Switch to predetermined `constraint_value` targets

lib/BUILD

@@ -20,6 +20,7 @@ bzl_library(
     srcs = ["compatibility.bzl"],
     deps = [
         ":selects",
+        "//lib/compatibility:defs",
     ],
 )
 

lib/compatibility.bzl

@@ -10,51 +10,7 @@ more information.
 """
 
 load(":selects.bzl", "selects")
-
-def _get_name_from_target_list(targets, joiner = " or "):
-    """Join a list of strings into a string which is suitable as a target name.
-
-    The return value has a hash appended so that it is different between multiple "targets" values
-    that have the same name portion. For readability, we keep only the name portion of the
-    specified targets. But for uniqueness we need the hash. For example, the following two calls
-    may return strings as follows. The hashes are arbitrary in this example.
-
-        >>> _get_name_from_target_list(["@platforms//os:linux", "@platforms//cpu:x86_64"])
-        "linux or x86_64 (3ef2349)"
-        >>> _get_name_from_target_list(["//some/custom:linux", "//some/custom:x86_64"])
-        "linux or x86_64 (98ab64)"
-
-    Args:
-      targets: A list of target names.
-      joiner: An optional string to use for joining the list.
-
-    Returns:
-      A string which is a valid target name.
-    """
-
-    # Compute absolute labels from the user-specified ones. They can be
-    # relative or absolute. We do this to make the final name as unique as
-    # possible via a hash.
-    package_label = Label("//" + native.package_name())
-    absolute_targets = sorted([package_label.relative(target) for target in targets])
-    joined_names = joiner.join([target.name for target in absolute_targets])
-    name = "%s (%x)" % (joined_names, hash(str(absolute_targets)))
-    return name
-
-def _maybe_make_unique_incompatible_value(name):
-    """Creates a `native.constraint_value` which is "incompatible."
-
-    When composing selects which could all resolve to "incompatible" we need distinct labels.
-    This will create a `constraint_value` with the given name, if it does not already exist.
-
-    Args:
-      name: A target name to check and use.
-    """
-    if not native.existing_rule(name):
-        native.constraint_value(
-            name = name,
-            constraint_setting = "@platforms//:incompatible_setting",
-        )
+load("//lib/compatibility:defs.bzl", "MAX_NUM_ALL_OF_SETTINGS")
 
 def _none_of(*settings):
     """Create a `select()` for `target_compatible_with` which matches none of the given settings.
@@ -83,12 +39,9 @@ def _none_of(*settings):
     Returns:
       A native `select()` which maps any of the settings to the incompatible target.
     """
-    compat_name = " incompatible with " + _get_name_from_target_list(settings)
-    _maybe_make_unique_incompatible_value(compat_name)
-
     return selects.with_or({
         "//conditions:default": [],
-        tuple(settings): [":" + compat_name],
+        tuple(settings): ["@bazel_skylib//lib/compatibility:none_of"],
     })
 
 def _any_of(*settings):
@@ -118,12 +71,9 @@ def _any_of(*settings):
     Returns:
       A native `select()` which maps any of the settings an empty list.
     """
-    compat_name = " compatible with any of " + _get_name_from_target_list(settings)
-    _maybe_make_unique_incompatible_value(compat_name)
-
     return selects.with_or({
         tuple(settings): [],
-        "//conditions:default": [":" + compat_name],
+        "//conditions:default": ["@bazel_skylib//lib/compatibility:any_of"],
     })
 
 def _all_of(*settings):
@@ -160,23 +110,18 @@ def _all_of(*settings):
       *settings: The `config_setting` or `constraint_value` targets.
 
     Returns:
-      A native `select()` which is "incompatible" unless all settings are true.
+      A native series of `select()`s. The result is "incompatible" unless all settings are true.
     """
-    group_name = _get_name_from_target_list(settings, joiner = " and ")
-    compat_name = " compatible with all of " + group_name
-    _maybe_make_unique_incompatible_value(compat_name)
+    if len(settings) > MAX_NUM_ALL_OF_SETTINGS:
+        fail("Cannot support more than {} arguments. Use selects.config_setting_group() instead.".format(MAX_NUM_ALL_OF_SETTINGS))
 
-    # all_of can only be accomplished with a config_setting_group.match_all.
-    if not native.existing_rule(group_name):
-        selects.config_setting_group(
-            name = group_name,
-            match_all = settings,
-        )
-
-    return select({
-        ":" + group_name: [],
-        "//conditions:default": [":" + compat_name],
-    })
+    result = []
+    for i, setting in enumerate(settings):
+        result += select({
+            setting: [],
+            "//conditions:default": ["@bazel_skylib//lib/compatibility:all_of_{}".format(i)],
+        })
+    return result
 
