Allow configurable stage names (#36509)

Add `config:stage_name` which is a Spec format string that can
customize the names of stages created by Spack. This was primarily
created to allow generating shorter stage names on Windows (along
with `config:build_stage`, this can be used to create stages with
short absolute paths).

By default, this is not set and the prior name stage format is used.

This also removes the username component that is always added to
Stage paths on Windows (if users want to include this, they can
add it to the `build_stage`).

5 files changed, 21 insertions, 6 deletions

diff --git a/etc/spack/defaults/windows/config.yaml b/etc/spack/defaults/windows/config.yaml
index 367bf831cf..53116391cc 100644
--- a/etc/spack/defaults/windows/config.yaml
+++ b/etc/spack/defaults/windows/config.yaml
@@ -3,3 +3,4 @@ config:
   concretizer: clingo
   build_stage::
     - '$spack/.staging'
+  stage_name: '{name}-{version}-{hash:7}'
diff --git a/lib/spack/spack/package_base.py b/lib/spack/spack/package_base.py
index 470a41c460..98bf4d9c23 100644
--- a/lib/spack/spack/package_base.py
+++ b/lib/spack/spack/package_base.py
@@ -57,7 +57,7 @@ import spack.util.web
 from spack.filesystem_view import YamlFilesystemView
 from spack.install_test import TestFailure, TestSuite
 from spack.installer import InstallError, PackageInstaller
-from spack.stage import ResourceStage, Stage, StageComposite, stage_prefix
+from spack.stage import ResourceStage, Stage, StageComposite, compute_stage_name
 from spack.util.executable import ProcessError, which
 from spack.util.package_hash import package_hash
 from spack.util.prefix import Prefix
@@ -1022,8 +1022,7 @@ class PackageBase(WindowsRPath, PackageViewMixin, metaclass=PackageMeta):
         )
         # Construct a path where the stage should build..
         s = self.spec
-        stage_name = "{0}{1}-{2}-{3}".format(stage_prefix, s.name, s.version, s.dag_hash())
-
+        stage_name = compute_stage_name(s)
         stage = Stage(
             fetcher,
             mirror_paths=mirror_paths,
diff --git a/lib/spack/spack/schema/config.py b/lib/spack/spack/schema/config.py
index abe207cac0..106e45ce7a 100644
--- a/lib/spack/spack/schema/config.py
+++ b/lib/spack/spack/schema/config.py
@@ -61,6 +61,7 @@ properties = {
             "build_stage": {
                 "oneOf": [{"type": "string"}, {"type": "array", "items": {"type": "string"}}]
             },
+            "stage_name": {"type": "string"},
             "test_stage": {"type": "string"},
             "extensions": {"type": "array", "items": {"type": "string"}},
             "template_dirs": {"type": "array", "items": {"type": "string"}},
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index f6ed3c1ef4..97e05f365e 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -35,6 +35,7 @@ import spack.error
 import spack.fetch_strategy as fs
 import spack.mirror
 import spack.paths
+import spack.spec
 import spack.util.lock
 import spack.util.path as sup
 import spack.util.pattern as pattern
@@ -49,6 +50,13 @@ _source_path_subdir = "spack-src"
 stage_prefix = "spack-stage-"
 
 
+def compute_stage_name(spec):
+    """Determine stage name given a spec"""
+    default_stage_structure = "spack-stage-{name}-{version}-{hash}"
+    stage_name_structure = spack.config.get("config:stage_name", default=default_stage_structure)
+    return spec.format(format_string=stage_name_structure)
+
+
 def create_stage_root(path: str) -> None:
     """Create the stage root directory and ensure appropriate access perms."""
     assert os.path.isabs(path) and len(path.strip()) > 1
@@ -150,7 +158,10 @@ def _resolve_paths(candidates):
 
         # Ensure the path is unique per user.
         can_path = sup.canonicalize_path(path)
-        if user not in can_path:
+        # When multiple users share a stage root, we can avoid conflicts between
+        # them by adding a per-user subdirectory.
+        # Avoid doing this on Windows to keep stage absolute path as short as possible.
+        if user not in can_path and not sys.platform == "win32":
             can_path = os.path.join(can_path, user)
 
         paths.append(can_path)
diff --git a/lib/spack/spack/test/stage.py b/lib/spack/spack/test/stage.py
index 1cc1f20472..f790a66d0e 100644
--- a/lib/spack/spack/test/stage.py
+++ b/lib/spack/spack/test/stage.py
@@ -765,8 +765,11 @@ class TestStage(object):
 
         # resolved path without user appends user
         paths = [os.path.join(os.path.sep, "a", "b", "c")]
+        can_paths = [paths[0]]
         user = getpass.getuser()
-        can_paths = [os.path.join(paths[0], user)]
+
+        if sys.platform != "win32":
+            can_paths = [os.path.join(paths[0], user)]
         assert spack.stage._resolve_paths(paths) == can_paths
 
         # resolved path with node including user does not append user
@@ -789,7 +792,7 @@ class TestStage(object):
             res_paths[1] = can_tempdir
             res_paths[2] = os.path.join(can_tempdir, user)
             res_paths[3] = os.path.join(can_tempdir, "stage", user)
-        else:
+        elif sys.platform != "win32":
             res_paths[0] = os.path.join(res_paths[0], user)
 
         assert spack.stage._resolve_paths(paths) == res_paths