fix: add support for --incompatible_use_plus_in_repo_names

It was [found][1] the `~` character slows down C/C++ includes on Windows.

Bazel 8 will change to the `+` symbol.

The [--incompatible_use_plus_in_repo_names][2] flag allows testing this early.

This patch supports any separator.

[1]: bazelbuild/bazel#22865
[2]: bazelbuild/bazel#23127

Author: mattyclarkson

e2e/MODULE.bazel.lock

@@ -1,3 +1,4 @@
+load("//toolchain:separator.bzl", "SEPARATOR")
 load(":resolve.bzl", resolve = "key")
 
 visibility("//toolchain/...")
@@ -32,10 +33,8 @@ toolchian_local_select(
 }
 
 def canonical(rctx, label):
-    # This is _flaky_, it depends on `MODULE.bazel` repository naming[1]
-    # [1]: https://bazel.build/external/extension#repository_names_and_visibility
-    prefix = "~".join(rctx.name.split("~")[:-1])
-    return "@@{}~{}".format(prefix, label.removeprefix("@"))
+    prefix = SEPARATOR.join(rctx.name.split(SEPARATOR)[:-1])
+    return "@@{}{}{}".format(prefix, SEPARATOR, label.removeprefix("@"))
 
 def implementation(rctx):
     label = resolve(rctx.attr.map, no_match_error = rctx.attr.no_match_error)

toolchain/local/select/repository.bzl

@@ -1,3 +1,4 @@
+load("//toolchain:separator.bzl", "SEPARATOR")
 load("//toolchain/local/select:resolve.bzl", resolve = "value")
 
 visibility("//toolchain/...")
@@ -56,8 +57,9 @@ ATTRS = {
 }
 
 def implementation(rctx):
-    program = rctx.attr.program or rctx.attr.name.rsplit("~", 1)[1].removeprefix("which-")
-    target = rctx.attr.target or rctx.attr.name.rsplit("~", 1)[1]
+    name = rctx.attr.name.rsplit(SEPARATOR, 1)[1]
+    program = rctx.attr.program or name.removeprefix("which-")
+    target = rctx.attr.target or name
     basename = rctx.attr.basename or program
     variable = rctx.attr.variable or basename.upper()
     entrypoint = resolve(rctx.attr.entrypoint)

toolchain/local/which/repository.bzl

@@ -1,3 +1,4 @@
+load("//toolchain:separator.bzl", "SEPARATOR")
 load("//toolchain:resolved.bzl", _ATTRS = "ATTRS")
 
 visibility("//toolchain/...")
@@ -33,7 +34,7 @@ ATTRS = _ATTRS | {
 }
 
 def implementation(rctx):
-    target = rctx.attr.target or rctx.attr.name.rsplit("~", 1)[1]
+    target = rctx.attr.target or rctx.attr.name.rsplit(SEPARATOR, 1)[1]
     basename = rctx.attr.basename or target.removeprefix("resolved-")
     substitutions = {
         "{{toolchain_type}}": str(rctx.attr.toolchain_type),

toolchain/resolved/repository.bzl

@@ -0,0 +1,3 @@
+visibility("//...")
+
+SEPARATOR = Label("@local").workspace_name.removesuffix("local")[-1]