Cast bytearray to string (#3707)

* Add bytearray to string cast, testcase and rename load_bytes to load_raw

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* New bytearray test case and convert failure to pybind11_fail

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* Fix merge comments

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* Assert early if AsString fails
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Porras Huang <pohuang@jackx-vm-1.nvidia.com>

include/pybind11/cast.h

@@ -380,7 +380,7 @@ struct string_caster {
             return false;
         }
         if (!PyUnicode_Check(load_src.ptr())) {
-            return load_bytes(load_src);
+            return load_raw(load_src);
         }
 
         // For UTF-8 we avoid the need for a temporary `bytes` object by using
@@ -458,26 +458,37 @@ private:
 #endif
     }
 
-    // When loading into a std::string or char*, accept a bytes object as-is (i.e.
+    // When loading into a std::string or char*, accept a bytes/bytearray object as-is (i.e.
     // without any encoding/decoding attempt).  For other C++ char sizes this is a no-op.
     // which supports loading a unicode from a str, doesn't take this path.
     template <typename C = CharT>
-    bool load_bytes(enable_if_t<std::is_same<C, char>::value, handle> src) {
+    bool load_raw(enable_if_t<std::is_same<C, char>::value, handle> src) {
         if (PYBIND11_BYTES_CHECK(src.ptr())) {
             // We were passed raw bytes; accept it into a std::string or char*
             // without any encoding attempt.
             const char *bytes = PYBIND11_BYTES_AS_STRING(src.ptr());
-            if (bytes) {
+            if (!bytes) {
+                pybind11_fail("Unexpected PYBIND11_BYTES_AS_STRING() failure.");
+            }
             value = StringType(bytes, (size_t) PYBIND11_BYTES_SIZE(src.ptr()));
             return true;
         }
+        if (PyByteArray_Check(src.ptr())) {
+            // We were passed a bytearray; accept it into a std::string or char*
+            // without any encoding attempt.
+            const char *bytearray = PyByteArray_AsString(src.ptr());
+            if (!bytearray) {
+                pybind11_fail("Unexpected PyByteArray_AsString() failure.");
+            }
+            value = StringType(bytearray, (size_t) PyByteArray_Size(src.ptr()));
+            return true;
         }
 
         return false;
     }
 
     template <typename C = CharT>
-    bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) {
+    bool load_raw(enable_if_t<!std::is_same<C, char>::value, handle>) {
         return false;
     }
 };

tests/test_builtin_casters.py

@@ -133,6 +133,15 @@ def test_bytes_to_string():
     assert m.string_length("💩".encode()) == 4
 
 
+def test_bytearray_to_string():
+    """Tests the ability to pass bytearray to C++ string-accepting functions"""
+    assert m.string_length(bytearray(b"Hi")) == 2
+    assert m.strlen(bytearray(b"bytearray")) == 9
+    assert m.string_length(bytearray()) == 0
+    assert m.string_length(bytearray("🦜", "utf-8", "strict")) == 4
+    assert m.string_length(bytearray(b"\x80")) == 1
+
+
 @pytest.mark.skipif(not hasattr(m, "has_string_view"), reason="no <string_view>")
 def test_string_view(capture):
     """Tests support for C++17 string_view arguments and return values"""