Add HomogeneousLiteral Validator

common/navigation/BUILD.bazel

@@ -1,6 +1,6 @@
 package(
     default_applicable_licenses = ["//:license"],
-    default_visibility = ["//visibility:public"],  # TODO: Expose when ready
+    default_visibility = ["//visibility:public"],
 )
 
 java_library(

common/src/main/java/dev/cel/common/CelOptions.java

@@ -301,7 +301,11 @@ public abstract static class Builder {
      * checker will implicitly coerce them to type dyn.
      *
      * <p>This flag is recommended for all new uses of CEL.
+     *
+     * @deprecated Use standalone {@code dev.cel.validators.validator.HomogeneousLiteralValidator}
+     *     instead.
      */
+    @Deprecated
     public abstract Builder enableHomogeneousLiterals(boolean value);
 
     /**

validator/BUILD.bazel

@@ -1,6 +1,6 @@
 package(
     default_applicable_licenses = ["//:license"],
-    default_visibility = ["//visibility:public"],  # TODO: Expose when ready
+    default_visibility = ["//visibility:public"],
 )
 
 java_library(

validator/src/main/java/dev/cel/validator/validators/BUILD.bazel

@@ -47,6 +47,25 @@ java_library(
     ],
 )
 
+java_library(
+    name = "homogeneous_literal",
+    srcs = [
+        "HomogeneousLiteralValidator.java",
+    ],
+    tags = [
+    ],
+    deps = [
+        "//bundle:cel",
+        "//common",
+        "//common/ast",
+        "//common/navigation",
+        "//common/types:cel_types",
+        "//common/types:type_providers",
+        "//validator:ast_validator",
+        "@maven//:com_google_guava_guava",
+    ],
+)
+
 java_library(
     name = "literal_validator",
     srcs = [

validator/src/main/java/dev/cel/validator/validators/HomogeneousLiteralValidator.java

@@ -0,0 +1,147 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package dev.cel.validator.validators;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import dev.cel.bundle.Cel;
+import dev.cel.common.CelAbstractSyntaxTree;
+import dev.cel.common.ast.CelExpr;
+import dev.cel.common.ast.CelExpr.CelCreateMap;
+import dev.cel.common.ast.CelExpr.ExprKind.Kind;
+import dev.cel.common.navigation.CelNavigableAst;
+import dev.cel.common.navigation.CelNavigableExpr;
+import dev.cel.common.types.CelType;
+import dev.cel.common.types.CelTypes;
+import dev.cel.validator.CelAstValidator;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Optional;
+
+/**
+ * HomogeneousLiteralValidator checks that all list and map literals entries have the same types,
+ * i.e. no mixed list element types or mixed map key or map value types.
+ */
+public class HomogeneousLiteralValidator implements CelAstValidator {
+  private final ImmutableSet<String> exemptFunctions;
+
+  /**
+   * Construct a new instance of {@link HomogeneousLiteralValidator}. This validator will not for
+   * functions in {@code exemptFunctions}.
+   */
+  public static HomogeneousLiteralValidator newInstance(Iterable<String> exemptFunctions) {
+    return new HomogeneousLiteralValidator(exemptFunctions);
+  }
+
+  /**
+   * Construct a new instance of {@link HomogeneousLiteralValidator}. This validator will not for
+   * functions in {@code exemptFunctions}.
+   */
+  public static HomogeneousLiteralValidator newInstance(String... exemptFunctions) {
+    return newInstance(Arrays.asList(exemptFunctions));
+  }
+
+  @Override
+  public void validate(CelNavigableAst navigableAst, Cel cel, IssuesFactory issuesFactory) {
+    navigableAst
+        .getRoot()
+        .descendants()
+        .filter(
+            node ->
+                node.getKind().equals(Kind.CREATE_LIST) || node.getKind().equals(Kind.CREATE_MAP))
+        .filter(node -> !isExemptFunction(node))
+        .map(CelNavigableExpr::expr)
+        .forEach(
+            expr -> {
+              if (expr.exprKind().getKind().equals(Kind.CREATE_LIST)) {
+                validateList(navigableAst.getAst(), issuesFactory, expr);
+              } else if (expr.exprKind().getKind().equals(Kind.CREATE_MAP)) {
+                validateMap(navigableAst.getAst(), issuesFactory, expr);
+              }
+            });
+  }
+
+  private void validateList(CelAbstractSyntaxTree ast, IssuesFactory issuesFactory, CelExpr expr) {
+    CelType previousType = null;
+    HashSet<Integer> optionalIndices = new HashSet<>(expr.createList().optionalIndices());
+    ImmutableList<CelExpr> elements = expr.createList().elements();
+    for (int i = 0; i < elements.size(); i++) {
+      CelExpr element = elements.get(i);
+      CelType currentType = ast.getType(element.id()).get();
+      if (optionalIndices.contains(i)) {
+        currentType = currentType.parameters().get(0);
+      }
+
+      if (previousType == null) {
+        previousType = currentType;
+        continue;
+      }
+
+      reportErrorIfUnassignable(issuesFactory, element.id(), previousType, currentType);
+    }
+  }
+
+  private void validateMap(CelAbstractSyntaxTree ast, IssuesFactory issuesFactory, CelExpr expr) {
+    CelType previousKeyType = null;
+    CelType previousValueType = null;
+    for (CelCreateMap.Entry entry : expr.createMap().entries()) {
+      CelType currentKeyType = ast.getType(entry.key().id()).get();
+      CelType currentValueType = ast.getType(entry.value().id()).get();
+      if (entry.optionalEntry()) {
+        currentValueType = currentValueType.parameters().get(0);
+      }
+
+      if (previousKeyType == null) {
+        previousKeyType = currentKeyType;
+        previousValueType = currentValueType;
+        continue;
+      }
+
+      reportErrorIfUnassignable(issuesFactory, entry.id(), previousKeyType, currentKeyType);
+      reportErrorIfUnassignable(issuesFactory, entry.id(), previousValueType, currentValueType);
+    }
+  }
+
+  private void reportErrorIfUnassignable(
+      IssuesFactory issuesFactory, long elementId, CelType previousType, CelType currentType) {
+    if (!previousType.isAssignableFrom(currentType)) {
+      issuesFactory.addError(
+          elementId,
+          String.format(
+              "expected type '%s' but found '%s'",
+              CelTypes.format(previousType), CelTypes.format(currentType)));
+    }
+  }
+
+  private boolean isExemptFunction(CelNavigableExpr listExpr) {
+    Optional<CelNavigableExpr> parent = listExpr.parent();
+    while (parent.isPresent()) {
+      CelNavigableExpr node = parent.get();
+      if (node.getKind().equals(Kind.CALL)) {
+        if (exemptFunctions.contains(node.expr().callOrDefault().function())) {
+          return true;
+        }
+      }
+
+      parent = node.parent();
+    }
+
+    return false;
+  }
+
+  private HomogeneousLiteralValidator(Iterable<String> exemptFunctions) {
+    this.exemptFunctions = ImmutableSet.copyOf(exemptFunctions);
+  }
+}

validator/src/test/java/dev/cel/validator/validators/BUILD.bazel

@@ -13,10 +13,12 @@ java_library(
         "//common:compiler_common",
         "//common:options",
         "//common/types",
+        "//extensions:optional_library",
         "//runtime",
         "//validator",
         "//validator:validator_builder",
         "//validator/validators:duration",
+        "//validator/validators:homogeneous_literal",
         "//validator/validators:regex",
         "//validator/validators:timestamp",
         "@maven//:com_google_guava_guava",