Fix: allow removing $-prefixed attachments (#114)

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Fix removing attachments with numeric keys, [PR-113](https://github.com/reductstore/reduct-cpp/pull/113)
+- Fix removing entry attachments whose keys start with `$`, #114
 
 ## 1.18.0 - 2026-02-04
 

src/reduct/bucket.cc

@@ -251,15 +251,23 @@ class Bucket : public IBucket {
                           const std::set<std::string>& attachment_keys) const noexcept override {
     QueryOptions options;
     if (!attachment_keys.empty()) {
+      const auto escape_attachment_key = [](const std::string& key) {
+        if (!key.empty() && key.front() == '$') {
+          return fmt::format("${}", key);
+        }
+        return key;
+      };
+
       nlohmann::json when;
       when["$in"] = nlohmann::json::array();
       when["$in"].push_back({{"&key", {{"$cast", "string"}}}});
       for (const auto& key : attachment_keys) {
-        when["$in"].push_back(key);
+        when["$in"].push_back(escape_attachment_key(key));
       }
       options.when = when.dump();
     }
 
+
     Batch remove_batch;
     const auto meta_entry = fmt::format("{}/$meta", entry_name);
     auto query_err = QueryV2({meta_entry}, std::nullopt, std::nullopt, std::move(options),

tests/reduct/entry_api_test.cc

@@ -782,6 +782,27 @@ TEST_CASE("reduct::IBucket should remove entry attachments with numeric keys", "
   REQUIRE(stored_after.empty());
 }
 
+TEST_CASE("reduct::IBucket should remove entry attachments with reserved keys", "[entry_api][1_19]") {
+  Fixture ctx;
+  auto [bucket, _] = ctx.client->CreateBucket(kBucketName);
+  REQUIRE(bucket);
+
+  IBucket::AttachmentMap attachments{
+      {"meta-1", R"({"value":1})"},
+      {"$system", R"({"value":"test"})"},
+      {"meta-2", R"({"value":2})"},
+  };
+
+  REQUIRE(bucket->WriteAttachments("entry-1", attachments) == Error::kOk);
+  REQUIRE(bucket->RemoveAttachments("entry-1", std::set<std::string>{"meta-1", "$system"}) == Error::kOk);
+
+  auto [stored, err] = bucket->ReadAttachments("entry-1");
+  REQUIRE(err == Error::kOk);
+  REQUIRE(stored.size() == 1);
+  REQUIRE(stored.contains("meta-2"));
+  REQUIRE(nlohmann::json::parse(stored.at("meta-2")) == nlohmann::json::parse(attachments.at("meta-2")));
+}
+
 TEST_CASE("Batch should slice data", "[batch]") {
   auto batch = IBucket::Batch();