Add support for creating a subspan view of a cel::Source.

common/source.cc

@@ -585,6 +585,51 @@ absl::optional<std::pair<int32_t, SourcePosition>> Source::FindLine(
   return std::make_pair(line, line_offsets[static_cast<size_t>(line) - 2]);
 }
 
+SourceSubrange::SourceSubrange(const Source& source, SourceRange range)
+    : source_(source), range_(range) {
+  SourcePosition size = source_.content().size();
+  ABSL_DCHECK(range_.begin >= 0);
+  ABSL_DCHECK(range_.begin <= size);
+  ABSL_DCHECK(range_.end >= range_.begin);
+  ABSL_DCHECK(range_.end <= size);
+  if (range_.begin < 0) {
+    range_.begin = 0;
+  }
+  if (range_.begin > size) {
+    range_.begin = size;
+  }
+  if (range_.end < range_.begin) {
+    range_.end = range_.begin;
+  }
+  if (range_.end > size) {
+    range_.end = size;
+  }
+  for (const auto& line_offset : source_.line_offsets()) {
+    if (line_offset > range_.begin && line_offset <= range_.end) {
+      line_offsets_.push_back(line_offset - range_.begin);
+    }
+  }
+  line_offsets_.push_back(range_.end - range_.begin + 1);
+}
+
+SourceContentView SourceSubrange::content() const {
+  auto parent_content = source_.content();
+  if (parent_content.empty() || range_.begin >= range_.end) {
+    return EmptyContentView();
+  }
+  return absl::visit(
+      [this](auto view) {
+        return SourceContentView(
+            view.subspan(static_cast<size_t>(range_.begin),
+                         static_cast<size_t>(range_.end - range_.begin)));
+      },
+      parent_content.view_);
+}
+
+absl::Span<const SourcePosition> SourceSubrange::line_offsets() const {
+  return absl::MakeConstSpan(line_offsets_);
+}
+
 absl::StatusOr<absl_nonnull SourcePtr> NewSource(absl::string_view content,
                                                  std::string description) {
   return common_internal::NewSourceImpl(std::move(description), content,

common/source.h

@@ -22,6 +22,7 @@
 
 #include "absl/base/attributes.h"
 #include "absl/base/nullability.h"
+#include "absl/container/inlined_vector.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/cord.h"
 #include "absl/strings/string_view.h"
@@ -36,6 +37,7 @@ class SourceImpl;
 }  // namespace common_internal
 
 class Source;
+class SourceSubrange;
 
 // SourcePosition represents an offset in source text.
 using SourcePosition = int32_t;
@@ -94,6 +96,7 @@ class SourceContentView final {
 
  private:
   friend class Source;
+  friend class SourceSubrange;
 
   constexpr SourceContentView() = default;
 
@@ -178,6 +181,7 @@ class Source {
 
  private:
   friend class common_internal::SourceImpl;
+  friend class SourceSubrange;
 
   Source() = default;
 
@@ -187,6 +191,34 @@ class Source {
       SourcePosition position) const;
 };
 
+// `SourceSubrange` is a view of a subrange fo an underlying `Source` object.
+// Intended to be used when the CEL expression is embedded in a larger text
+// representation (such as a.celpolicy).
+//
+// The parent `Source` must outlive this object.
+class SourceSubrange final : public Source {
+ public:
+  SourceSubrange(const Source& source ABSL_ATTRIBUTE_LIFETIME_BOUND,
+                 SourceRange range);
+
+  absl::string_view description() const ABSL_ATTRIBUTE_LIFETIME_BOUND override {
+    return source_.description();
+  }
+
+  // Returns a view of the underlying expression text.
+  ContentView content() const ABSL_ATTRIBUTE_LIFETIME_BOUND override;
+
+  // Returns a `absl::Span` of `SourcePosition` which represent the positions
+  // where new lines occur.
+  absl::Span<const SourcePosition> line_offsets() const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND override;
+
+ private:
+  const Source& source_;
+  SourceRange range_;
+  absl::InlinedVector<SourcePosition, 1> line_offsets_;
+};
+
 using SourcePtr = std::unique_ptr<Source>;
 
 absl::StatusOr<absl_nonnull SourcePtr> NewSource(

common/source_test.cc

@@ -223,5 +223,44 @@ TEST(Source, DisplayErrorLocationFullWidth) {
             "\n | .．＾");
 }
 
