fix: naive_merge splits oversized sections and counts overlap tokens correctly (#15802)

test/unit_test/rag/test_naive_merge.py

@@ -0,0 +1,229 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+"""Regression tests for ``naive_merge`` / ``naive_merge_with_images``.
+
+Guards against the regression introduced by commit db0f6840d (#11434) where the
+default (non-custom-delimiter) path stopped splitting oversized sections at
+sentence boundaries, and the overlap prefix was not counted toward a chunk's
+token budget.
+"""
+
+import re
+
+import pytest
+
+import rag.nlp as nlp
+from rag.nlp import naive_merge, naive_merge_with_images
+
+DEFAULT_DELIMITER = "\n!?。；！？"
+
+
+@pytest.fixture(autouse=True)
+def word_count_tokens(monkeypatch):
+    """Count tokens as whitespace-delimited words (ignoring ``@@..`` position tags).
+
+    Deterministic and tokenizer-independent so chunk-size assertions are exact.
+    """
+
+    def fake_num_tokens(s):
+        s = re.sub(r"@@[0-9]+\t[^\t\n]*", "", s or "")
+        return len(s.split())
+
+    monkeypatch.setattr(nlp, "num_tokens_from_string", fake_num_tokens)
+    return fake_num_tokens
+
+
+def _tok(s):
+    return len(re.sub(r"@@[0-9]+\t[^\t\n]*", "", s or "").split())
+
+
+def _nonempty(chunks):
+    return [c for c in chunks if c.strip()]
+
+
+# --------------------------------------------------------------------------- #
+# naive_merge — text path
+# --------------------------------------------------------------------------- #
+
+
+@pytest.mark.p2
+def test_oversized_section_is_split_at_sentence_boundaries():
+    # One section far larger than chunk_token_num, sentences separated by '\n'.
+    sentence = " ".join(["word"] * 10)  # 10 tokens
+    section = "\n".join([sentence] * 20)  # 200 tokens, single section
+    assert _tok(section) == 200
+
+    chunks = _nonempty(naive_merge([section], chunk_token_num=50, delimiter=DEFAULT_DELIMITER))
+
+    # Pre-regression behaviour: the section is broken into several chunks
+    # instead of a single oversized one.
+    assert len(chunks) > 1
+    # No chunk should greatly exceed the budget (allow one trailing sentence of slack).
+    assert all(_tok(c) <= 50 + 10 for c in chunks)
+    # Content is preserved.
+    assert "".join(chunks).count("word") == 200
+
+
+@pytest.mark.p2
+def test_small_sections_are_merged_not_oversplit():
+    sentences = ["alpha beta gamma delta" for _ in range(8)]  # 4 tokens each
+    chunks = _nonempty(naive_merge(sentences, chunk_token_num=50, delimiter=DEFAULT_DELIMITER))
+    # All 32 tokens comfortably fit one chunk.
+    assert len(chunks) == 1
+    assert _tok(chunks[0]) == 32
+
+
+@pytest.mark.p2
+def test_default_delimiters_are_honored_without_backticks():
+    # Sentences delimited by '?' and '!' (part of the default set) must split.
+    section = ("q " * 10).strip() + "?" + ("r " * 10).strip() + "!" + ("s " * 10).strip()
+    chunks = _nonempty(naive_merge([section], chunk_token_num=12, delimiter=DEFAULT_DELIMITER))
+    assert len(chunks) >= 2
+
+
+@pytest.mark.p2
+def test_empty_delimiter_falls_back_to_token_size_merge():
+    # token_chunker.py calls naive_merge with delimiter="" as a size-only fallback.
+    sections = [f"sentence number {i} here" for i in range(30)]  # 4 tokens each
+    chunks = _nonempty(naive_merge(sections, chunk_token_num=20, delimiter=""))
+    assert len(chunks) >= 1
+    # Must not crash and must not explode into per-character chunks.
+    assert len(chunks) < len(sections)
+
+
+@pytest.mark.p2
+def test_overlap_prefix_is_counted_in_token_budget():
+    # With overlap, each chunk = overlap-prefix + new content. The fix recomputes
+    # the chunk's token count after prepending the prefix, so chunks stay bounded.
+    # Pre-fix, the prefix tokens were not counted, so the per-chunk budget check
+    # fired late and chunks systematically overshot chunk_token_num.
+    sentences = [" ".join(["w"] * 10) for _ in range(30)]
+    chunks = _nonempty(
+        naive_merge(sentences, chunk_token_num=50, delimiter=DEFAULT_DELIMITER, overlapped_percent=20)
+    )
+    assert len(chunks) > 1
+    # Each 10-token sentence divides chunk_token_num evenly, so a correct
+    # accounting yields chunks of exactly the budget. The buggy version
+    # overshot (observed up to 63). A small tolerance guards tokenizer rounding.
