Intorduce flag that switches where toolchains reads config from

Unfortunately bazel rules doesn't know if attr was set by user or not
bazelbuild/bazel#14434

Author: simuons

scala/scala_toolchain.bzl

@@ -40,66 +40,80 @@ def _partition_patterns(patterns):
     ]
     return includes, excludes
 
-_deprecated_attrs = {
-    "dependency_mode": attr.string(values = ["direct", "plus-one", "transitive"]),
-    "strict_deps_mode": attr.string(values = ["off", "warn", "error", "default"]),
-    "unused_dependency_checker_mode": attr.string(values = ["off", "warn", "error"]),
-    "compiler_deps_mode": attr.string(values = ["off", "warn", "error"]),
-    "dependency_tracking_method": attr.string(values = ["ast-plus", "ast", "high-level", "default"]),
+_config_attrs = {
+    "dependency_mode": attr.string(
+        default = "direct",
+        values = ["direct", "plus-one", "transitive"],
+    ),
+    "strict_deps_mode": attr.string(
+        default = "default",
+        values = ["off", "warn", "error", "default"],
+    ),
+    "unused_dependency_checker_mode": attr.string(
+        default = "off",
+        values = ["off", "warn", "error"],
+    ),
+    "compiler_deps_mode": attr.string(
+        default = "off",
+        values = ["off", "warn", "error"],
+    ),
+    "dependency_tracking_method": attr.string(
+        default = "default",
+        values = ["ast-plus", "ast", "high-level", "default"],
+    ),
     "dependency_tracking_strict_deps_patterns": attr.string_list(
         doc = "List of target prefixes included for strict deps analysis. Exclude patterns with '-'",
+        default = [""],
     ),
     "dependency_tracking_unused_deps_patterns": attr.string_list(
         doc = "List of target prefixes included for unused deps analysis. Exclude patterns with '-'",
+        default = [""],
     ),
     "enable_diagnostics_report": attr.bool(
         doc = "Enable the output of structured diagnostics through the BEP",
     ),
     "enable_stats_file": attr.bool(
+        default = True,
         doc = "Enable writing of statsfile",
     ),
     "enable_semanticdb": attr.bool(
+        default = False,
         doc = "Enable SemanticDb",
     ),
-    "semanticdb_bundle_in_jar": attr.bool(
-        doc = "Option to bundle the semanticdb files inside the output jar file",
-    ),
+    "semanticdb_bundle_in_jar": attr.bool(default = False, doc = "Option to bundle the semanticdb files inside the output jar file"),
     "use_argument_file_in_runner": attr.bool(
+        default = False,
         doc = "Changes java binaries scripts (including tests) to use argument files and not classpath jars to improve performance, requires java > 8",
     ),
 }
 
-def _attr_to_flag(name):
-    return "//scala/settings:%s" % name
-
-_flag_attrs = {
-    "_" + k: attr.label(default = _attr_to_flag(k))
-    for k in _deprecated_attrs.keys()
+_config_flags = {
+    "_" + k: attr.label(default = "//scala/settings:%s" % k)
+    for k in _config_attrs.keys()
 }
 
-def _resolve_flags(ctx):
-    def compute(name):
-        attr = getattr(ctx.attr, name)
-        return attr if attr else getattr(ctx.attr, "_" + name)[BuildSettingInfo].value
-
-    return struct(**{k: compute(k) for k in _deprecated_attrs.keys()})
+def _config(ctx):
+    if ctx.attr._scala_toolchain_flags[BuildSettingInfo].value:
+        return struct(**{k: getattr(ctx.attr, "_" + k)[BuildSettingInfo].value for k in _config_attrs.keys()})
+    else:
+        return struct(**{k: getattr(ctx.attr, k) for k in _config_attrs.keys()})
 
 def _scala_toolchain_impl(ctx):
-    flags = _resolve_flags(ctx)
+    config = _config(ctx)
 
