Add a test for write access failures. (#4496)

[SC-35061](https://app.shortcut.com/tiledb-inc/story/35061/add-tests-for-write-access-failures)

See also
#4052 (review).

The test runs on non-Windows only.

---
TYPE: NO_HISTORY

test/src/unit-capi-query.cc

@@ -41,6 +41,7 @@
 #include <test/support/tdb_catch.h>
 #include "test/support/src/helpers.h"
 #include "test/support/src/vfs_helpers.h"
+#include "tiledb/platform/platform.h"
 #ifdef _WIN32
 #include "tiledb/sm/filesystem/win.h"
 #else
@@ -704,3 +705,102 @@ TEST_CASE_METHOD(
   tiledb_array_free(&rarray);
   remove_temp_dir(temp_dir);
 }
+
+TEST_CASE_METHOD(
+    QueryFx,
+    "C API: Test query write failure",
+    "[capi][query][write-failure]") {
+  // DenyWriteAccess is not supported on Windows.
+  if constexpr (tiledb::platform::is_os_windows)
+    return;
+  SupportedFsLocal local_fs;
+  std::string temp_dir = local_fs.temp_dir();
+  std::string array_name = temp_dir + "write_failure";
+  create_temp_dir(temp_dir);
+
+  tiledb_layout_t layout =
+      GENERATE(TILEDB_ROW_MAJOR, TILEDB_UNORDERED, TILEDB_GLOBAL_ORDER);
+  tiledb_array_type_t array_type =
+      layout == TILEDB_UNORDERED ? TILEDB_SPARSE : TILEDB_DENSE;
+
+  tiledb_ctx_t* ctx;
+  int rc;
+  {
+    tiledb_array_schema_t* schema;
+    tiledb_domain_t* domain;
+    tiledb_dimension_t* dim;
+    tiledb_attribute_t* attr;
+
+    rc = tiledb_ctx_alloc(nullptr, &ctx);
+    REQUIRE(rc == TILEDB_OK);
+
+    rc = tiledb_array_schema_alloc(ctx, array_type, &schema);
+    REQUIRE(rc == TILEDB_OK);
+
+    rc = tiledb_domain_alloc(ctx, &domain);
+    REQUIRE(rc == TILEDB_OK);
+
+    int bounds[] = {0, 4};
+    int extent = 1;
+    rc = tiledb_dimension_alloc(ctx, "d1", TILEDB_INT32, bounds, &extent, &dim);
+    REQUIRE(rc == TILEDB_OK);
+    rc = tiledb_domain_add_dimension(ctx, domain, dim);
+    REQUIRE(rc == TILEDB_OK);
+    rc = tiledb_array_schema_set_domain(ctx, schema, domain);
+    REQUIRE(rc == TILEDB_OK);
+
+    rc = tiledb_attribute_alloc(ctx, "attr1", TILEDB_INT32, &attr);
+    REQUIRE(rc == TILEDB_OK);
+    rc = tiledb_array_schema_add_attribute(ctx, schema, attr);
+    REQUIRE(rc == TILEDB_OK);
+
+    rc = tiledb_array_create(ctx, array_name.c_str(), schema);
+    REQUIRE(rc == TILEDB_OK);
+
+    tiledb_attribute_free(&attr);
+    tiledb_dimension_free(&dim);
+    tiledb_domain_free(&domain);
+    tiledb_array_schema_free(&schema);
+  }
+
+  {
+    DenyWriteAccess dwa{array_name + "/__fragments"};
+
+    tiledb_array_t* array;
+    tiledb_query_t* query;
+    rc = tiledb_array_alloc(ctx, array_name.c_str(), &array);
+    REQUIRE(rc == TILEDB_OK);
+    rc = tiledb_array_open(ctx, array, TILEDB_WRITE);
+    REQUIRE(rc == TILEDB_OK);
+
+    rc = tiledb_query_alloc(ctx, array, TILEDB_WRITE, &query);
+    REQUIRE(rc == TILEDB_OK);
+    rc = tiledb_query_set_layout(ctx, query, layout);
+    REQUIRE(rc == TILEDB_OK);
+    int data[] = {0, 1, 2, 3, 4};
+    uint64_t data_size = sizeof(data);
+    rc = tiledb_query_set_data_buffer(ctx, query, "attr1", data, &data_size);
+    REQUIRE(rc == TILEDB_OK);
+    if (array_type == TILEDB_SPARSE) {
+      rc = tiledb_query_set_data_buffer(ctx, query, "d1", data, &data_size);
+      REQUIRE(rc == TILEDB_OK);
+    }
+
+    rc = tiledb_query_submit(ctx, query);
+    REQUIRE(rc != TILEDB_OK);
+
+    tiledb_error_t* err;
+    rc = tiledb_ctx_get_last_error(ctx, &err);
+    REQUIRE(rc == TILEDB_OK);
+    const char* msg;
+    rc = tiledb_error_message(err, &msg);
+    REQUIRE(rc == TILEDB_OK);
+    REQUIRE(
+        std::string(msg).find("Cannot create directory") != std::string::npos);
+
+    tiledb_error_free(&err);
+    tiledb_query_free(&query);
+    tiledb_array_free(&array);
+  }
+  tiledb_ctx_free(&ctx);
+}

test/support/src/vfs_helpers.h

@@ -33,6 +33,7 @@
 #ifndef TILEDB_VFS_HELPERS_H
 #define TILEDB_VFS_HELPERS_H
 
+#include <filesystem>
 #include "test/support/src/helpers.h"
 #include "test/support/tdb_catch.h"
 
@@ -683,6 +684,41 @@ struct TemporaryDirectoryFixture {
   const std::vector<std::unique_ptr<SupportedFs>> supported_filesystems_;
 };
 
+/**
+ * Denies write access to a local filesystem path.
+ *
+ * Not supported on Windows. The permissions function there sets the
+ * readonly bit on the path, which is not supported on directories.
+ *
+ * To support it on Windows we would have to add and remove Access Control
+ * Lists, which is a nontrivial thing to do.
+ */
+class DenyWriteAccess {
+ public:
+  DenyWriteAccess() = delete;
+
+  DenyWriteAccess(const std::string& path)
+      : path_(path)
+      , previous_perms_(std::filesystem::status(path).permissions()) {
+    std::filesystem::permissions(
+        path_,
+        std::filesystem::perms::owner_write,
+        std::filesystem::perm_options::remove);
+  }
+
+  ~DenyWriteAccess() {
+    std::filesystem::permissions(
+        path_, previous_perms_, std::filesystem::perm_options::replace);
+  }
+
+ private:
+  /** The path. */
+  const std::string path_;
+
+  /** The previous permissions of the path. */
+  const std::filesystem::perms previous_perms_;
+};
+
 }  // End of namespace test
 }  // End of namespace tiledb