[packet_interface] Remove PacketBuffer::to_vector()

It allocated a vector for each call, which invites heap churn. Only the
tests used it; they now have a local helper.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

esphome/components/packet_interface/packet_buffer.h

@@ -18,8 +18,8 @@ namespace esphome::packet_interface {
  *
  * WARNING: PacketBuffer holds raw pointers to data. The user must ensure that the data remains valid
  * for the lifetime of the PacketBuffer instance. Storing PacketBuffer instances beyond the scope of the data they
- * reference will lead to dangling pointers and undefined behavior, so if you need to store a PacketBuffer, consider
- * copying the data into a std::vector or similar.
+ * reference will lead to dangling pointers and undefined behavior, so to keep a packet, copy it with copy_to() into a
+ * buffer allocated in setup().
  */
 class PacketBuffer {
  public:
@@ -162,17 +162,6 @@ class PacketBuffer {
     return copied;
   }
 
-  /**
-   * Convert the buffer to a std::vector.
-   */
-  std::vector<uint8_t> to_vector() const {
-    std::vector<uint8_t> result;
-    size_t total_size = this->size();
-    result.resize(total_size);
-    this->copy_to(result.data(), total_size);
-    return result;
-  }
-
  private:
   const uint8_t *pre_buffer_{nullptr};
   size_t pre_length_{0};

tests/components/packet_interface/packet_buffer.cpp

@@ -5,6 +5,13 @@
 
 namespace esphome::packet_interface::testing {
 
+// Copies a packet into a vector, for comparing in tests
+static std::vector<uint8_t> to_vector(const esphome::packet_interface::PacketBuffer &data) {
+  std::vector<uint8_t> result(data.size());
+  data.copy_to(result.data(), result.size());
+  return result;
+}
+
 // Test default constructor
 TEST(PacketBufferTest, DefaultConstructor) {
   PacketBuffer buffer;
@@ -154,19 +161,6 @@ TEST(PacketBufferTest, CopyToComposite) {
   EXPECT_EQ(dest[5], 0x06);
 }
 
-// Test to_vector method
-TEST(PacketBufferTest, ToVector) {
-  uint8_t data[] = {0xAA, 0xBB, 0xCC};
-  PacketBuffer buffer(data, 3);
-
-  std::vector<uint8_t> vec = buffer.to_vector();
-
-  EXPECT_EQ(vec.size(), 3);
-  EXPECT_EQ(vec[0], 0xAA);
-  EXPECT_EQ(vec[1], 0xBB);
-  EXPECT_EQ(vec[2], 0xCC);
-}
-
 // Test copying from an offset past the mid buffer
 TEST(PacketBufferTest, CopyToOffsetPastMid) {
   uint8_t pre[] = {0x01, 0x02};
@@ -221,7 +215,7 @@ TEST(PacketBufferTest, EmptyBuffer) {
   EXPECT_EQ(copied, 0);
   EXPECT_EQ(dest[0], 0xFF);  // Unchanged
 
-  std::vector<uint8_t> vec = buffer.to_vector();
+  std::vector<uint8_t> vec = to_vector(buffer);
   EXPECT_EQ(vec.size(), 0);
 }
 

tests/components/uart/uart_packet_interface.cpp

@@ -9,6 +9,13 @@
 
 namespace esphome::uart::testing {
 
+// Copies a packet into a vector, for comparing in tests
+static std::vector<uint8_t> to_vector(const esphome::packet_interface::PacketBuffer &data) {
+  std::vector<uint8_t> result(data.size());
+  data.copy_to(result.data(), result.size());
+  return result;
+}
+
 using packet_interface::PacketBuffer;
 using packet_interface::PacketMetaData;
 
@@ -26,9 +33,8 @@ class UartPacketInterfaceTest : public ::testing::Test {
     interface_.set_uart_parent(&uart_);
     interface_.setup();
 
-    interface_.add_packet_interface_listener([this](const PacketBuffer &data, const PacketMetaData &meta) {
-      received_packets_.push_back(data.to_vector());
-    });
+    interface_.add_packet_interface_listener(
+        [this](const PacketBuffer &data, const PacketMetaData &meta) { received_packets_.push_back(to_vector(data)); });
   }
 };