.time() - t0)

mypy/main.py

@@ -516,7 +516,7 @@ def add_invertible_flag(flag: str,
         title='Import discovery',
         description="Configure how imports are discovered and followed.")
     add_invertible_flag(
-        '--namespace-packages', default=False,
+        '--no-namespace-packages', dest="namespace_packages", default=True,
         help="Support namespace packages (PEP 420, __init__.py-less)",
         group=imports_group)
     imports_group.add_argument(

mypy/options.py

@@ -92,7 +92,7 @@ def __init__(self) -> None:
         # This allows definitions of packages without __init__.py and allows packages to span
         # multiple directories. This flag affects both import discovery and the association of
         # input files/modules/packages to the relevant file and fully qualified module name.
-        self.namespace_packages = False
+        self.namespace_packages = True
         # Use current directory and MYPYPATH to determine fully qualified module names of files
         # passed by automatically considering their subdirectories as packages. This is only
         # relevant if namespace packages are enabled, since otherwise examining __init__.py's is

test-data/unit/check-modules.test

@@ -2655,12 +2655,13 @@ from foo.bar import x
 x = 0
 
 [case testClassicNotPackage]
+# flags: --no-namespace-packages
 from foo.bar import x
 [file foo/bar.py]
 x = 0
 [out]
-main:1: error: Cannot find implementation or library stub for module named "foo.bar"
-main:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+main:2: error: Cannot find implementation or library stub for module named "foo.bar"
+main:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
 
 [case testNamespacePackage]
 # flags: --namespace-packages

test-data/unit/fine-grained-modules.test

@@ -845,7 +845,7 @@ main:2: error: Argument 1 to "f" has incompatible type "int"; expected "str"
 ==
 main:1: error: Cannot find implementation or library stub for module named "p.a"
 main:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
-main:1: error: Cannot find implementation or library stub for module named "p"
+main:2: error: "object" has no attribute "a"
 
 [case testDeletePackage2]
 import p

test-data/unit/semanal-errors.test

@@ -316,15 +316,16 @@ x = y
 tmp/k.py:2: error: Name "y" is not defined
 
 [case testPackageWithoutInitFile]
+# flags: --no-namespace-packages
 import typing
 import m.n
 m.n.x
 [file m/n.py]
 x = 1
 [out]
-main:2: error: Cannot find implementation or library stub for module named "m.n"
-main:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
-main:2: error: Cannot find implementation or library stub for module named "m"
+main:3: error: Cannot find implementation or library stub for module named "m.n"
+main:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+main:3: error: Cannot find implementation or library stub for module named "m"
 
 [case testBreakOutsideLoop]
 break