fix(mineru): honor dataset language in figure prompts (#18188)

### Summary

Closes #17885.

MinerU figure enrichment now passes the resolved dataset language to
`vision_llm_figure_describe_prompt`. Missing and empty language values
use `English`, matching the other figure-description paths.

This change is limited to MinerU. PR #18021 already fixed the Mistral
path.

test/unit_test/deepdoc/parser/test_mineru_parser.py

@@ -4,8 +4,11 @@ import sys
 from io import BytesIO
 from pathlib import Path
 from types import ModuleType
+from unittest.mock import Mock
 import json
 
+import pytest
+
 
 def _load_mineru_parser(monkeypatch):
     repo_root = Path(__file__).resolve().parents[4]
@@ -39,6 +42,73 @@ def _load_mineru_parser(monkeypatch):
     return module
 
 
+@pytest.mark.p1
+@pytest.mark.parametrize(
+    ("language", "expected_language"),
+    [
+        ("Japanese", "Japanese"),
+        ("", "English"),
+        (None, "English"),
+    ],
+)
+def test_enhance_images_with_vlm_passes_dataset_language_to_prompt(monkeypatch, tmp_path, language, expected_language):
+    module = _load_mineru_parser(monkeypatch)
+    parser = module.MinerUParser()
+    image_path = tmp_path / "figure.png"
+    module.Image.new("RGB", (1, 1)).save(image_path)
+
+    picture_module = ModuleType("rag.app.picture")
+    picture_module.vision_llm_chunk = Mock(return_value="description")
+    prompt = Mock(return_value="prompt")
+    generator_module = ModuleType("rag.prompts.generator")
+    generator_module.vision_llm_figure_describe_prompt = prompt
+    monkeypatch.setitem(sys.modules, "rag.app.picture", picture_module)
+    monkeypatch.setitem(sys.modules, "rag.prompts.generator", generator_module)
+
+    outputs = [{"type": module.MinerUContentType.IMAGE, "img_path": str(image_path)}]
+    parser._enhance_images_with_vlm(outputs, vision_model=object(), language=language)
+
+    prompt.assert_called_once_with(language=expected_language)
+    assert outputs[0]["vlm_description"] == "description"
+
+
+@pytest.mark.p1
+@pytest.mark.parametrize(
+    ("language", "expected_language"),
+    [
+        ("Japanese", "Japanese"),
+        ("", "English"),
+        (None, "English"),
+    ],
+)
+def test_parse_pdf_forwards_normalized_dataset_language_to_image_enhancement(monkeypatch, tmp_path, language, expected_language):
+    module = _load_mineru_parser(monkeypatch)
+    parser = module.MinerUParser()
+    pdf_path = tmp_path / "document.pdf"
+    pdf_path.write_bytes(b"%PDF-1.4 fake")
+    output_dir = tmp_path / "output"
+    vision_model = object()
+
+    monkeypatch.setattr(module, "extract_pdf_outlines", Mock(return_value=[]))
+    monkeypatch.setattr(parser, "__images__", Mock())
+    monkeypatch.setattr(parser, "_run_mineru", Mock(return_value=output_dir))
+    monkeypatch.setattr(parser, "_read_output", Mock(return_value=[]))
+    enhance = Mock()
+    monkeypatch.setattr(parser, "_enhance_images_with_vlm", enhance)
+
+    language_kwargs = {} if language is None else {"lang": language}
+    parser.parse_pdf(
+        filepath=pdf_path,
+        binary=None,
+        output_dir=str(output_dir),
+        delete_output=False,
+        vision_model=vision_model,
+        **language_kwargs,
+    )
+
+    enhance.assert_called_once_with([], vision_model, callback=None, language=expected_language)
+
+
 def test_sanitize_section_text_removes_escaped_html_tags(monkeypatch):
     module = _load_mineru_parser(monkeypatch)
     text = "<table><tr><td>Alpha</td><td>Beta</td></tr></table>"

test/unit_test/rag/app/test_vision_language_callers.py

@@ -125,3 +125,30 @@ def test_mistral_ocr_forwards_language_to_parser(monkeypatch):
     assert tables == []
     assert returned_parser is parser
     assert parser.parse_pdf.call_args.kwargs["lang"] == "Japanese"
+
+
+@pytest.mark.p1
+def test_mineru_forwards_dataset_language_to_parser(monkeypatch):
+    parser = Mock()
+    parser.parse_pdf.return_value = (["section"], [])
+    ocr_model = Mock(mdl=parser)
+    monkeypatch.setattr(naive, "resolve_model_config", Mock(return_value={"llm_name": "mineru"}))
+    monkeypatch.setattr(naive, "LLMBundle", Mock(return_value=ocr_model))
+
+    sections, tables, returned_parser = naive.by_mineru(
+        "document.pdf",
+        binary=b"pdf",
+        from_page=2,
+        to_page=5,
+        lang="Japanese",
+        callback=lambda *_args, **_kwargs: None,
+        parse_method="raw",
+        mineru_llm_name="mineru",
+        tenant_id="tenant-id",
+        vision_model=object(),
+    )
+
+    assert sections == ["section"]
+    assert tables == []
+    assert returned_parser is parser
+    assert parser.parse_pdf.call_args.kwargs["lang"] == "Japanese"