 compatibility = struct(
     all_of = _all_of,

lib/compatibility/BUILD

@@ -0,0 +1,32 @@
+load(":defs.bzl", "MAX_NUM_ALL_OF_SETTINGS")
+load("//:bzl_library.bzl", "bzl_library")
+
+licenses(["notice"])
+
+package(default_visibility = ["//visibility:public"])
+
+bzl_library(
+    name = "defs",
+    srcs = ["defs.bzl"],
+)
+
+filegroup(
+    name = "build_file",
+    testonly = True,
+    srcs = ["BUILD"],
+)
+
+constraint_value(
+    name = "none_of",
+    constraint_setting = "@platforms//:incompatible_setting",
+)
+
+constraint_value(
+    name = "any_of",
+    constraint_setting = "@platforms//:incompatible_setting",
+)
+
+[constraint_value(
+    name = "all_of_" + str(i),
+    constraint_setting = "@platforms//:incompatible_setting",
+) for i in range(50)]

lib/compatibility/defs.bzl

@@ -0,0 +1,2 @@
+# The maximum number of arguments we support for compatibility.all_of().
+MAX_NUM_ALL_OF_SETTINGS = 50

tests/BUILD

@@ -98,6 +98,7 @@ sh_test(
     data = [
         ":unittest.bash",
         "//lib:compatibility",
+        "//lib/compatibility:build_file",
     ],
     tags = ["local"],
     deps = [

tests/compatibility_test.sh

@@ -67,11 +67,21 @@ EOF
 workspace(name = 'bazel_skylib')
 EOF
 
+  cat > BUILD <<EOF
+EOF
+  cat > bzl_library.bzl <<EOF
+def bzl_library(**kwargs):
+    """A dummy implementation of bzl_library()."""
+    pass
+EOF
+
   mkdir -p lib
   cat > lib/BUILD <<EOF
 EOF
 
-  for file in compatibility.bzl selects.bzl; do
+  for file in compatibility.bzl selects.bzl compatibility/BUILD compatibility/defs.bzl; do
+    mkdir -p "$(dirname "lib/${file}")" \
+      || fail "couldn't mkdir for ${file}"
     ln -sf "$(rlocation "bazel_skylib/lib/${file}")" "lib/${file}" \
       || fail "couldn't symlink ${file}."
   done
@@ -217,7 +227,7 @@ EOF
 
   ensure_that_target_doesnt_build_for_platforms \
     //target_skipping:pass_on_foo1_or_foo2_but_not_on_foo3 \
-    "didn't satisfy constraint //target_skipping: compatible with any of foo1 or foo2 (" \
+    "didn't satisfy constraint //lib/compatibility:any_of$" \
     //target_skipping:foo3_platform \
     //target_skipping:bar1_platform
 }
@@ -240,7 +250,7 @@ EOF
 
   ensure_that_target_doesnt_build_for_platforms \
     //target_skipping:pass_on_everything_but_foo1_and_foo2 \
-    "didn't satisfy constraint //target_skipping: incompatible with foo1 or foo2 (" \
+    "didn't satisfy constraint //lib/compatibility:none_of$" \
     //target_skipping:foo1_bar1_platform \
     //target_skipping:foo2_bar1_platform \
     //target_skipping:foo2_bar2_platform
@@ -263,7 +273,7 @@ EOF
 
   ensure_that_target_doesnt_build_for_platforms \
     //target_skipping:pass_on_only_foo1_and_bar1 \
-    "didn't satisfy constraint //target_skipping: compatible with all of bar1 and foo1 (" \
+    "didn't satisfy constraints\\? \\[\\?//lib/compatibility:all_of_" \
     //target_skipping:foo2_bar1_platform \
     //target_skipping:foo2_bar2_platform \
     //target_skipping:foo3_platform \
@@ -291,24 +301,23 @@ EOF
 
   ensure_that_target_doesnt_build_for_platforms \
     //target_skipping:pass_on_foo1_or_foo2_but_not_bar1 \
-    "didn't satisfy constraint //target_skipping: incompatible with bar1 (" \
+    "didn't satisfy constraint //lib/compatibility:none_of$" \
     //target_skipping:foo1_bar1_platform \
-    //target_skipping:foo2_bar1_platform \
+    //target_skipping:foo2_bar1_platform
 
   ensure_that_target_doesnt_build_for_platforms \
     //target_skipping:pass_on_foo1_or_foo2_but_not_bar1 \
-    "didn't satisfy constraint //target_skipping: compatible with any of foo1 or foo2 (" \
+    "didn't satisfy constraint //lib/compatibility:any_of$" \
     //target_skipping:foo3_platform
 
   ensure_that_target_doesnt_build_for_platforms \
     //target_skipping:pass_on_foo1_or_foo2_but_not_bar1 \
-    "didn't satisfy constraints \\[" \
+    "didn't satisfy constraints \\[//lib/compatibility:" \
     //target_skipping:bar1_platform
-
   # Since the order of constraints isn't guaranteed until
   # 72787a1267a6087923aca83bf161f93c0a1323e0, we do two individual checks here.
-  expect_log "//target_skipping: compatible with any of foo1 or foo2 ("
-  expect_log "//target_skipping: incompatible with bar1 ("
+  expect_log "//lib/compatibility:any_of\\>"
+  expect_log "//lib/compatibility:none_of\\>"
 }
 
 cd "$TEST_TMPDIR"