+TEST(SourceSubrange, Description) {
+  ASSERT_OK_AND_ASSIGN(auto source, NewSource("hello world", "subrange-test"));
+  SourceSubrange subrange(*source, SourceRange{0, 5});
+  EXPECT_THAT(subrange.description(), Eq("subrange-test"));
+}
+
+TEST(SourceSubrange, Content) {
+  ASSERT_OK_AND_ASSIGN(auto source, NewSource("hello world", "subrange-test"));
+  SourceSubrange subrange(*source, SourceRange{6, 11});
+  EXPECT_THAT(subrange.content().ToString(), Eq("world"));
+}
+
+TEST(SourceSubrange, ContentEmpty) {
+  ASSERT_OK_AND_ASSIGN(auto source, NewSource("hello world", "subrange-test"));
+  SourceSubrange subrange(*source, SourceRange{5, 5});
+  EXPECT_THAT(subrange.content().ToString(), Eq(""));
+}
+
+TEST(SourceSubrange, LineOffsetsNoNewlines) {
+  ASSERT_OK_AND_ASSIGN(auto source,
+                       NewSource("hello\nworld\n", "subrange-test"));
+  SourceSubrange subrange(*source, SourceRange{0, 5});
+  EXPECT_THAT(subrange.line_offsets(), ElementsAre(6));
+}
+
+TEST(SourceSubrange, LineOffsetsWithNewlines) {
+  ASSERT_OK_AND_ASSIGN(auto source,
+                       NewSource("hello\nworld\ncel", "subrange-test"));
+  SourceSubrange subrange(*source, SourceRange{0, 11});
+  EXPECT_THAT(subrange.line_offsets(), ElementsAre(6, 12));
+}
+
+TEST(SourceSubrange, LineOffsetsMiddleSubrange) {
+  ASSERT_OK_AND_ASSIGN(auto source,
+                       NewSource("hello\nworld\ncel\ncpp", "subrange-test"));
+  SourceSubrange subrange(*source, SourceRange{6, 15});
+  EXPECT_THAT(subrange.line_offsets(), ElementsAre(6, 10));
+}
+
 }  // namespace
 }  // namespace cel

compiler/BUILD

@@ -25,6 +25,7 @@ cc_library(
         "//checker:type_checker",
         "//checker:type_checker_builder",
         "//checker:validation_result",
+        "//common:source",
         "//parser:options",
         "//parser:parser_interface",
         "//validator",

compiler/compiler.h

@@ -27,6 +27,7 @@
 #include "checker/type_checker.h"
 #include "checker/type_checker_builder.h"
 #include "checker/validation_result.h"
+#include "common/source.h"
 #include "parser/options.h"
 #include "parser/parser_interface.h"
 #include "validator/validator.h"
@@ -129,9 +130,18 @@ class Compiler {
  public:
   virtual ~Compiler() = default;
 
-  virtual absl::StatusOr<ValidationResult> Compile(
+  absl::StatusOr<ValidationResult> Compile(
+      const Source& source, google::protobuf::Arena* absl_nullable arena) const {
+    return CompileImpl(source, arena);
+  }
+
+  absl::StatusOr<ValidationResult> Compile(const Source& source) const {
+    return CompileImpl(source, nullptr);
+  }
+
+  absl::StatusOr<ValidationResult> Compile(
       absl::string_view source, absl::string_view description,
-      google::protobuf::Arena* absl_nullable arena) const = 0;
+      google::protobuf::Arena* absl_nullable arena) const;
 
   absl::StatusOr<ValidationResult> Compile(absl::string_view source) const {
     return Compile(source, "<input>", nullptr);
@@ -159,8 +169,27 @@ class Compiler {
   // The returned builder does not share state with the compiler and may be
   // modified independently.
   virtual std::unique_ptr<CompilerBuilder> ToBuilder() const = 0;
+
+ protected:
+  virtual absl::StatusOr<ValidationResult> CompileImpl(
+      const Source& source, google::protobuf::Arena* absl_nullable arena) const = 0;
 };
 
