spec.py: make parser select from environment (#30276)

The parser is already committing a crime of querying the database for
specs when it encounters a `/hash`. It's helpful, but unfortunately not
helpful when trying to install a specific spec in an environment by
hash. Therefore, consider the environment first, then the database.

This allows the following:

```console
$ spack -e . concretize
==> Starting concretization
==> Environment concretized in 0.27 seconds.
==> Concretized diffutils
 -   7vangk4  diffutils@3.8%gcc@10.3.0 arch=linux-ubuntu20.04-zen2
 -   hyb7ehx      ^libiconv@1.16%gcc@10.3.0 libs=shared,static arch=linux-ubuntu20.04-zen2

$ spack -e . install /hyb7ehx
==> Installing libiconv-1.16-hyb7ehxxyqqp2hiw56bzm5ampkw6cxws
...
==> libiconv: Successfully installed libiconv-1.16-hyb7ehxxyqqp2hiw56bzm5ampkw6cxws
  Fetch: 0.01s.  Build: 17.54s.  Total: 17.55s.
[+] /tmp/tmp.VpvYApofVm/store/linux-ubuntu20.04-zen2/gcc-10.3.0/libiconv-1.16-hyb7ehxxyqqp2hiw56bzm5ampkw6cxws
```

lib/spack/spack/environment/environment.py

@@ -1659,6 +1659,15 @@ def concretized_specs(self):
         for s, h in zip(self.concretized_user_specs, self.concretized_order):
             yield (s, self.specs_by_hash[h])
 
+    def get_by_hash(self, dag_hash):
+        matches = {}
+        for _, root in self.concretized_specs():
+            for spec in root.traverse(root=True):
+                dep_hash = spec.dag_hash()
+                if dep_hash.startswith(dag_hash):
+                    matches[dep_hash] = spec
+        return list(matches.values())
+
     def matching_spec(self, spec):
         """
         Given a spec (likely not concretized), find a matching concretized

lib/spack/spack/spec.py

@@ -5167,9 +5167,14 @@ def parse_compiler(self, text):
         return self.compiler()
 
     def spec_by_hash(self):
+        # TODO: Remove parser dependency on active environment and database.
+        import spack.environment
         self.expect(ID)
-
         dag_hash = self.token.value
+        matches = []
+        if spack.environment.active_environment():
+            matches = spack.environment.active_environment().get_by_hash(dag_hash)
+        if not matches:
             matches = spack.store.db.get_by_hash(dag_hash)
         if not matches:
             raise NoSuchHashError(dag_hash)

lib/spack/spack/test/cmd/env.py

@@ -2843,3 +2843,16 @@ def test_environment_view_target_already_exists(
     # Make sure the dir was left untouched.
     assert not os.path.lexists(view)
     assert os.listdir(real_view) == ['file']
+
+
+def test_environment_query_spec_by_hash(mock_stage, mock_fetch, install_mockery):
+    env('create', 'test')
+    with ev.read('test'):
+        add('libdwarf')
+        concretize()
+    with ev.read('test') as e:
+        spec = e.matching_spec('libelf')
+        install('/{0}'.format(spec.dag_hash()))
+    with ev.read('test') as e:
+        assert not e.matching_spec('libdwarf').installed
+        assert e.matching_spec('libelf').installed