Split "strings" extension into compiler and runtime libraries to allow its usage in Lite runtime.

extensions/BUILD.bazel

@@ -32,6 +32,23 @@ java_library(
     exports = ["//extensions/src/main/java/dev/cel/extensions:strings"],
 )
 
+java_library(
+    name = "strings_compiler_library",
+    visibility = ["//:internal"],
+    exports = ["//extensions/src/main/java/dev/cel/extensions:strings_compiler_library"],
+)
+
+java_library(
+    name = "strings_runtime_library",
+    visibility = ["//:internal"],
+    exports = ["//extensions/src/main/java/dev/cel/extensions:strings_runtime_library"],
+)
+
+cel_android_library(
+    name = "strings_runtime_library_android",
+    exports = ["//extensions/src/main/java/dev/cel/extensions:strings_runtime_library_android"],
+)
+
 java_library(
     name = "math",
     exports = ["//extensions/src/main/java/dev/cel/extensions:math"],

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

@@ -86,9 +86,41 @@ java_library(
     tags = [
     ],
     deps = [
+        ":extension_library",
+        ":strings_compiler_library",
+        ":strings_runtime_library",
+        "//checker:checker_builder",
+        "//common:cel_function_decl",
+        "//compiler:compiler_builder",
+        "//runtime",
+        "@maven//:com_google_errorprone_error_prone_annotations",
+        "@maven//:com_google_guava_guava",
+    ],
+)
+
+java_library(
+    name = "strings_compiler_library",
+    srcs = ["CelStringCompilerLibrary.java"],
+    tags = [
+    ],
+    deps = [
+        ":extension_library",
         "//checker:checker_builder",
         "//common:cel_function_decl",
         "//common:cel_overload_decl",
+        "//common/types",
+        "//compiler:compiler_builder",
+        "@maven//:com_google_errorprone_error_prone_annotations",
+        "@maven//:com_google_guava_guava",
+    ],
+)
+
+java_library(
+    name = "strings_runtime_library",
+    srcs = ["CelStringRuntimeLibrary.java"],
+    tags = [
+    ],
+    deps = [
         "//common/exceptions:bad_format",
         "//common/exceptions:invalid_argument",
         "//common/internal",
@@ -97,17 +129,40 @@ java_library(
         "//common/types:type_providers",
         "//common/values",
         "//common/values:cel_byte_string",
-        "//compiler:compiler_builder",
-        "//extensions:extension_library",
-        "//runtime",
+        "//runtime:evaluation_exception",
         "//runtime:evaluation_exception_builder",
         "//runtime:function_binding",
+        "//runtime:lite_runtime",
         "//runtime:type_resolver",
         "@maven//:com_google_errorprone_error_prone_annotations",
         "@maven//:com_google_guava_guava",
     ],
 )
 
+cel_android_library(
+    name = "strings_runtime_library_android",
+    srcs = ["CelStringRuntimeLibrary.java"],
+    tags = [
+    ],
+    deps = [
+        "//common/exceptions:bad_format",
+        "//common/exceptions:invalid_argument",
+        "//common/internal:date_time_helpers_android",
+        "//common/internal:internal_android",
+        "//common/types:type_providers_android",
+        "//common/types:types_android",
+        "//common/values:cel_byte_string",
+        "//common/values:values_android",
+        "//runtime:evaluation_exception",
+        "//runtime:evaluation_exception_builder",
+        "//runtime:function_binding_android",
+        "//runtime:lite_runtime_android",
+        "//runtime:type_resolver_android",
+        "@maven//:com_google_errorprone_error_prone_annotations",
+        "@maven_android//:com_google_guava_guava",
+    ],
+)
+
 java_library(
     name = "protos",
     srcs = ["CelProtoExtensions.java"],

