Reject empty separator in string.split

Related: #7355 #8726

Closes #8836.

PiperOrigin-RevId: 257614252

src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java

diff --git a/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java b/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java
index 6aa2045..3d50b23 100644
--- a/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java
+++ b/src/test/java/com/google/devtools/build/lib/packages/SkylarkSemanticsConsistencyTest.java
@@ -145,8 +145,9 @@
         "--incompatible_disallow_legacy_javainfo=" + rand.nextBoolean(),
         "--incompatible_disallow_legacy_java_provider=" + rand.nextBoolean(),
         "--incompatible_disallow_old_style_args_add=" + rand.nextBoolean(),
-        "--incompatible_disallow_struct_provider_syntax=" + rand.nextBoolean(),
         "--incompatible_disallow_rule_execution_platform_constraints_allowed=" + rand.nextBoolean(),
+        "--incompatible_disallow_split_empty_separator=" + rand.nextBoolean(),
+        "--incompatible_disallow_struct_provider_syntax=" + rand.nextBoolean(),
         "--incompatible_do_not_split_linking_cmdline=" + rand.nextBoolean(),
         "--incompatible_expand_directories=" + rand.nextBoolean(),
         "--incompatible_new_actions_api=" + rand.nextBoolean(),
@@ -198,8 +199,9 @@
         .incompatibleDisallowLegacyJavaInfo(rand.nextBoolean())
         .incompatibleDisallowLegacyJavaProvider(rand.nextBoolean())
         .incompatibleDisallowOldStyleArgsAdd(rand.nextBoolean())
-        .incompatibleDisallowStructProviderSyntax(rand.nextBoolean())
         .incompatibleDisallowRuleExecutionPlatformConstraintsAllowed(rand.nextBoolean())
+        .incompatibleDisallowSplitEmptySeparator(rand.nextBoolean())
+        .incompatibleDisallowStructProviderSyntax(rand.nextBoolean())
         .incompatibleDoNotSplitLinkingCmdline(rand.nextBoolean())
         .incompatibleExpandDirectories(rand.nextBoolean())
         .incompatibleNewActionsApi(rand.nextBoolean())

src/test/java/com/google/devtools/build/lib/skylark/SkylarkIntegrationTest.java

diff --git a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkIntegrationTest.java b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkIntegrationTest.java
index f78d647..5a913d9 100644
--- a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkIntegrationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkIntegrationTest.java
@@ -3100,6 +3100,30 @@
   }
 
   @Test
+  public void testSplitEmptySeparatorForbidden() throws Exception {
+    setSkylarkSemanticsOptions("--incompatible_disallow_split_empty_separator=true");
+
+    scratch.file("test/extension.bzl", "y = 'abc'.split('')");
+
+    scratch.file("test/BUILD", "load('//test:extension.bzl', 'y')", "cc_library(name = 'r')");
+
+    reporter.removeHandler(failFastHandler);
+    getConfiguredTarget("//test:r");
+    assertContainsEvent("Empty separator");
+  }
+
+  @Test
+  public void testSplitEmptySeparator() throws Exception {
+    setSkylarkSemanticsOptions("--incompatible_disallow_split_empty_separator=false");
+
+    scratch.file("test/extension.bzl", "y = 'abc'.split('')");
+
+    scratch.file("test/BUILD", "load('//test:extension.bzl', 'y')", "cc_library(name = 'r')");
+
+    getConfiguredTarget("//test:r");
+  }
+
+  @Test
   public void testNoOutputsError() throws Exception {
     scratch.file(
         "test/skylark/test_rule.bzl",