Reviewer addition to the round-trip stability matrix: besides "attr absent" and
"attr has a real value", a string attr in the empty-string class has a third,
degenerate state — a LITERAL "" (a user types alt/title/name in the editor then
deletes it, and Tiptap persists `attr: ""`, distinct from never-set). The fix's
`getAttribute(...) || null` coercion normalizes such a stored "" to the default
on the FIRST round-trip (a one-time "" -> null diff) and is byte-stable from the
SECOND round-trip on.
Adds a convergence contract to the reusable matrix helper (emptyStringClass flag
+ runConvergenceCase): pass 1 must converge the attr to its schema default (NOT
asserted byte-stable vs the "" input — that is the intended one-time
normalization); pass 2 must deep-equal pass 1 (idempotent thereafter). Driven for
every empty-string-class attr across image + the media family (image/drawio
alt+title, video alt via aria-label, pdf/attachment name, attachment mime).
Documents the one-time normalization so a future sync/QA diff does not flag the
single "" -> null change as converter corruption.
Gate: package suite 33 files / 682 tests passed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
A stored image authored without `alt` gained a phantom `alt: ""` on every
round-trip (`markdownToProseMirror(convertProseMirrorToMarkdown(doc))`): `marked`
renders `` as `<img alt="">`, and the stock tiptap Image `alt` parseHTML
(`getAttribute("alt")`) materialized the empty string where the original had no
attribute. That false diff is a real GS-EDIT-REVERT churn source — an agent /
git-sync touch of a page with an image mutates the stored JSON (`absent -> ""`),
producing phantom diffs that can overwrite live edits.
Fix is PARSE-SIDE ("" ≡ absent), so the RAW round-trip is idempotent — not only
the canonical form (history / stored JSON diff on the raw shape; masking it only
in canonicalize would leave that noise). `image.alt`/`title` parseHTML now coerce
`getAttribute(...) || null`, plus defense-in-depth `|| null` across the at-risk
empty-string class (video aria-label, drawio/excalidraw title+alt, pdf name,
attachment name+mime) matching the existing `image.caption || null` precedent.
NOTE — image `align` is NOT changed: it round-trips correctly (center via the
schema default "center", left/right via the `<!--img {...}-->` comment). Its
`toBeUndefined()` in the git-sync gate is canonical-form normalization, not a loss.
Intentional divergence from editor-ext: editor-ext's literal `alt` parseHTML
returns "" verbatim, but this coercion CONVERGES on editor-ext's real STORED
shape (an image inserted without alt has no `alt` attribute -> re-parses absent,
never ""), so the round-trip is idempotent and matches real documents.
Adds a reusable, node-agnostic round-trip-stability matrix helper
(test/roundtrip-stability.helper.ts) — given a node + attr spec it enumerates
default/non-default combos and asserts byte-stability of BOTH the raw and the
canonical round-trip (the documented numeric width/height→string coercion encoded
as an explicit allowed normalization) — driven over image + the whole media
family (video/audio/pdf/attachment/embed/drawio/excalidraw). The only raw
empty-string instability it found was image.alt; the family was already stable.
Gate: package suite 33 files / 672 tests passed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
agent_coder