-    dependency_mode = flags.dependency_mode
+    dependency_mode = config.dependency_mode
 
     strict_deps_mode = _compute_strict_deps_mode(
-        flags.strict_deps_mode,
+        config.strict_deps_mode,
         dependency_mode,
     )
 
-    compiler_deps_mode = flags.compiler_deps_mode
+    compiler_deps_mode = config.compiler_deps_mode
 
-    unused_dependency_checker_mode = flags.unused_dependency_checker_mode
+    unused_dependency_checker_mode = config.unused_dependency_checker_mode
     dependency_tracking_method = _compute_dependency_tracking_method(
         dependency_mode,
-        flags.dependency_tracking_method,
+        config.dependency_tracking_method,
     )
 
     # Final quality checks to possibly detect buggy code above
@@ -118,10 +132,10 @@ def _scala_toolchain_impl(ctx):
     if "ast-plus" == dependency_tracking_method and not ENABLE_COMPILER_DEPENDENCY_TRACKING:
         fail("To use 'ast-plus' dependency tracking, you must set 'enable_compiler_dependency_tracking' to True in scala_config")
 
-    all_strict_deps_patterns = flags.dependency_tracking_strict_deps_patterns
+    all_strict_deps_patterns = config.dependency_tracking_strict_deps_patterns
     strict_deps_includes, strict_deps_excludes = _partition_patterns(all_strict_deps_patterns)
 
-    all_unused_deps_patterns = flags.dependency_tracking_unused_deps_patterns
+    all_unused_deps_patterns = config.dependency_tracking_unused_deps_patterns
     unused_deps_includes, unused_deps_excludes = _partition_patterns(all_unused_deps_patterns)
 
     toolchain = platform_common.ToolchainInfo(
@@ -138,12 +152,12 @@ def _scala_toolchain_impl(ctx):
         unused_deps_exclude_patterns = unused_deps_excludes,
         scalac_jvm_flags = ctx.attr.scalac_jvm_flags,
         scala_test_jvm_flags = ctx.attr.scala_test_jvm_flags,
-        enable_diagnostics_report = flags.enable_diagnostics_report,
+        enable_diagnostics_report = config.enable_diagnostics_report,
         jacocorunner = ctx.attr.jacocorunner,
-        enable_stats_file = flags.enable_stats_file,
-        enable_semanticdb = flags.enable_semanticdb,
-        semanticdb_bundle_in_jar = flags.semanticdb_bundle_in_jar,
-        use_argument_file_in_runner = flags.use_argument_file_in_runner,
+        enable_stats_file = config.enable_stats_file,
+        enable_semanticdb = config.enable_semanticdb,
+        semanticdb_bundle_in_jar = config.semanticdb_bundle_in_jar,
+        use_argument_file_in_runner = config.use_argument_file_in_runner,
         scala_version = ctx.attr._scala_version[BuildSettingInfo].value,
     )
     return [toolchain]
@@ -166,8 +180,8 @@ def _default_dep_providers():
 _scala_toolchain = rule(
     _scala_toolchain_impl,
     attrs = _dicts.add(
-        _deprecated_attrs,
-        _flag_attrs,
+        _config_attrs,
+        _config_flags,
         {
             "dep_providers": attr.label_list(
                 default = _default_dep_providers(),
@@ -178,6 +192,7 @@ _scala_toolchain = rule(
             "scalac_jvm_flags": attr.string_list(),
             "scala_test_jvm_flags": attr.string_list(),
             "_scala_version": attr.label(default = "@io_bazel_rules_scala_config//:scala_version"),
+            "_scala_toolchain_flags": attr.label(default = "//scala/settings:scala_toolchain_flags"),
         },
     ),
     fragments = ["java"],

scala/settings/BUILD

@@ -9,6 +9,11 @@ stamp_scala_import(
 
 load("@bazel_skylib//rules:common_settings.bzl", "bool_flag", "string_flag", "string_list_flag")
 
+bool_flag(
+    name = "scala_toolchain_flags",
+    build_setting_default = False,
+)
+
 string_flag(
     name = "dependency_mode",
     build_setting_default = "direct",