Add late bound function resolver to lite runtime's program interface

runtime/BUILD.bazel

@@ -51,25 +51,19 @@ java_library(
 
 java_library(
     name = "function_binding",
-    exports = [
-        "//runtime/src/main/java/dev/cel/runtime:function_binding",
-    ],
+    exports = ["//runtime/src/main/java/dev/cel/runtime:function_binding"],
 )
 
 cel_android_library(
     name = "function_binding_android",
-    exports = [
-        "//runtime/src/main/java/dev/cel/runtime:function_binding_android",
-    ],
+    exports = ["//runtime/src/main/java/dev/cel/runtime:function_binding_android"],
 )
 
 java_library(
     name = "function_overload_impl",
     # used_by_android
     visibility = ["//:internal"],
-    exports = [
-        "//runtime/src/main/java/dev/cel/runtime:function_overload_impl",
-    ],
+    exports = ["//runtime/src/main/java/dev/cel/runtime:function_overload_impl"],
 )
 
 java_library(

runtime/src/main/java/dev/cel/runtime/BUILD.bazel

@@ -448,7 +448,6 @@ java_library(
 
 # keep sorted
 RUNTIME_SOURCES = [
-    "CelFunctionResolver.java",
     "CelLateFunctionBindings.java",
     "CelResolvedOverload.java",
     "CelRuntime.java",
@@ -603,6 +602,19 @@ cel_android_library(
     ],
 )
 
+java_library(
+    name = "function_resolver",
+    srcs = ["CelFunctionResolver.java"],
+    # used_by_android
+    tags = [
+    ],
+    deps = [
+        ":function_overload_impl",
+        "@maven//:com_google_code_findbugs_annotations",
+        "@maven//:com_google_errorprone_error_prone_annotations",
+    ],
+)
+
 java_library(
     name = "function_overload",
     srcs = [
@@ -652,6 +664,7 @@ java_library(
         ":function_binding",
         ":function_overload",
         ":function_overload_impl",
+        ":function_resolver",
         ":interpretable",
         ":interpreter",
         ":lite_runtime",
@@ -689,6 +702,7 @@ java_library(
     deps = [
         ":evaluation_exception",
         ":function_binding",
+        ":function_resolver",
         ":standard_functions",
         "//:auto_value",
         "//common:cel_ast",
@@ -710,7 +724,9 @@ java_library(
         ":cel_value_runtime_type_provider",
         ":dispatcher",
         ":evaluation_exception",
+        ":evaluation_listener",
         ":function_binding",
+        ":function_resolver",
         ":interpretable",
         ":interpreter",
         ":lite_runtime",
@@ -738,7 +754,9 @@ cel_android_library(
         ":cel_value_runtime_type_provider_android",
         ":dispatcher_android",
         ":evaluation_exception",
+        ":evaluation_listener_android",
         ":function_binding_android",
+        ":function_resolver",
         ":interpretable_android",
         ":interpreter_android",
         ":lite_runtime_android",
@@ -923,8 +941,7 @@ java_library(
 cel_android_library(
     name = "evaluation_listener_android",
     srcs = ["CelEvaluationListener.java"],
-    tags = [
-    ],
+    visibility = ["//visibility:private"],
     deps = [
         "//common/ast:ast_android",
         "@maven//:com_google_code_findbugs_annotations",
@@ -940,6 +957,7 @@ cel_android_library(
     deps = [
         ":evaluation_exception",
         ":function_binding_android",
+        ":function_resolver",
         ":standard_functions_android",
         "//:auto_value",
         "//common:cel_ast_android",

runtime/src/main/java/dev/cel/runtime/CelLiteRuntime.java

@@ -36,8 +36,18 @@ public interface CelLiteRuntime {
   /** Creates an evaluable {@code Program} instance which is thread-safe and immutable. */
   @Immutable
   interface Program {
+
+    /** Evaluate the expression without any variables. */
     Object eval() throws CelEvaluationException;
 
+    /** Evaluate the expression using a {@code mapValue} as the source of input variables. */
     Object eval(Map<String, ?> mapValue) throws CelEvaluationException;
+
+    /**
+     * Evaluate a compiled program with {@code mapValue} and late-bound functions {@code
+     * lateBoundFunctionResolver}.
+     */
+    Object eval(Map<String, ?> mapValue, CelFunctionResolver lateBoundFunctionResolver)
+        throws CelEvaluationException;
   }
 }

runtime/src/main/java/dev/cel/runtime/CelRuntime.java

@@ -43,13 +43,11 @@ public interface CelRuntime {
   @Immutable
   abstract class Program implements CelLiteRuntime.Program {
 
-    /** Evaluate the expression without any variables. */
     @Override
     public Object eval() throws CelEvaluationException {
       return evalInternal(Activation.EMPTY);
     }
 
-    /** Evaluate the expression using a {@code mapValue} as the source of input variables. */
     @Override
     public Object eval(Map<String, ?> mapValue) throws CelEvaluationException {
       return evalInternal(Activation.copyOf(mapValue));
@@ -77,10 +75,7 @@ public Object eval(CelVariableResolver resolver, CelFunctionResolver lateBoundFu
           CelEvaluationListener.noOpListener());
     }
 
