fix: (cont.) Remove Extra Space Before and After Group Items using Inline Boundaries

[wanadzhar913]

Details

This is a continuation of the work in Pull Request: #458

which emoves extra space before and after group items to resolve the issue raised in #2745

Resolves #371
Resolves docling-project/docling#2745

Approach

Refactors inline spacing in docling_core/transforms/serializer/common.py into a clearer decision flow centered on _classify_inline_boundary() instead the old approach in #458 where we just remove the space (" ") when joining all parts without separators.

Control Flow

_join_inline_parts() is the entry point. It walks adjacent inline chunks, calls _classify_inline_boundary() for each boundary condition, and inserts a space only when that classifier returns InlineBoundary.SPACE.

_classify_inline_boundary() now handles boundaries in a fixed order:

• Existing whitespace: if either side already carries whitespace, it returns JOIN and avoids adding another space.
• Provenance-based signals: _classify_provenance_boundary() checks original text and provenance/source positions to decide whether the boundary should join or include a space.
• Text-to-text rules: if both sides are TextItems, _classify_text_boundary() applies rules for styled/plain text transitions, punctuation, and short word continuations.
• Code/formula/link separation: _is_semantic_inline_atom() identifies code, formulas, and links so they can be visually separated from regular text when needed.
• Final fallback: _classify_ambiguous_word_boundary() handles uncertain styled/plain word splits by joining likely continuations like Pars + ing, otherwise preferring readability with a space.

Helper Roles

_is_styled_text() detects whether a text item has visible formatting or a hyperlink, which feeds the text-boundary logic. _is_semantic_inline_atom() marks inline items that should usually stand apart from regular text, especially code, formulas, and links.

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[wanadzhar913]

Hi @ceberam, do review when you can. Thanks so much! Happy to just reuse the old approach in #458 where we just remove the space (" ") when joining all parts without separators. Let me know what you prefer.

[github-actions]

✅ DCO Check Passed

Thanks @wanadzhar913, all your commits are properly signed off. 🎉

[PeterStaar-IBM]

lgtm!

[codecov]

Codecov Report

❌ Patch coverage is 96.93878% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
docling_core/transforms/serializer/common.py	96.87%	3 Missing ⚠️

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