Make absl::StrSplit iterators valid input iterators. `SplitIterator` stores a copy of its delimiter, so the `const` data members of `ByAnyChar`, `ByLength` and `MaxSplits` made their split iterators not-assignable, unlike those of `ByString` and `ByChar`. Dropping that `const` makes the iterators of all built-in delimiters valid input iterators, without changing behavior. The `SimpleDelimiter` example in the documentation drops its `const` member too, so custom delimiters based on it avoid the same problem. PiperOrigin-RevId: 998612982 Change-Id: I2926cecacc4cfa3569899bc4bac806ad8be585f4

diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 19692b3..5fe9b68 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel

@@ -1170,6 +1170,7 @@
     deps = [
         ":string_view",
         ":strings",
+        "//absl/algorithm:container",
         "//absl/base:core_headers",
         "//absl/base:dynamic_annotations",
         "//absl/container:btree",

diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index 23a32c9..1461d94 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt

@@ -401,6 +401,7 @@
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
+    absl::algorithm_container
     absl::btree
     absl::core_headers
     absl::dynamic_annotations

diff --git a/absl/strings/str_split.h b/absl/strings/str_split.h
index e86b29a..dc32af1 100644
--- a/absl/strings/str_split.h
+++ b/absl/strings/str_split.h

@@ -96,7 +96,7 @@
 // function:
 //
 //   struct SimpleDelimiter {
-//     const char c_;
+//     char c_;
 //     explicit SimpleDelimiter(char c) : c_(c) {}
 //     absl::string_view Find(absl::string_view text, size_t pos) {
 //       auto found = text.find(c_, pos);
@@ -206,7 +206,7 @@
   absl::string_view Find(absl::string_view text, size_t pos) const;
 
  private:
-  const std::string delimiters_;
+  std::string delimiters_;
 };
 
 // ByLength
@@ -237,7 +237,7 @@
   absl::string_view Find(absl::string_view text, size_t pos) const;
 
  private:
-  const ptrdiff_t length_;
+  ptrdiff_t length_;
 };
 
 namespace strings_internal {
@@ -291,7 +291,7 @@
 
  private:
   Delimiter delimiter_;
-  const int limit_;
+  int limit_;
   int count_;
 };
 

diff --git a/absl/strings/str_split_test.cc b/absl/strings/str_split_test.cc
index 8155311..7487e00 100644
--- a/absl/strings/str_split_test.cc
+++ b/absl/strings/str_split_test.cc

@@ -14,6 +14,7 @@
 
 #include "absl/strings/str_split.h"
 
+#include <algorithm>
 #include <array>
 #include <cstddef>
 #include <cstdint>
@@ -32,6 +33,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/algorithm/container.h"
 #include "absl/base/macros.h"
 #include "absl/container/btree_map.h"
 #include "absl/container/btree_set.h"
@@ -1036,6 +1038,36 @@
   EXPECT_FALSE(IsFoundAt("abcd", four_char_delim, 0));
 }
 
+TEST(Split, ByAnyCharWorksWithRepeatedFind) {
+  auto splitter = absl::StrSplit("a,b;a", absl::ByAnyChar(",;"));
+  auto it = absl::c_find(splitter, "a");
+  ASSERT_NE(it, splitter.end());
+  // Search on from the next piece, which assigns the iterator.
+  it = std::find(std::next(it), splitter.end(), "a");
+  ASSERT_NE(it, splitter.end());
+  EXPECT_EQ(std::next(it), splitter.end());
+}
+
+TEST(Split, ByLengthWorksWithRepeatedFind) {
+  auto splitter = absl::StrSplit("aba", absl::ByLength(1));
+  auto it = absl::c_find(splitter, "a");
+  ASSERT_NE(it, splitter.end());
+  // Search on from the next piece, which assigns the iterator.
+  it = std::find(std::next(it), splitter.end(), "a");
+  ASSERT_NE(it, splitter.end());
+  EXPECT_EQ(std::next(it), splitter.end());
+}
+
+TEST(Split, MaxSplitsWorksWithRepeatedFind) {
+  auto splitter = absl::StrSplit("a,a,b,c", absl::MaxSplits(',', 2));
+  auto it = absl::c_find(splitter, "a");
+  ASSERT_NE(it, splitter.end());
+  // Search on from the next piece, which assigns the iterator.
+  it = std::find(std::next(it), splitter.end(), "a");
+  ASSERT_NE(it, splitter.end());
+  EXPECT_EQ(*std::next(it), "b,c");
+}
+
 TEST(Split, WorksWithLargeStrings) {
 #if defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
     defined(ABSL_HAVE_MEMORY_SANITIZER) || defined(ABSL_HAVE_THREAD_SANITIZER)