-    /**
-     * Evaluate a compiled program with {@code mapValue} and late-bound functions {@code
-     * lateBoundFunctionResolver}.
-     */
+    @Override
     public Object eval(Map<String, ?> mapValue, CelFunctionResolver lateBoundFunctionResolver)
         throws CelEvaluationException {
       return evalInternal(

runtime/src/main/java/dev/cel/runtime/DefaultInterpreter.java

@@ -147,6 +147,14 @@ public Object eval(GlobalResolver resolver, CelEvaluationListener listener)
           RuntimeUnknownResolver.fromResolver(resolver), Optional.empty(), listener);
     }
 
+    @Override
+    public Object eval(GlobalResolver resolver, FunctionResolver lateBoundFunctionResolver)
+        throws CelEvaluationException {
+      return eval(resolver,
+          lateBoundFunctionResolver,
+          CelEvaluationListener.noOpListener());
+    }
+
     @Override
     public Object eval(
         GlobalResolver resolver,

runtime/src/main/java/dev/cel/runtime/Interpretable.java

@@ -37,6 +37,17 @@ public interface Interpretable {
   Object eval(GlobalResolver resolver, CelEvaluationListener listener)
       throws CelEvaluationException;
 
+  /**
+   * Runs interpretation with the given activation which supplies name/value bindings.
+   *
+   * <p>This method allows for late-binding functions to be provided per-evaluation, which can be
+   * useful for binding functions which might have side-effects that are not observable to CEL
+   * directly such as recording telemetry or evaluation state in a more granular fashion than a more
+   * general evaluation listener might permit.
+   */
+  Object eval(GlobalResolver resolver, FunctionResolver lateBoundFunctionResolver)
+      throws CelEvaluationException;
+
   /**
    * Runs interpretation with the given activation which supplies name/value bindings.
    *

runtime/src/main/java/dev/cel/runtime/LiteProgramImpl.java

@@ -34,6 +34,16 @@ public Object eval(Map<String, ?> mapValue) throws CelEvaluationException {
     return interpretable().eval(Activation.copyOf(mapValue));
   }
 
+  @Override
+  public Object eval(Map<String, ?> mapValue, CelFunctionResolver lateBoundFunctionResolver)
+      throws CelEvaluationException {
+    return interpretable()
+        .eval(
+            Activation.copyOf(mapValue),
+            lateBoundFunctionResolver,
+            CelEvaluationListener.noOpListener());
+  }
+
   static CelLiteRuntime.Program plan(Interpretable interpretable) {
     return new AutoValue_LiteProgramImpl(interpretable);
   }

runtime/src/test/java/dev/cel/runtime/CelLiteRuntimeTest.java

@@ -41,6 +41,8 @@
 import com.google.testing.junit.testparameterinjector.TestParameterInjector;
 import com.google.testing.junit.testparameterinjector.TestParameters;
 import dev.cel.common.CelAbstractSyntaxTree;
+import dev.cel.common.CelFunctionDecl;
+import dev.cel.common.CelOverloadDecl;
 import dev.cel.common.internal.ProtoTimeUtils;
 import dev.cel.common.types.SimpleType;
 import dev.cel.common.types.StructTypeReference;
@@ -605,4 +607,30 @@ public void nestedMessage_fromImportedProto() throws Exception {
 
     assertThat(result).isEqualTo("foo");
   }
+
+  @Test
+  public void eval_withLateBoundFunction() throws Exception {
+    CelCompiler celCompiler =
+        CelCompilerFactory.standardCelCompilerBuilder()
+            .addFunctionDeclarations(
+                CelFunctionDecl.newFunctionDeclaration(
+                    "lateBoundFunc",
+                    CelOverloadDecl.newGlobalOverload(
+                        "lateBoundFunc_string", SimpleType.STRING, SimpleType.STRING)))
+            .build();
+    CelLiteRuntime celRuntime = CelLiteRuntimeFactory.newLiteRuntimeBuilder().build();
+    CelAbstractSyntaxTree ast = celCompiler.compile("lateBoundFunc('hello')").getAst();
+
+    String result =
+        (String)
+            celRuntime
+                .createProgram(ast)
+                .eval(
+                    ImmutableMap.of(),
+                    CelLateFunctionBindings.from(
+                        CelFunctionBinding.from(
+                            "lateBoundFunc_string", String.class, arg -> arg + " world")));
+
+    assertThat(result).isEqualTo("hello world");
+  }
 }

testing/src/test/resources/protos/BUILD.bazel

@@ -65,7 +65,6 @@ java_lite_proto_cel_library(
 
 java_lite_proto_cel_library_impl(
     name = "multi_file_cel_java_proto",
-    debug = True,
     java_descriptor_class_suffix = "CelDescriptor",
     java_proto_library_dep = ":multi_file_java_proto",
     deps = [