+inline absl::StatusOr<ValidationResult> Compiler::Compile(
+    absl::string_view source, absl::string_view description,
+    google::protobuf::Arena* absl_nullable arena) const {
+  absl::StatusOr<SourcePtr> source_obj =
+      NewSource(source, std::string(description));
+  if (!source_obj.ok()) {
+    return source_obj.status();
+  }
+  absl::StatusOr<ValidationResult> result = CompileImpl(**source_obj, arena);
+  if (result.ok()) {
+    result->SetSource(std::move(*source_obj));
+  }
+  return result;
+}
+
 }  // namespace cel
 
 #endif  // THIRD_PARTY_CEL_CPP_COMPILER_COMPILER_INTERFACE_H_

compiler/compiler_factory.cc

@@ -54,14 +54,18 @@ class CompilerImpl : public Compiler {
         validator_(std::move(validator)),
         options_(options) {}
 
-  absl::StatusOr<ValidationResult> Compile(
-      absl::string_view expression, absl::string_view description,
-      google::protobuf::Arena* arena) const override {
-    CEL_ASSIGN_OR_RETURN(auto source,
-                         cel::NewSource(expression, std::string(description)));
+  std::unique_ptr<CompilerBuilder> ToBuilder() const override;
+
+  const TypeChecker& GetTypeChecker() const override { return *type_checker_; }
+  const Parser& GetParser() const override { return *parser_; }
+  const Validator& GetValidator() const override { return validator_; }
+
+ protected:
+  absl::StatusOr<ValidationResult> CompileImpl(
+      const Source& source, google::protobuf::Arena* arena) const override {
     std::vector<cel::ParseIssue> parse_issues;
     absl::StatusOr<std::unique_ptr<cel::Ast>> ast =
-        parser_->Parse(*source, &parse_issues);
+        parser_->Parse(source, &parse_issues);
     if (!ast.ok()) {
       if (!options_.adapt_parser_errors ||
           ast.status().code() != absl::StatusCode::kInvalidArgument ||
@@ -74,26 +78,17 @@ class CompilerImpl : public Compiler {
         check_issues.push_back(TypeCheckIssue::CreateError(
             issue.location(), std::string(issue.message())));
       }
-      ValidationResult result(std::move(check_issues));
-      result.SetSource(std::move(source));
-      return result;
+      return ValidationResult(std::move(check_issues));
     }
     CEL_ASSIGN_OR_RETURN(ValidationResult result,
                          type_checker_->Check(*std::move(ast), arena));
 
-    result.SetSource(std::move(source));
     if (!validator_.validations().empty()) {
       validator_.UpdateValidationResult(result);
     }
     return result;
   }
 
-  std::unique_ptr<CompilerBuilder> ToBuilder() const override;
-
-  const TypeChecker& GetTypeChecker() const override { return *type_checker_; }
-  const Parser& GetParser() const override { return *parser_; }
-  const Validator& GetValidator() const override { return validator_; }
-
  private:
   std::unique_ptr<TypeChecker> type_checker_;
   std::unique_ptr<Parser> parser_;

compiler/compiler_factory_test.cc

@@ -427,5 +427,19 @@ TEST(CompilerFactoryTest, ReturnsIssuesFromParser) {
   EXPECT_THAT(result.GetIssues(), testing::Not(testing::IsEmpty()));
 }
 
+TEST(CompilerFactoryTest, CompileSourceOverload) {
+  ASSERT_OK_AND_ASSIGN(
+      auto builder,
+      NewCompilerBuilder(cel::internal::GetSharedTestingDescriptorPool()));
+
+  ASSERT_THAT(builder->AddLibrary(StandardCompilerLibrary()), IsOk());
+  ASSERT_OK_AND_ASSIGN(auto compiler, builder->Build());
+
+  ASSERT_OK_AND_ASSIGN(auto source, cel::NewSource("1 + 2"));
+  ASSERT_OK_AND_ASSIGN(ValidationResult result, compiler->Compile(*source));
+
+  EXPECT_TRUE(result.IsValid());
+}
+
 }  // namespace
 }  // namespace cel