extensions/src/main/java/dev/cel/extensions/CelStringCompilerLibrary.java

@@ -0,0 +1,286 @@
+// Copyright 2022 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.extensions;
+
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import com.google.errorprone.annotations.Immutable;
+import dev.cel.checker.CelCheckerBuilder;
+import dev.cel.common.CelFunctionDecl;
+import dev.cel.common.CelOverloadDecl;
+import dev.cel.common.types.ListType;
+import dev.cel.common.types.SimpleType;
+import dev.cel.compiler.CelCompilerLibrary;
+import java.util.Set;
+
+/** Internal implementation of CEL string compile-time extensions. */
+@Immutable
+public final class CelStringCompilerLibrary
+    implements CelCompilerLibrary, CelExtensionLibrary.FeatureSet {
+
+  /** Enumeration of functions for String compile-time extension. */
+  public enum Function {
+    CHAR_AT(
+        CelFunctionDecl.newFunctionDeclaration(
+            "charAt",
+            CelOverloadDecl.newMemberOverload(
+                "string_char_at_int",
+                "Returns the character at the given position. If the position is negative, or"
+                    + " greater than the length of the string, the function will produce an error.",
+                SimpleType.STRING,
+                ImmutableList.of(SimpleType.STRING, SimpleType.INT)))),
+    FORMAT(
+        CelFunctionDecl.newFunctionDeclaration(
+            "format",
+            CelOverloadDecl.newMemberOverload(
+                "string_format",
+                "Formats the string using the provided arguments.",
+                SimpleType.STRING,
+                ImmutableList.of(SimpleType.STRING, ListType.create(SimpleType.DYN))))),
+    INDEX_OF(
+        CelFunctionDecl.newFunctionDeclaration(
+            "indexOf",
+            CelOverloadDecl.newMemberOverload(
+                "string_index_of_string",
+                "Returns the integer index of the first occurrence of the search string. If the"
+                    + " search string is not found the function returns -1.",
+                SimpleType.INT,
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING)),
+            CelOverloadDecl.newMemberOverload(
+                "string_index_of_string_int",
+                "Returns the integer index of the first occurrence of the search string from the"
+                    + " given offset. If the search string is not found the function returns"
+                    + " -1. If the substring is the empty string, the index where the search starts"
+                    + " is returned (zero or custom).",
+                SimpleType.INT,
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING, SimpleType.INT)))),
+    JOIN(
+        CelFunctionDecl.newFunctionDeclaration(
+            "join",
+            CelOverloadDecl.newMemberOverload(
+                "list_join",
+                "Returns a new string where the elements of string list are concatenated.",
+                SimpleType.STRING,
+                ListType.create(SimpleType.STRING)),
+            CelOverloadDecl.newMemberOverload(
+                "list_join_string",
+                "Returns a new string where the elements of string list are concatenated using the"
+                    + " separator.",
+                SimpleType.STRING,
+                ImmutableList.of(ListType.create(SimpleType.STRING), SimpleType.STRING)))),
+    LAST_INDEX_OF(
+        CelFunctionDecl.newFunctionDeclaration(
+            "lastIndexOf",
+            CelOverloadDecl.newMemberOverload(
+                "string_last_index_of_string",
+                "Returns the integer index of the last occurrence of the search string. If the"
+                    + " search string is not found the function returns -1.",
+                SimpleType.INT,
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING)),
+            CelOverloadDecl.newMemberOverload(
+                "string_last_index_of_string_int",
+                "Returns the integer index of the last occurrence of the search string from the"
+                    + " given offset. If the search string is not found the function returns -1. If"
+                    + " the substring is the empty string, the index where the search starts is"
+                    + " returned (string length or custom).",
+                SimpleType.INT,
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING, SimpleType.INT)))),
+    LOWER_ASCII(
+        CelFunctionDecl.newFunctionDeclaration(
+            "lowerAscii",
+            CelOverloadDecl.newMemberOverload(
+                "string_lower_ascii",
+                "Returns a new string where all ASCII characters are lower-cased. This function"
+                    + " does not perform Unicode case-mapping for characters outside the ASCII"
+                    + " range.",
+                SimpleType.STRING,
+                SimpleType.STRING))),
+    QUOTE(
+        CelFunctionDecl.newFunctionDeclaration(
+            "strings.quote",
+            CelOverloadDecl.newGlobalOverload(
+                "strings_quote",
+                "Takes the given string and makes it safe to print (without any formatting"
+                    + " due to escape sequences). If any invalid UTF-8 characters are"
+                    + " encountered, they are replaced with \\uFFFD.",
+                SimpleType.STRING,
+                ImmutableList.of(SimpleType.STRING)))),
+    REPLACE(
+        CelFunctionDecl.newFunctionDeclaration(
+            "replace",
+            CelOverloadDecl.newMemberOverload(
+                "string_replace_string_string",
+                "Returns a new string based on the target, which replaces the occurrences of a"
+                    + " search string with a replacement string if present.",
+                SimpleType.STRING,
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING, SimpleType.STRING)),
+            CelOverloadDecl.newMemberOverload(
+                "string_replace_string_string_int",
+                "Returns a new string based on the target, which replaces the occurrences of a"
+                    + " search string with a replacement string if present. The function accepts a"
