Move scala_toolchains to scala/toolchains.bzl

Removes this symbol from `scala/scala.bzl` as well as
`setup_scala_testing_toolchain`, and deletes
`scala/private/macros/toolchains.bzl`. Part of bazelbuild#1482 and bazelbuild#1652.

This is required for Bazel 8 and `rules_java` 8 compatibility, but is
also compatible with Bazel 6 and 7. In bazelbuild#1652, @hvadehra suggested
partitioning the `.bzl` files such that `WORKSPACE` doesn't `load` a
file that tries to `load` symbols from `rules_java`. I successfully did
so in a separate branch, and along with other minor changes, got
`rules_scala` to build with `rules_java` 8.5.1.

The other changes will come in separate pull requests, but it makes
sense to land this change now before adding any other toolchains to
`scala_toolchains`.

---

Arguably, we should remove all macros exported from `scala/scala.bzl`
that only instantiate toolchain dependencies and define toolchains. That
may be a breaking change for some users, but will ultimately be
necessary for these macros to remain compatible with Bazel 8.

WORKSPACE

@@ -30,7 +30,7 @@ load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")
 
 scala_config(enable_compiler_dependency_tracking = True)
 
-load("//scala:scala.bzl", "scala_toolchains")
+load("//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(
     fetch_sources = True,

docs/testing.md

@@ -31,7 +31,10 @@ Test framework dependencies are configured via testing toolchain. For convenienc
 `setup_scala_testing_toolchain` can be used to define such toolchains.
 
 ```starlark
-load("@io_bazel_rules_scala//scala:scala.bzl", "setup_scala_testing_toolchain")
+load(
+    "@io_bazel_rules_scala//testing:testing.bzl",
+    "setup_scala_testing_toolchain",
+)
 ```
 
 Attributes
@@ -53,7 +56,10 @@ Examples (assumes maven deps are managed with rules_jvm_external):
 
 ```starlark
 # BUILD
-load("@io_bazel_rules_scala//scala:scala.bzl", "setup_scala_testing_toolchain")
+load(
+    "@io_bazel_rules_scala//testing:testing.bzl",
+    "setup_scala_testing_toolchain",
+)
 
 setup_scala_testing_toolchain(
     name = "scalatest_toolchain",
@@ -77,7 +83,10 @@ register_toolchains('//:scalatest_toolchain')
 #### JUnit 4
 ```starlark
 # BUILD
-load("@io_bazel_rules_scala//scala:scala.bzl", "setup_scala_testing_toolchain")
+load(
+    "@io_bazel_rules_scala//testing:testing.bzl",
+    "setup_scala_testing_toolchain",
+)
 
 setup_scala_testing_toolchain(
     name = "junit_toolchain",
@@ -98,7 +107,10 @@ For Specs2 rules to work, `junit_classpath`, `specs2_junit_classpath` and `specs
 be configured.
 ```starlark
 # BUILD
-load("@io_bazel_rules_scala//scala:scala.bzl", "setup_scala_testing_toolchain")
+load(
+    "@io_bazel_rules_scala//testing:testing.bzl",
+    "setup_scala_testing_toolchain",
+)
 
 setup_scala_testing_toolchain(
     name = "specs2_toolchain",
@@ -122,4 +134,4 @@ Register the toolchain
 ```starlark
 # WORKSPACE
 register_toolchains('//:specs2_toolchain')
-```
+```

dt_patches/test_dt_patches/WORKSPACE

@@ -40,7 +40,7 @@ load("@compiler_sources//:extensions.bzl", "import_compiler_source_repos")
 
 import_compiler_source_repos()
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(
     fetch_sources = True,

dt_patches/test_dt_patches_user_srcjar/WORKSPACE

@@ -110,7 +110,7 @@ srcjars_by_version = {
     },
 }
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(
     fetch_sources = True,

examples/crossbuild/WORKSPACE

@@ -38,7 +38,7 @@ scala_config(
     ],
 )
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(scalatest = True)
 

examples/scala3/WORKSPACE

@@ -31,7 +31,7 @@ load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")
 
 scala_config(scala_version = "3.5.2")
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(fetch_sources = True)
 

examples/semanticdb/WORKSPACE

@@ -34,7 +34,7 @@ load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")
 
 scala_config(scala_version = "2.13.15")
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(fetch_sources = True)
 

examples/testing/multi_frameworks_toolchain/BUILD

@@ -1,4 +1,7 @@
-load("@io_bazel_rules_scala//scala:scala.bzl", "setup_scala_testing_toolchain")
+load(
+    "@io_bazel_rules_scala//testing:testing.bzl",
+    "setup_scala_testing_toolchain",
+)
 
 setup_scala_testing_toolchain(
     name = "testing_toolchain",

examples/testing/multi_frameworks_toolchain/WORKSPACE

@@ -31,7 +31,7 @@ load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")
 
 scala_config()
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(
     fetch_sources = True,

examples/testing/scalatest_repositories/WORKSPACE

@@ -31,7 +31,7 @@ load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")
 
 scala_config()
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(
     fetch_sources = True,

examples/testing/specs2_junit_repositories/WORKSPACE

@@ -31,7 +31,7 @@ load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")
 
 scala_config()
 
-load("@io_bazel_rules_scala//scala:scala.bzl", "scala_toolchains")
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_toolchains")
 
 scala_toolchains(
     fetch_sources = True,

scala/private/macros/toolchains_repo.bzl

@@ -120,12 +120,15 @@ load(
 """
 
 _TESTING_TOOLCHAIN_BUILD = """
-load("@@{rules_scala_repo}//scala:scala.bzl", "setup_scala_testing_toolchain")
 load("@@{rules_scala_repo}//scala:scala_cross_version.bzl", "version_suffix")
 load(
     "@@{rules_scala_repo}//testing:deps.bzl",
     "{deps_symbols}",
 )
+load(
+    "@@{rules_scala_repo}//testing:testing.bzl",
+    "setup_scala_testing_toolchain",
+)
 load("@io_bazel_rules_scala_config//:config.bzl", "SCALA_VERSIONS")
 
 [

scala/scala.bzl

@@ -2,10 +2,6 @@ load(
     "//specs2:specs2_junit.bzl",
     _specs2_junit_dependencies = "specs2_junit_dependencies",
 )
-load(
-    "//scala/private:macros/toolchains.bzl",
-    _scala_toolchains = "scala_toolchains",
-)
 load(
     "//scala/private:macros/toolchains_repo.bzl",
     _scala_toolchains_repo = "scala_toolchains_repo",
@@ -50,10 +46,6 @@ load(
     _scala_test = "scala_test",
     _scala_test_suite = "scala_test_suite",
 )
-load(
-    "//testing:testing.bzl",
-    _setup_scala_testing_toolchain = "setup_scala_testing_toolchain",
-)
 
 def scala_specs2_junit_test(name, **kwargs):
     _scala_junit_test(
@@ -87,7 +79,5 @@ rules_scala_setup = _rules_scala_setup
 rules_scala_toolchain_deps_repositories = _rules_scala_toolchain_deps_repositories
 scala_test = _scala_test
 scala_test_suite = _scala_test_suite
-setup_scala_testing_toolchain = _setup_scala_testing_toolchain
 setup_scala_toolchain = _setup_scala_toolchain
-scala_toolchains = _scala_toolchains
 scala_toolchains_repo = _scala_toolchains_repo