fix: six bugs found while auditing the library

[Halvanhelv]

Each of these was reproduced against the real library before being fixed, and each has a regression test. Version bumped to 2.1.0 — all are fixes, but DeepLDiff::Request::Error is a new public constant.

1. The options hash was consumed, not read

request.rb:27,31 called Hash#delete on the caller's hash.

opts = { from: :en, to: :ru }
DeepLDiff.translate("hello", opts)  # => "HELLO"
opts                                 # => {} ← emptied
DeepLDiff.translate("hello", opts)  # NoMethodError: undefined method 'detected_source_language'

A frozen hash — which is what a hash of settings kept in a constant is — raised FrozenError on the very first call. The request copies the hash in its initializer now.

2. The chunker measured three different things against one limit

line	measured
next_chunk?	CGI.escape(value).size — escaped
update_chunk	value.size — raw, accumulated
validate_value_size	value.size — raw

So the escaped size of the incoming value was added to a running total of raw sizes. CGI.escape inflates Cyrillic sixfold:

Chunker.new(["яяяяя"] * 4, limit: 50).call
# before → one chunk, 120 escaped — 2.4× over the limit
# after  → four chunks, 30 escaped each

Chunker.new(["я" * 40], limit: 50).call
# before → accepted, 240 escaped
# after  → Error: Too long part 240 > 50

Chunking is the only guard against DeepL's request-size limit, and it did not work for any non-Latin text. Everything is measured escaped now — that is what goes over the wire.

3. A detected source language never matched the target

detect_language returns a String; :to is usually a Symbol. from == to could not fire:

DeepLDiff.translate("привет", { to: :ru })
# before → paid for and translated into its own language
# after  → returned unchanged, only the detection call is made

Compared case-insensitively as strings now. The cache key is deliberately left alone so existing cached entries stay valid.

4. A short API response surfaced two layers away

updates.shift returned nil, which reached Spacing.restore as NoMethodError: undefined method 'strip' for nil. Now:

DeepLDiff::Request::Error: API returned 1 translations for 2 values

Raised at the call site, before a nil can be written to the cache.

5. Non-string scalars crashed

nil  → NoMethodError: undefined method 'empty?' for nil
42   → NoMethodError: undefined method 'empty?' for an instance of Integer
:sym → TypeError: no implicit conversion of Symbol into String

The emptiness check no longer assumes a String, the tokenizer ignores non-strings, and such values pass through untouched. nil keeps collapsing to "" inside a structure, exactly as before — that behavior is covered by an existing test and stays.

6. The count limit was off by one

tail.texts.size > count_limit was tested after the value was added, so a chunk held count_limit + 1 texts:

Chunker.new(%w[a] * 10, count_limit: 3).call
# before → [4, 4, 2]
# after  → [3, 3, 3, 1]

The existing test had the off-by-one baked into its expectation; it is corrected here.

Test plan

• bundle exec rake test — 46 runs, 75 assertions, 0 failures, on Ruby 4.0.5 and 3.2.4 (was 34 runs).
• bundle exec rubocop — no offenses.
• Every one of the six original reproductions was re-run against the fixed library and now behaves correctly.
• Coverage 97.57% → 97.97% (338/345).

https://claude.ai/code/session_01Pda49PcgziFVnibkKKjXRE