+                    + " limit on the number of substring replacements to be made. When the"
+                    + " replacement limit is 0, the result is the original string. When the limit"
+                    + " is a negative number, the function behaves the same as replace all.",
+                SimpleType.STRING,
+                ImmutableList.of(
+                    SimpleType.STRING, SimpleType.STRING, SimpleType.STRING, SimpleType.INT)))),
+    REVERSE(
+        CelFunctionDecl.newFunctionDeclaration(
+            "reverse",
+            CelOverloadDecl.newMemberOverload(
+                "string_reverse",
+                "Returns a new string whose characters are the same as the target string,"
+                    + " only formatted in reverse order.",
+                SimpleType.STRING,
+                SimpleType.STRING))),
+    SPLIT(
+        CelFunctionDecl.newFunctionDeclaration(
+            "split",
+            CelOverloadDecl.newMemberOverload(
+                "string_split_string",
+                "Returns a mutable list of strings split from the input by the given separator.",
+                ListType.create(SimpleType.STRING),
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING)),
+            CelOverloadDecl.newMemberOverload(
+                "string_split_string_int",
+                "Returns a mutable list of strings split from the input by the given separator with"
+                    + " the specified limit on the number of substrings produced by the split.",
+                ListType.create(SimpleType.STRING),
+                ImmutableList.of(SimpleType.STRING, SimpleType.STRING, SimpleType.INT)))),
+    SUBSTRING(
+        CelFunctionDecl.newFunctionDeclaration(
+            "substring",
+            CelOverloadDecl.newMemberOverload(
+                "string_substring_int",
+                "returns a string that is a substring of this string. The substring begins with the"
+                    + " character at the specified index and extends to the end of this string.",
+                SimpleType.STRING,
+                ImmutableList.of(SimpleType.STRING, SimpleType.INT)),
+            CelOverloadDecl.newMemberOverload(
+                "string_substring_int_int",
+                "returns a string that is a substring of this string. The substring begins at the"
+                    + " specified beginIndex and extends to the character at index endIndex - 1."
+                    + " Thus the length of the substring is {@code endIndex-beginIndex}.",
+                SimpleType.STRING,
+                ImmutableList.of(SimpleType.STRING, SimpleType.INT, SimpleType.INT)))),
+    TRIM(
+        CelFunctionDecl.newFunctionDeclaration(
+            "trim",
+            CelOverloadDecl.newMemberOverload(
+                "string_trim",
+                "Returns a new string which removes the leading and trailing whitespace in the"
+                    + " target string. The trim function uses the Unicode definition of whitespace"
+                    + " which does not include the zero-width spaces. ",
+                SimpleType.STRING,
+                SimpleType.STRING))),
+    UPPER_ASCII(
+        CelFunctionDecl.newFunctionDeclaration(
+            "upperAscii",
+            CelOverloadDecl.newMemberOverload(
+                "string_upper_ascii",
+                "Returns a new string where all ASCII characters are upper-cased. This function"
+                    + " does not perform Unicode case-mapping for characters outside the ASCII"
+                    + " range.",
+                SimpleType.STRING,
+                SimpleType.STRING)));
+
+    private final CelFunctionDecl functionDecl;
+
+    public String getFunction() {
+      return functionDecl.name();
+    }
+
+    public CelFunctionDecl getFunctionDecl() {
+      return functionDecl;
+    }
+
+    Function(CelFunctionDecl functionDecl) {
+      this.functionDecl = functionDecl;
+    }
+  }
+
+  private static final class Library implements CelExtensionLibrary<CelStringCompilerLibrary> {
+    private final CelStringCompilerLibrary version0;
+
+    Library() {
+      version0 = new CelStringCompilerLibrary(0, ImmutableSet.copyOf(Function.values()));
+    }
+
+    @Override
+    public String name() {
+      return "strings";
+    }
+
+    @Override
+    public ImmutableSet<CelStringCompilerLibrary> versions() {
+      return ImmutableSet.of(version0);
+    }
+  }
+
+  private static final Library LIBRARY = new Library();
+
+  public static CelExtensionLibrary<CelStringCompilerLibrary> library() {
+    return LIBRARY;
+  }
+
+  /** Returns the latest version of the 'strings' compiler extension. */
+  public static CelStringCompilerLibrary strings() {
+    return library().latest();
+  }
+
+  /** Returns the specified version of the 'strings' compiler extension. */
+  public static CelStringCompilerLibrary strings(int version) {
+    return library().version(version);
+  }
+
+  /** Returns the 'strings' compiler extension with only the specified functions. */
+  public static CelStringCompilerLibrary strings(Function... functions) {
+    return strings(ImmutableSet.copyOf(functions));
+  }
+
+  /** Returns the 'strings' compiler extension with only the specified functions. */
+  public static CelStringCompilerLibrary strings(Set<Function> functions) {
+    return new CelStringCompilerLibrary(functions);
+  }
+
+  private final ImmutableSet<Function> functions;
+  private final int version;
+
+  CelStringCompilerLibrary(Set<Function> functions) {
+    this(-1, functions);
+  }
+
+  private CelStringCompilerLibrary(int version, Set<Function> functions) {
+    this.version = version;
+    this.functions = ImmutableSet.copyOf(functions);
+  }
+
+  @Override
+  public int version() {
+    return version;
+  }
+
+  @Override
+  public ImmutableSet<CelFunctionDecl> functions() {
+    return functions.stream().map(Function::getFunctionDecl).collect(toImmutableSet());
+  }
+
+  @Override
+  public void setCheckerOptions(CelCheckerBuilder checkerBuilder) {
+    functions.forEach(function -> checkerBuilder.addFunctionDeclarations(function.functionDecl));
+  }
+}