+    assert all(_tok(c) <= 50 + 2 for c in chunks)
+
+
+# --------------------------------------------------------------------------- #
+# Custom-delimiter path (intended #11434 behaviour must be preserved)
+# --------------------------------------------------------------------------- #
+
+
+@pytest.mark.p2
+def test_custom_delimiter_ignores_chunk_size():
+    text = "partA##partB##partC"
+    # Backtick-wrapped custom delimiter -> every segment is its own chunk,
+    # regardless of chunk_token_num.
+    chunks = [c.strip() for c in naive_merge([text], chunk_token_num=1000, delimiter="\n。`##`")]
+    assert chunks == ["partA", "partB", "partC"]
+
+
+@pytest.mark.p2
+def test_custom_delimiter_does_not_size_merge():
+    parts = [f"seg{i}" for i in range(5)]
+    text = "##".join(parts)
+    chunks = [c.strip() for c in naive_merge([text], chunk_token_num=1000, delimiter="`##`")]
+    assert chunks == parts
+
+
+# --------------------------------------------------------------------------- #
+# naive_merge_with_images — image path
+# --------------------------------------------------------------------------- #
+
+
+@pytest.mark.p2
+def test_images_oversized_section_is_split():
+    sentence = " ".join(["word"] * 10)
+    section = "\n".join([sentence] * 20)  # 200 tokens
+    texts = [(section, "")]
+    images = [None]
+
+    chunks, imgs = naive_merge_with_images(
+        texts, images, chunk_token_num=50, delimiter=DEFAULT_DELIMITER
+    )
+    nonempty = _nonempty(chunks)
+    assert len(nonempty) > 1
+    # Returned lists stay aligned.
+    assert len(chunks) == len(imgs)
+    assert all(_tok(c) <= 50 + 10 for c in nonempty)
+
+
+@pytest.mark.p2
+def test_images_custom_delimiter_preserved():
+    chunks, imgs = naive_merge_with_images(
+        [("x##y##z", "")], [None], chunk_token_num=1000, delimiter="`##`"
+    )
+    assert [c.strip() for c in chunks] == ["x", "y", "z"]
+    assert len(chunks) == len(imgs)
+
+
+@pytest.mark.p2
+def test_images_plain_string_input():
+    # texts may be plain strings (not tuples).
+    sentence = " ".join(["word"] * 10)
+    section = "\n".join([sentence] * 20)
+    chunks, imgs = naive_merge_with_images(
+        [section], [None], chunk_token_num=50, delimiter=DEFAULT_DELIMITER
+    )
+    assert len(_nonempty(chunks)) > 1
+    assert len(chunks) == len(imgs)
+
+
+@pytest.mark.p2
+def test_images_mismatched_lengths_returns_empty():
+    assert naive_merge_with_images(["a"], [], chunk_token_num=50) == ([], [])
+
+
+@pytest.mark.p2
+def test_images_shared_lazyimage_not_stacked_across_split_sentences():
+    # A single section carries one LazyImage. After splitting into sentences that
+    # merge back into one chunk, the shared image must NOT be duplicated/stacked
+    # (concat_img would otherwise concatenate the blob list with itself).
+    from rag.utils.lazy_image import LazyImage
+
+    image = LazyImage([b"FAKEBLOB"])
+    section = "\n".join([" ".join(["word"] * 10)] * 20)
+
+    _, imgs = naive_merge_with_images(
+        [(section, "")], [image], chunk_token_num=50, delimiter=DEFAULT_DELIMITER
+    )
+    for im in imgs:
+        if isinstance(im, LazyImage):
+            assert len(im._blobs) == 1  # never grows beyond the single source blob
+
+
+@pytest.mark.p2
+def test_images_distinct_lazyimages_are_concatenated():
+    # Two different sections (small enough to land in one chunk) with distinct
+    # images must still be merged together.
+    from rag.utils.lazy_image import LazyImage
+
+    a = LazyImage([b"BLOB_A"])
+    b = LazyImage([b"BLOB_B"])
+    texts = [("alpha beta gamma", ""), ("delta epsilon zeta", "")]
+    _, imgs = naive_merge_with_images(
+        texts, [a, b], chunk_token_num=100, delimiter=DEFAULT_DELIMITER
+    )
+    nonempty_imgs = [im for im in imgs if im is not None]
+    assert len(nonempty_imgs) == 1
+    merged = nonempty_imgs[0]
+    assert isinstance(merged, LazyImage)
+    assert merged._blobs == [b"BLOB_A", b"BLOB_B"]