Add simple_variables option back to compile_cel_policy and CelPolicyCompilerTool

policy/src/main/java/dev/cel/policy/tools/CelPolicyCompilerTool.java

@@ -120,6 +120,11 @@ public final class CelPolicyCompilerTool implements Callable<Integer> {
       description = "Optimize field selection for version skew mitigation")
   private boolean optimizeFieldSelection = false;
 
+  @Option(
+      names = {"--simple_variables"},
+      description = "Enable inline variable definitions (e.g., '- var_name: expr') in the policy")
+  private boolean simpleVariables = false;
+
   private static final CelOptions CEL_OPTIONS =
       CelOptions.current()
           .populateMacroCalls(true)
@@ -195,7 +200,9 @@ public Integer call() {
     CelPolicy policy;
     try {
       CelPolicyParser policyParser =
-          CelPolicyParserFactory.newYamlParserBuilder().enableSimpleVariables(true).build();
+          CelPolicyParserFactory.newYamlParserBuilder()
+              .enableSimpleVariables(simpleVariables)
+              .build();
       String policyYaml = new String(readFileBytes(effectivePolicyPath), UTF_8);
       policy = policyParser.parse(policyYaml, effectivePolicyPath);
     } catch (Exception e) {

policy/src/test/java/dev/cel/policy/tools/BUILD.bazel

@@ -19,6 +19,7 @@ compile_cel_policy(
     optimize_field_selection = True,
     policy = ":test_policy.yaml",
     proto_srcs = ["@cel_spec//proto/cel/expr/conformance/proto3:test_all_types_proto"],
+    simple_variables = True,
 )
 
 java_library(
@@ -28,7 +29,6 @@ java_library(
     data = [
         ":compiled_test_policy.binarypb",
         ":test_all_types_fds",
-        ":test_policy.yaml",
         "//testing/environment:proto3_message_variables",
     ],
     deps = [

policy/src/test/java/dev/cel/policy/tools/CelPolicyCompilerToolTest.java

@@ -233,6 +233,39 @@ public void compile_withBaseConfig_success() throws Exception {
     assertThat(result).isEqualTo(Optional.of(true));
   }
 
+  @Test
+  public void compile_withVariables_success() throws Exception {
+    String configPath = createFile("config.yaml", "name: test-env\n");
+    String policyPath =
+        createFile(
+            "policy.yaml",
+            "name: p\n"
+                + "rule:\n"
+                + "  variables:\n"
+                + "    - name: my_sum\n"
+                + "      expression: 10 + 20\n"
+                + "  match:\n"
+                + "    - condition: variables.my_sum == 30\n"
+                + "      output: 'true'\n");
+    File outputFile = tempFolder.newFile("output.binarypb");
+    CommandLine cmd = new CommandLine(new CelPolicyCompilerTool());
+
+    int exitCode =
+        cmd.execute(
+            "--policy",
+            policyPath,
+            "--config",
+            configPath,
+            "--output",
+            outputFile.getAbsolutePath());
+
+    assertThat(exitCode).isEqualTo(0);
+    CheckedExpr checkedExpr =
+        CheckedExpr.parseFrom(Files.toByteArray(outputFile), ExtensionRegistry.getEmptyRegistry());
+    CelAbstractSyntaxTree ast = CelProtoAbstractSyntaxTree.fromCheckedExpr(checkedExpr).getAst();
+    assertThat(celRuntime.createProgram(ast).eval()).isEqualTo(Optional.of(true));
+  }
+
   @Test
   public void compile_withSimpleVariables_success() throws Exception {
     String configPath = createFile("config.yaml", "name: test-env\n");
@@ -246,26 +279,24 @@ public void compile_withSimpleVariables_success() throws Exception {
                 + "  match:\n"
                 + "    - condition: variables.my_sum == 30\n"
                 + "      output: 'true'\n");
-
     File outputFile = tempFolder.newFile("output.binarypb");
-
     CommandLine cmd = new CommandLine(new CelPolicyCompilerTool());
+
     int exitCode =
         cmd.execute(
             "--policy",
             policyPath,
             "--config",
             configPath,
+            "--simple_variables",
             "--output",
             outputFile.getAbsolutePath());
 
     assertThat(exitCode).isEqualTo(0);
-
     CheckedExpr checkedExpr =
         CheckedExpr.parseFrom(Files.toByteArray(outputFile), ExtensionRegistry.getEmptyRegistry());
     CelAbstractSyntaxTree ast = CelProtoAbstractSyntaxTree.fromCheckedExpr(checkedExpr).getAst();
-    Object result = celRuntime.createProgram(ast).eval();
-    assertThat(result).isEqualTo(Optional.of(true));
+    assertThat(celRuntime.createProgram(ast).eval()).isEqualTo(Optional.of(true));
   }
 
   @Test

policy/src/test/java/dev/cel/policy/tools/test_policy.yaml

@@ -1,7 +1,9 @@
 # Copyright 2026 Google LLC
 name: "test_policy"
 rule:
+  variables:
+    - is_valid_int: proto3.single_int32 == 100
   match:
-    - condition: proto3.single_int32 == 100 && has(proto3.single_nested_message)
+    - condition: variables.is_valid_int && has(proto3.single_nested_message)
       output: '"ALLOW"'
     - output: '"DENY"'

policy/tools/BUILD.bazel

@@ -22,6 +22,5 @@ alias(
 bzl_library(
     name = "compile_cel_policy_bzl",
     srcs = ["compile_cel_policy.bzl"],
-    visibility = ["//visibility:private"],
     deps = ["@rules_proto//proto:defs"],
 )

policy/tools/compile_cel_policy.bzl

@@ -26,6 +26,7 @@ def compile_cel_policy(
         output_format = "binarypb",
         output_version = "canonical",
         optimize_field_selection = False,
+        simple_variables = False,
         visibility = None):
     """Compiles a CEL policy into a CheckedExpr binarypb or textpb with optional select optimization.
 
@@ -43,7 +44,13 @@ def compile_cel_policy(
       output: (optional) str file name for the output checked expression (default derived from label name and format)
       output_format: (optional) str either "binarypb", "textpb", or "textproto" (default "binarypb")
       output_version: (optional) str either "canonical" or "v1alpha1" (default "canonical")
-      optimize_field_selection: (optional) bool whether to enable AST select optimization (default False)
+      optimize_field_selection: (optional) bool whether to enable AST select optimization (default False).
+        When True, embeds field numbers, wire types, and default values directly into the compiled
+        `CheckedExpr` AST. This enables version-skew and field-rename resilience (evaluating unknown
+        fields from raw wire bytes on older clients) and faster field selections, at the cost of a
+        larger serialized AST payload.
+      simple_variables: (optional) bool whether to enable inline variable definitions (e.g.,
+        `- var_name: expr` instead of `- name: var_name` / `expression: expr`) in the policy (default False)
       visibility: (optional) visibility to use on the genrule macro (default None)
     """
     if output_format not in ("binarypb", "textpb", "textproto"):
@@ -87,6 +94,9 @@ def compile_cel_policy(
     if optimize_field_selection:
         args.append("--optimize_field_selection")
 
+    if simple_variables:
+        args.append("--simple_variables")
+
     cmd = (
         "$(location //policy/tools:cel_policy_compiler_tool) " +
         " ".join(args)