Don't inject import statements in package recipes

Remove a hack done by RepoLoader, which was injecting an extra
```
from spack.package import *
```
at the beginning of each package.py

lib/spack/spack/repo.py

@@ -81,43 +81,6 @@ def namespace_from_fullname(fullname):
     return namespace
 
 
-class _PrependFileLoader(importlib.machinery.SourceFileLoader):
-    def __init__(self, fullname, path, prepend=None):
-        super(_PrependFileLoader, self).__init__(fullname, path)
-        self.prepend = prepend
-
-    def path_stats(self, path):
-        stats = super(_PrependFileLoader, self).path_stats(path)
-        if self.prepend:
-            stats["size"] += len(self.prepend) + 1
-        return stats
-
-    def get_data(self, path):
-        data = super(_PrependFileLoader, self).get_data(path)
-        if path != self.path or self.prepend is None:
-            return data
-        else:
-            return self.prepend.encode() + b"\n" + data
-
-
-class RepoLoader(_PrependFileLoader):
-    """Loads a Python module associated with a package in specific repository"""
-
-    #: Code in ``_package_prepend`` is prepended to imported packages.
-    #:
-    #: Spack packages are expected to call `from spack.package import *`
-    #: themselves, but we are allowing a deprecation period before breaking
-    #: external repos that don't do this yet.
-    _package_prepend = "from spack.package import *"
-
-    def __init__(self, fullname, repo, package_name):
-        self.repo = repo
-        self.package_name = package_name
-        self.package_py = repo.filename_for_package_name(package_name)
-        self.fullname = fullname
-        super().__init__(self.fullname, self.package_py, prepend=self._package_prepend)
-
-
 class SpackNamespaceLoader:
     def create_module(self, spec):
         return SpackNamespace(spec.name)
@@ -187,7 +150,8 @@ def compute_loader(self, fullname):
                 # With 2 nested conditionals we can call "repo.real_name" only once
                 package_name = repo.real_name(module_name)
                 if package_name:
-                    return RepoLoader(fullname, repo, package_name)
+                    module_path = repo.filename_for_package_name(package_name)
+                    return importlib.machinery.SourceFileLoader(fullname, module_path)
 
             # We are importing a full namespace like 'spack.pkg.builtin'
             if fullname == repo.full_namespace:

lib/spack/spack/test/cmd/diff.py

@@ -20,6 +20,8 @@
 _p1 = (
     "p1",
     """\
+from spack.package import *
+
 class P1(Package):
     version("1.0")
 
@@ -35,6 +37,8 @@ class P1(Package):
 _p2 = (
     "p2",
     """\
+from spack.package import *
+
 class P2(Package):
     version("1.0")
 
@@ -48,6 +52,8 @@ class P2(Package):
 _p3 = (
     "p3",
     """\
+from spack.package import *
+
 class P3(Package):
     version("1.0")
 
@@ -58,6 +64,8 @@ class P3(Package):
 _i1 = (
     "i1",
     """\
+from spack.package import *
+
 class I1(Package):
     version("1.0")
 
@@ -73,6 +81,8 @@ class I1(Package):
 _i2 = (
     "i2",
     """\
+from spack.package import *
+
 class I2(Package):
     version("1.0")
 
@@ -89,6 +99,8 @@ class I2(Package):
 _p4 = (
     "p4",
     """\
+from spack.package import *
+
 class P4(Package):
     version("1.0")
 

lib/spack/spack/test/cmd/find.py

@@ -462,6 +462,8 @@ def test_environment_with_version_range_in_compiler_doesnt_fail(tmp_path):
 _pkga = (
     "a0",
     """\
+from spack.package import *
+
 class A0(Package):
     version("1.2")
     version("1.1")
@@ -475,6 +477,8 @@ class A0(Package):
 _pkgb = (
     "b0",
     """\
+from spack.package import *
+
 class B0(Package):
     version("1.2")
     version("1.1")
@@ -485,6 +489,8 @@ class B0(Package):
 _pkgc = (
     "c0",
     """\
+from spack.package import *
+
 class C0(Package):
     version("1.2")
     version("1.1")
@@ -497,6 +503,8 @@ class C0(Package):
 _pkgd = (
     "d0",
     """\
+from spack.package import *
+
 class D0(Package):
     version("1.2")
     version("1.1")
@@ -510,6 +518,8 @@ class D0(Package):
 _pkge = (
     "e0",
     """\
+from spack.package import *
+
 class E0(Package):
     tags = ["tag1", "tag2"]
 

lib/spack/spack/test/concretization/core.py

@@ -188,6 +188,8 @@ def repo_with_changing_recipe(tmp_path_factory, mutable_mock_repo):
 
     packages_dir = repo_dir / "packages"
     root_pkg_str = """
+from spack.package import *
+
 class Root(Package):
     homepage = "http://www.example.com"
     url      = "http://www.example.com/root-1.0.tar.gz"
@@ -202,6 +204,8 @@ class Root(Package):
     package_py.write_text(root_pkg_str)
 
     changing_template = """
+from spack.package import *
+
 class Changing(Package):
     homepage = "http://www.example.com"
     url      = "http://www.example.com/changing-1.0.tar.gz"

lib/spack/spack/test/directives.py

@@ -148,6 +148,8 @@ def test_version_type_validation():
 _pkgx = (
     "x",
     """\
+from spack.package import *
+
 class X(Package):
     version("1.3")
     version("1.2")
@@ -166,6 +168,8 @@ class X(Package):
 _pkgy = (
     "y",
     """\
+from spack.package import *
+
 class Y(Package):
     version("2.1")
     version("2.0")

share/spack/templates/mock-repository/package.pyt

@@ -1,3 +1,5 @@
+from spack.package import *
+
 class {{ cls_name }}(Package):
     homepage = "http://www.example.com"
     url = "http://www.example.com/root-1.0.tar.gz"