Add a custom hook for dev_path changes (#46529)

* Add a custom hook for dev_path changes

Co-authored-by: Greg Becker <becker33@llnl.gov>

lib/spack/docs/environments.rst

@@ -414,7 +414,13 @@ default, it will also clone the package to a subdirectory in the
 environment. This package will have a special variant ``dev_path``
 set, and Spack will ensure the package and its dependents are rebuilt
 any time the environment is installed if the package's local source
-code has been modified. Spack ensures that all instances of a
+code has been modified. Spack's native implementation to check for modifications
+is to check if ``mtime`` is newer than the installation.
+A custom check can be created by overriding the ``detect_dev_src_change`` method 
+in your package class. This is particularly useful for projects using custom spack repo's 
+to drive development and want to optimize performance. 
+
+Spack ensures that all instances of a
 developed package in the environment are concretized to match the
 version (and other constraints) passed as the spec argument to the
 ``spack develop`` command.

lib/spack/spack/environment/environment.py

@@ -546,8 +546,7 @@ def _is_dev_spec_and_has_changed(spec):
     last installation"""
     # First check if this is a dev build and in the process already try to get
     # the dev_path
-    dev_path_var = spec.variants.get("dev_path", None)
-    if not dev_path_var:
+    if not spec.variants.get("dev_path", None):
         return False
 
     # Now we can check whether the code changed since the last installation
@@ -555,9 +554,10 @@ def _is_dev_spec_and_has_changed(spec):
         # Not installed -> nothing to compare against
         return False
 
-    _, record = spack.store.STORE.db.query_by_spec_hash(spec.dag_hash())
-    mtime = fs.last_modification_time_recursive(dev_path_var.value)
-    return mtime > record.installation_time
+    # hook so packages can use to write their own method for checking the dev_path
+    # use package so attributes about concretization such as variant state can be
+    # utilized
+    return spec.package.detect_dev_src_change()
 
 
 def _error_on_nonempty_view_dir(new_root):

lib/spack/spack/package_base.py

@@ -1101,6 +1101,15 @@ def update_external_dependencies(self, extendee_spec=None):
         """
         pass
 
+    def detect_dev_src_change(self):
+        """
+        Method for checking for source code changes to trigger rebuild/reinstall
+        """
+        dev_path_var = self.spec.variants.get("dev_path", None)
+        _, record = spack.store.STORE.db.query_by_spec_hash(self.spec.dag_hash())
+        mtime = fsys.last_modification_time_recursive(dev_path_var.value)
+        return mtime > record.installation_time
+
     def all_urls_for_version(self, version: StandardVersion) -> List[str]:
         """Return all URLs derived from version_urls(), url, urls, and
         list_url (if it contains a version) in a package in that order.