Rename lz_submodule to lz_dotted_as and trim the comments

The flag means "bind the whole dotted name, not the root", which the old
name did not say, and import.c already has unrelated lazy_pending_submodules
machinery to be confused with.

Author: brittanyrey

Include/internal/pycore_lazyimportobject.h

@@ -22,15 +22,14 @@ typedef struct {
     // Frame information for the original import location.
     PyCodeObject *lz_code;     // Code object where the lazy import was created.
     int lz_instr_offset;       // Instruction offset where the lazy import was created.
-    int lz_submodule;          // True for `import a.b as c`, which binds `a.b`
-                               // where `import a.b` binds `a`.
+    int lz_dotted_as;          // `import a.b as c`, which binds `a.b` not `a`.
 } PyLazyImportObject;
 
 
 PyAPI_FUNC(PyObject *) _PyLazyImport_GetName(PyObject *lazy_import);
 PyAPI_FUNC(PyObject *) _PyLazyImport_New(
     struct _PyInterpreterFrame *frame, PyObject *import_func, PyObject *from,
-    PyObject *attr, int submodule);
+    PyObject *attr, int dotted_as);
 
 #ifdef __cplusplus
 }

Lib/test/test_lazy_import/__init__.py

@@ -725,8 +725,7 @@ def test_non_package_lazily_imported(self):
 
     def test_non_package_lazily_imported_as(self):
         """A dotted lazy import as raises when the name is not a module."""
-        # gh-157757: the eager statement raises ModuleNotFoundError, so the
-        # lazy one raises it at first use rather than binding math.pi.
+        # gh-157757: the eager statement raises, so the lazy one raises too.
         code = textwrap.dedent("""
             lazy import math.pi as pi
 
@@ -2219,9 +2218,8 @@ def test_import_after_variable_wins(self):
 
     def test_lazy_import_as_wins_over_variable(self):
         """A dotted lazy import as imports the submodule the variable hides."""
-        # gh-157757: the eager statement imports pkg.b, which rebinds pkg.b to
-        # the module, so the lazy one must import it too rather than read the
-        # variable off pkg.
+        # gh-157757: importing pkg.b rebinds pkg.b from the variable to the
+        # module, eagerly and lazily alike.
         code = textwrap.dedent("""
             import sys
             import test.test_lazy_import.data.pkg as pkg

Objects/lazyimportobject.c

@@ -12,7 +12,7 @@
 
 PyObject *
 _PyLazyImport_New(_PyInterpreterFrame *frame, PyObject *builtins,
-                  PyObject *name, PyObject *fromlist, int submodule)
+                  PyObject *name, PyObject *fromlist, int dotted_as)
 {
     PyLazyImportObject *m;
     if (!name || !PyUnicode_Check(name)) {
@@ -34,7 +34,7 @@ _PyLazyImport_New(_PyInterpreterFrame *frame, PyObject *builtins,
     m->lz_builtins = Py_XNewRef(builtins);
     m->lz_from = Py_NewRef(name);
     m->lz_attr = Py_XNewRef(fromlist);
-    m->lz_submodule = submodule;
+    m->lz_dotted_as = dotted_as;
 
     // Capture frame information for the original import location.
     m->lz_code = NULL;

Python/ceval.c

@@ -3335,9 +3335,9 @@ _PyEval_LazyImportFrom(PyThreadState *tstate, _PyInterpreterFrame *frame, PyObje
     PyLazyImportObject *d = (PyLazyImportObject *)v;
 
     if (d->lz_attr == NULL) {
-        // `import a.b as x` binds `a.b`, not an attribute of `a` (gh-157757).
-        if (d->lz_submodule) {
-            return Py_NewRef(v);  // a later component of the same name
+        // `import a.b as x` binds the module `a.b`, not an attribute of `a`.
+        if (d->lz_dotted_as) {
+            return Py_NewRef(v);
         }
         return _PyLazyImport_New(frame, d->lz_builtins, d->lz_from, NULL, 1);
     }
@@ -3362,7 +3362,7 @@ _PyEval_LazyImportFrom(PyThreadState *tstate, _PyInterpreterFrame *frame, PyObje
         Py_DECREF(mod);
     }
 
-    assert(!PyUnicode_Check(d->lz_attr));  // a fromlist, not a taken name
+    assert(!PyUnicode_Check(d->lz_attr));  // a fromlist
     return _PyLazyImport_New(frame, d->lz_builtins, d->lz_from, name, 0);
 }
 

Python/import.c

@@ -3898,8 +3898,7 @@ _PyImport_ResolveName(PyThreadState *tstate, PyObject *name,
   return resolve_name(tstate, name, globals, level);
 }
 
-// Repeat IMPORT_FROM over the components of `name` after the first, taking
-// `a.b.c` off the `a` that importing "a.b.c" returns.
+// Take `a.b.c` off the `a` that importing "a.b.c" returns, as IMPORT_FROM does.
 static PyObject *
 import_from_dotted_name(PyThreadState *tstate, PyObject *mod, PyObject *name)
 {
@@ -4010,7 +4009,7 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
         goto error;
     }
 
-    if (lz->lz_submodule) {
+    if (lz->lz_dotted_as) {
         PyObject *top = obj;
         obj = import_from_dotted_name(tstate, top, lz->lz_from);
         Py_DECREF(top);