directory_layout: remove outdated checks for old DAG hash

We previously had checks in `directory_layout` to check for build-dependency
conflicts when we weren't storing build dependencies.  We don't need
those anymore; we can just rely on the DAG hash now that it includes everything
we know about each spec.

- [x] Remove vestigial code for checking installed spec against concrete spec
      in `ensure_installed()`
- [x] Remove `SpecHashCollisionError` -- if specs have the same hash now, they're
      the same as far as `DirectoryLayout` should be concerned.
- [x] Convert spec comparison to `dag_hash()` comparison when adding extensions.

2 files changed, 6 insertions, 34 deletions

diff --git a/lib/spack/spack/directory_layout.py b/lib/spack/spack/directory_layout.py
index 56ba01c7b4..3ccec788d8 100644
--- a/lib/spack/spack/directory_layout.py
+++ b/lib/spack/spack/directory_layout.py
@@ -238,10 +238,10 @@ class DirectoryLayout(object):
 
     def ensure_installed(self, spec):
         """
-        Throws DirectoryLayoutError if:
+        Throws InconsistentInstallDirectoryError if:
         1. spec prefix does not exist
-        2. spec prefix does not contain a spec file
-        3. the spec file does not correspond to the spec
+        2. spec prefix does not contain a spec file, or
+        3. We read a spec with the wrong DAG hash out of an existing install directory.
         """
         _check_concrete(spec)
         path = self.path_for_spec(spec)
@@ -257,25 +257,7 @@ class DirectoryLayout(object):
                 "  " + path)
 
         installed_spec = self.read_spec(spec_file_path)
-        if installed_spec == spec:
-            return
-
-        # DAG hashes currently do not include build dependencies.
-        #
-        # TODO: remove this when we do better concretization and don't
-        # ignore build-only deps in hashes.
-        elif (installed_spec.copy(deps=('link', 'run')) ==
-              spec.copy(deps=('link', 'run'))):
-            # The directory layout prefix is based on the dag hash, so among
-            # specs with differing full-hash but matching dag-hash, only one
-            # may be installed. This means for example that for two instances
-            # that differ only in CMake version used to build, only one will
-            # be installed.
-            return
-
-        if spec.dag_hash() == installed_spec.dag_hash():
-            raise SpecHashCollisionError(spec, installed_spec)
-        else:
+        if installed_spec.dag_hash() != spec.dag_hash():
             raise InconsistentInstallDirectoryError(
                 'Spec file in %s does not match hash!' % spec_file_path)
 
@@ -463,8 +445,8 @@ class YamlViewExtensionsLayout(ExtensionsLayout):
     def check_extension_conflict(self, spec, ext_spec):
         exts = self._extension_map(spec)
         if ext_spec.name in exts:
-            installed_spec = exts[ext_spec.name].copy(deps=('link', 'run'))
-            if ext_spec.copy(deps=('link', 'run')) == installed_spec:
+            installed_spec = exts[ext_spec.name]
+            if ext_spec.dag_hash() == installed_spec.dag_hash():
                 raise ExtensionAlreadyInstalledError(spec, ext_spec)
             else:
                 raise ExtensionConflictError(spec, ext_spec, installed_spec)
@@ -584,15 +566,6 @@ class DirectoryLayoutError(SpackError):
         super(DirectoryLayoutError, self).__init__(message, long_msg)
 
 
-class SpecHashCollisionError(DirectoryLayoutError):
-    """Raised when there is a hash collision in an install layout."""
-
-    def __init__(self, installed_spec, new_spec):
-        super(SpecHashCollisionError, self).__init__(
-            'Specs %s and %s have the same SHA-1 prefix!'
-            % (installed_spec, new_spec))
-
-
 class RemoveFailedError(DirectoryLayoutError):
     """Raised when a DirectoryLayout cannot remove an install prefix."""
 
diff --git a/lib/spack/spack/environment/environment.py b/lib/spack/spack/environment/environment.py
index 6ed4297fca..8c71deb561 100644
--- a/lib/spack/spack/environment/environment.py
+++ b/lib/spack/spack/environment/environment.py
@@ -1828,7 +1828,6 @@ class Environment(object):
             spec = Spec.from_node_dict(node_dict)
             if not spec._hash:
                 # in v1 lockfiles, the hash only occurs as a key
-                print("HERE")
                 spec._hash = lockfile_key
             specs_by_hash[lockfile_key] = spec