Null variant labels (#110)

* Add a `get_variant_label()` helper

* Use 'null' label for the null variant

* Use `sha256("")` for null variant hash

Since we are no longer using it as a label, we do not need
a recognizable special value here.  Instead, just use hash of an empty
string, so we can remove the special casing in code.

* Restore explicit checks for `--variant-label` use

* Remove `NULL_VARIANT_HASH`

Remove `NULL_VARIANT_HASH` since it resembles magic constant too much.
In the few places where we need it, either call hash directly, or get
it from VariantDescription.

Signed-off-by: Michał Górny <[email protected]>

Author: mgorny

tests/artifacts/test-package/dist/test_package-0-py3-none-any-00000000.whl

@@ -20,7 +20,7 @@
         }
     },
     "variants": {
-        "00000000": {},
+        "null": {},
         "5d8be4b9": {
             "installable_plugin": {
                 "feat1": [

tests/artifacts/test-package/dist/test_package-0-py3-none-any-null.whl

@@ -75,7 +75,7 @@
                 ]
             }
         },
-        "00000000": {},
+        "null": {},
         "3f7188c1": {
             "fictional_hw": {
                 "architecture": [

tests/artifacts/test-package/dist/test_package-0-variants.json

@@ -23,7 +23,7 @@
         }
     },
     "variants": {
-        "00000000": {},
+        "null": {},
         "38ea48ce": {
             "fictional_hw": {
                 "architecture": [
@@ -69,4 +69,4 @@
             }
         }
     }
-}
+}

tests/artifacts/variant_json_files/dummy_project-1.0.0-variants.json

@@ -3,7 +3,7 @@
 from typing import TYPE_CHECKING
 
 from variantlib.commands.main import main
-from variantlib.constants import NULL_VARIANT_HASH
+from variantlib.constants import NULL_VARIANT_LABEL
 
 if TYPE_CHECKING:
     import pytest
@@ -34,13 +34,13 @@ def test_analyze_wheel_null_variant(
             "analyze-wheel",
             "-i",
             "tests/artifacts/test-package/dist/test_package-0-py3-none-any-"
-            f"{NULL_VARIANT_HASH}.whl",
+            f"{NULL_VARIANT_LABEL}.whl",
         ]
     )
     assert (
         capsys.readouterr().out
         == f"""\
-############################## Variant: `{NULL_VARIANT_HASH}` \
+############################## Variant: `{NULL_VARIANT_LABEL}` \
 #############################
 ################################################################################
 """

tests/artifacts/variant_json_files/sandbox_project-1.0.0-variants.json

@@ -6,7 +6,7 @@
 from typing import TYPE_CHECKING
 
 from variantlib.commands.main import main
-from variantlib.constants import NULL_VARIANT_HASH
+from variantlib.constants import NULL_VARIANT_LABEL
 from variantlib.constants import VARIANT_INFO_DEFAULT_PRIO_KEY
 from variantlib.constants import VARIANT_INFO_NAMESPACE_KEY
 from variantlib.constants import VARIANT_INFO_PROVIDER_DATA_KEY
@@ -25,7 +25,7 @@ def test_generate_index_json(
 ) -> None:
     filenames = [
         "test_package-0-py3-none-any.whl",
-        f"test_package-0-py3-none-any-{NULL_VARIANT_HASH}.whl",
+        f"test_package-0-py3-none-any-{NULL_VARIANT_LABEL}.whl",
         "test_package-0-py3-none-any-5d8be4b9.whl",
     ]
     artifact_dir = Path("tests/artifacts/test-package/dist")
@@ -51,7 +51,7 @@ def test_generate_index_json(
             },
         },
         VARIANTS_JSON_VARIANT_DATA_KEY: {
-            NULL_VARIANT_HASH: {},
+            NULL_VARIANT_LABEL: {},
             "5d8be4b9": {
                 "installable_plugin": {
                     "feat1": ["val1c"],

tests/commands/test_analyze_wheel.py

@@ -1,17 +1,18 @@
 from __future__ import annotations
 
+import hashlib
 from itertools import chain
 
 import pytest
 
 from variantlib.commands.main import main
-from variantlib.constants import NULL_VARIANT_HASH
+from variantlib.constants import VARIANT_HASH_LEN
 
 
 @pytest.mark.parametrize(
     ("properties", "expected"),
     [
-        ([], NULL_VARIANT_HASH),
+        ([], hashlib.sha256(b"").hexdigest()[:VARIANT_HASH_LEN]),
         (["a::b::c"], "01a9783a"),
         (["d::e::f"], "41665eee"),
         (["a::b::c", "d::e::f"], "eb9a66a7"),

tests/commands/test_generate_index_json.py

@@ -7,7 +7,7 @@
 
 from tests.utils import assert_zips_equal
 from variantlib.commands.main import main
-from variantlib.constants import NULL_VARIANT_HASH
+from variantlib.constants import NULL_VARIANT_LABEL
 
 if TYPE_CHECKING:
     from pathlib import Path
@@ -37,7 +37,7 @@ def mocked_plugin_reqs(
     ("label", "properties"),
     [
         # Null Variant
-        (NULL_VARIANT_HASH, None),
+        (NULL_VARIANT_LABEL, None),
         # Variant 1
         (
             "5d8be4b9",
@@ -86,7 +86,7 @@ def test_make_variant(
             itertools.chain.from_iterable(["-p", vprop] for vprop in properties)
         )
 
-    if len(label) != 8:
+    if len(label) != 8 and label != "null":
         cmd_args.append(f"--variant-label={label}")
 
     main([*cmd_args])
@@ -112,9 +112,13 @@ def test_make_variant(
             ["--property=x::y::z", "--variant-label=123456789"],
             "error: invalid variant label",
         ),
+        (
+            ["--property=x::y::z", "--variant-label=null"],
+            "error: invalid variant label",
+        ),
         (
             ["--null-variant", "--variant-label=null"],
-            "error: --variant-label cannot be usedwith --null-variant",
+            "error: --variant-label cannot be used with --null-variant",
         ),
     ],
 )

tests/commands/test_get_variant_hash.py

@@ -6,13 +6,13 @@
 
 from tests.utils import assert_zips_equal
 from variantlib.commands.main import main
-from variantlib.constants import NULL_VARIANT_HASH
+from variantlib.constants import NULL_VARIANT_LABEL
 
 
 @pytest.mark.parametrize(
     "filename",
     [
-        f"test_package-0-py3-none-any-{NULL_VARIANT_HASH}.whl",
+        f"test_package-0-py3-none-any-{NULL_VARIANT_LABEL}.whl",
         "test_package-0-py3-none-any-5d8be4b9.whl",
         "test_package-0-py3-none-any-60567bd9.whl",
         "test_package-0-py3-none-any-fbe82642.whl",