redis/redis-rb · error · ArgumentError

wrong number of arguments (expected key/path/value triplets)

Error message

wrong number of arguments (expected key/path/value triplets)

What it means

JSON.MSET writes several key/path/value triplets in one atomic command, and the Ruby wrapper takes them as a flat splat, so the total argument count must be a positive multiple of 3. An empty call, or a trailing partial triplet, raises ArgumentError before any serialization happens (lib/redis/commands/modules/json.rb:162). Note that redis.json_mset(some_array) passes ONE argument (an Array), which is not divisible by 3 and hits the same raise.

Source

Thrown at lib/redis/commands/modules/json.rb:162

      end

      # Set one or more JSON values atomically, one per +key+/+path+/+value+ triplet. Either all
      # of the writes are applied or none are. For a key that does not yet exist the +path+ must
      # be the root ("$").
      #
      # By default each value is a Ruby object serialized with JSON.generate; pass +raw: true+ to
      # send already-encoded JSON strings through untouched.
      #
      # @example
      #   redis.json_mset("doc1", "$", { "a" => 1 }, "doc2", "$", { "b" => 2 })
      #     # => "OK"
      #
      # @param [Array] args a flat list of key, path, value triplets
      # @param [Boolean] raw treat each value as an already-encoded JSON string
      # @return [String] the raw "OK" reply
      # @raise [ArgumentError] unless +args+ is a non-empty list of complete triplets
      def json_mset(*args, raw: false)
        raise ArgumentError, "wrong number of arguments (expected key/path/value triplets)" \
          if args.empty? || !(args.size % 3).zero?

        command = [:"JSON.MSET"]
        args.each_slice(3) do |key, path, value|
          command << key << path << (raw ? value : ::JSON.generate(value))
        end
        send_command(command)
      end

      # Get the values at a single +path+ from one or more +keys+.
      #
      # Returns one element per key, in order, parsed from JSON text into a Ruby object (or nil
      # when the key or path does not exist). Pass +raw: true+ to get the unparsed JSON strings.
      #
      # @example
      #   redis.json_mget("doc1", "doc2", "$.a")
      #     # => [[1], [2]]
      #

View on GitHub (pinned to 2ba9010b91)

Solutions

1. Splat the list: redis.json_mset(*triplets)
2. Validate !triplets.empty? && triplets.size % 3 == 0 before calling
3. When building triplets in a loop, append key, path and value together so a partial triplet cannot be produced

Example fix

// before
redis.json_mset(triplets)
// after
redis.json_mset(*triplets)

def json_mset_bulk(redis, *triplets)
  raise ArgumentError, "expected key/path/value triplets" if triplets.empty? || triplets.size % 3 != 0
  redis.json_mset(*triplets)
end

triplets.is_a?(Array) && !triplets.empty? && (triplets.size % 3).zero?

begin
  redis.json_mset(*triplets)
rescue ArgumentError => e
  raise BatchError, "triplet list malformed: #{e.message}"
end

When it happens

Trigger: redis.json_mset() with no args; redis.json_mset("doc", "$") with only 2 args; a dynamically built list of 7 elements whose last triplet lost its value; redis.json_mset(triplets) where triplets is an Array that was never splatted.

Common situations: Forgetting the splat when the triplets live in an array; looping with each_slice(3) over an odd-length list and pushing a partial tail; refactoring several json_set calls into one batched mset and miscounting arguments.

Related errors

• nx and xx are mutually exclusive
• fpha accepts only: #{JSON_SET_FPHA_TYPES.join(', ')}
• index requires a path
• wrong number of arguments
• collect fields must be :all or a non-empty list

AI-assisted analysis of redis/redis-rb@2ba9010b91 (2026-08-23). Data as JSON: /api/errors/ef7833ab53c1ced6. Report an issue: GitHub.