Add a smaller library for string_view so that users can

depend on string_view without depending on all of
//absl/strings:strings

New code that uses string_view.h should depend on
//absl/strings:string_view (Bazel) or
absl::string_view (CMake) instead.
PiperOrigin-RevId: 547283268
Change-Id: I6006b19605ce377d12c462129dda14251d16e1c1

absl/strings/BUILD.bazel

@@ -28,6 +28,20 @@ package(
 licenses(["notice"])
 
 cc_library(
+    name = "string_view",
+    srcs = ["string_view.cc"],
+    hdrs = ["string_view.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:throw_delegate",
+    ],
+)
+
+cc_library(
     name = "strings",
     srcs = [
         "ascii.cc",
@@ -50,7 +64,6 @@ cc_library(
         "str_cat.cc",
         "str_replace.cc",
         "str_split.cc",
-        "string_view.cc",
         "substitute.cc",
     ],
     hdrs = [
@@ -72,8 +85,15 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    textual_hdrs = [
+        # string_view.h was once part of :strings, so string_view.h is
+        # re-exported for backwards compatibility.
+        # New code should directly depend on :string_view.
+        "string_view.h",
+    ],
     deps = [
         ":internal",
+        ":string_view",
         "//absl/base",
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -263,6 +283,7 @@ cc_test(
     tags = ["benchmark"],
     visibility = ["//visibility:private"],
     deps = [
+        ":string_view",
         ":strings",
         "//absl/base:core_headers",
         "//absl/base:raw_logging_internal",
@@ -277,7 +298,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
     deps = [
-        ":strings",
+        ":string_view",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:dynamic_annotations",

absl/strings/CMakeLists.txt

@@ -16,6 +16,23 @@
 
 absl_cc_library(
   NAME
+    string_view
+  HDRS
+    string_view.h
+  SRCS
+    string_view.cc
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::config
+    absl::core_headers
+    absl::throw_delegate
+  PUBLIC
+)
+
+absl_cc_library(
+  NAME
     strings
   HDRS
     "ascii.h"
@@ -30,7 +47,6 @@ absl_cc_library(
     "str_join.h"
     "str_replace.h"
     "str_split.h"
-    "string_view.h"
     "strip.h"
     "substitute.h"
   SRCS
@@ -54,11 +70,11 @@ absl_cc_library(
     "str_cat.cc"
     "str_replace.cc"
     "str_split.cc"
-    "string_view.cc"
     "substitute.cc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
+    absl::string_view
     absl::strings_internal
     absl::base
     absl::bits