SegmentOperations write paths: set_String on ITsString.BaselineText (sibling of #170, 8 sites)

[MattGyverLee]

Context

Companion to #170. ISegment.BaselineText is ITsString (confirmed: liblcm/src/SIL.LCModel/InterfaceAdditions.cs:542 declares ITsString BaselineText { get; } — a read-only virtual computed property derived from ((IStTxtPara)Owner).Contents.GetSubstring(BeginOffset, EndOffset) per OverridesCellar.cs:4397).

#170 fixed the read path (GetBaselineText). The write paths in the same file have the same root-cause bug — they call .set_String(ws, mkstr) on an ITsString as if it were IMultiString.

Two problems compound here:

1. ITsString has no .set_String method → AttributeError at runtime
2. Even if it did, BaselineText is a computed, read-only property with no backing store — writes would have nothing to persist to. The backing store is IStTxtPara.Contents; correct edits must rewrite the paragraph's contents with the segment range replaced (or use LCM's ParagraphParser / AnalysisAdjuster services).

Affected sites (flexlibs2/code/TextsWords/SegmentOperations.py)

Line	Method	Pattern
279	SetBaselineText	segment_obj.BaselineText.set_String(ws, mkstr)
523	Create	segment.BaselineText.set_String(ws, mkstr)
688	GetSyncableProperties	GetMultiStringDict(item.BaselineText) — IMultiString helper called on ITsString
887	SplitSegment (first segment)	first_segment.BaselineText.set_String(...)
894	SplitSegment (second segment)	second_segment.BaselineText.set_String(...)
974	MergeSegments (first call)	merged_segment.BaselineText.set_String(...)
987	MergeSegments (second call)	merged_segment.BaselineText.set_String(...)
1359	RebuildSegments	segment.BaselineText.set_String(...)

Source

Domain audit during work on #170 / #171 (2026-05-30). Sweep covered all segment*.BaselineText.set_String and GetMultiStringDict(.*BaselineText) occurrences in the file.

Suggested fix shape (for the eventual cycle)

• Route segment-text edits through IStTxtPara.Contents (e.g., assemble a new ITsString for Contents with the segment range replaced via ITsStrBldr), then trigger LCM's segment re-derivation.
• For GetSyncableProperties: serialize BaselineText as a plain string (no WS dictionary), since it has no WS axis.

[MattGyverLee]

Code Analysis — All set_String sites in SegmentOperations.py

Reviewed flexlibs2/code/TextsWords/SegmentOperations.py.

Why BaselineText.set_String is always a no-op

ISegment.BaselineText is a computed, read-only ITsString derived from IStTxtPara.Contents. It is not an IMultiString. Calling .set_String(ws, tss) on it is silently discarded at the LCM layer — the value is never stored.

FreeTranslation and LiteralTranslation are genuine IMultiString fields; .set_String() is correct for those.

Complete site inventory

#	Line	Method	Field	Status
1	~365	SetFreeTranslation	FreeTranslation.set_String	Correct — IMultiString
2	~440	SetLiteralTranslation	LiteralTranslation.set_String	Correct — IMultiString
3	~540	Create	BaselineText.set_String	Bug — no-op
4	~928	SplitSegment	first_segment.BaselineText.set_String	Bug — no-op
5	~935	SplitSegment	second_segment.BaselineText.set_String	Bug — no-op
6	~1038	MergeSegments	merged_segment.BaselineText.set_String	Bug — no-op
7	~1417	RebuildSegments (loop)	segment.BaselineText.set_String	Bug — no-op (×N)
8	~661	Duplicate	BaselineText.CopyAlternatives	Bug — CopyAlternatives is an IMultiString API; calling it on ITsString raises or silently fails

5 broken executable sites (+ 1 type-mismatch in Duplicate). The remaining 2 are correct.

Reference fix

SetBaselineText (lines 282–290) is already correct — it navigates to segment_obj.Paragraph.Contents, uses TsStrBldr.ReplaceTsString, and assigns back to para.Contents. All 5 broken methods should adopt the same pattern instead of calling .set_String on the segment directly.

These bugs are tightly coupled to the SegmentsOS direct-mutation bugs in #174 — fixing both together in one pass is strongly recommended.

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Generated by Claude Code