fix(prosemirror-markdown): stabilize image round-trip — "" ≡ absent on parse (empty-string class)

A stored image authored without `alt` gained a phantom `alt: ""` on every round-trip (`markdownToProseMirror(convertProseMirrorToMarkdown(doc))`): `marked` renders `![](src)` 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 `` 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>
2026-07-04 20:51:34 +03:00
parent 4369bbc53d
commit 2ce672709a
3 changed files with 472 additions and 6 deletions
@@ -635,13 +635,17 @@ const Attachment = Node.create({
      },
      name: {
        default: null,
-        parseHTML: (el: HTMLElement) => el.getAttribute("data-attachment-name"),
+        // Empty-string-vs-absent idempotency (GS-EDIT-REVERT class): "" -> default.
+        parseHTML: (el: HTMLElement) =>
+          el.getAttribute("data-attachment-name") || null,
        renderHTML: (attrs: Record<string, any>) =>
          attrs.name ? { "data-attachment-name": attrs.name } : {},
      },
      mime: {
        default: null,
-        parseHTML: (el: HTMLElement) => el.getAttribute("data-attachment-mime"),
+        // Empty-string-vs-absent idempotency (GS-EDIT-REVERT class): "" -> default.
+        parseHTML: (el: HTMLElement) =>
+          el.getAttribute("data-attachment-mime") || null,
        renderHTML: (attrs: Record<string, any>) =>
          attrs.mime ? { "data-attachment-mime": attrs.mime } : {},
      },
@@ -689,7 +693,10 @@ const Video = Node.create({
      },
      alt: {
        default: null,
-        parseHTML: (el: HTMLElement) => el.getAttribute("aria-label"),
+        // Empty-string-vs-absent idempotency: coerce "" back to the default so a
+        // stray empty `aria-label` never materializes `alt: ""` on a video stored
+        // with no alt (same GS-EDIT-REVERT class as the image `alt` fix).
+        parseHTML: (el: HTMLElement) => el.getAttribute("aria-label") || null,
        renderHTML: (attrs: Record<string, any>) =>
          attrs.alt ? { "aria-label": attrs.alt } : {},
      },
@@ -864,13 +871,15 @@ const diagramAttributes = () => ({
  },
  title: {
    default: null,
-    parseHTML: (el: HTMLElement) => el.getAttribute("data-title"),
+    // Empty-string-vs-absent idempotency (GS-EDIT-REVERT class): "" -> default.
+    parseHTML: (el: HTMLElement) => el.getAttribute("data-title") || null,
    renderHTML: (attrs: Record<string, any>) =>
      attrs.title ? { "data-title": attrs.title } : {},
  },
  alt: {
    default: null,
-    parseHTML: (el: HTMLElement) => el.getAttribute("data-alt"),
+    // Empty-string-vs-absent idempotency (GS-EDIT-REVERT class): "" -> default.
+    parseHTML: (el: HTMLElement) => el.getAttribute("data-alt") || null,
    renderHTML: (attrs: Record<string, any>) =>
      attrs.alt ? { "data-alt": attrs.alt } : {},
  },
@@ -1106,7 +1115,8 @@ const Pdf = Node.create({
      },
      name: {
        default: null,
-        parseHTML: (el: HTMLElement) => el.getAttribute("data-name"),
+        // Empty-string-vs-absent idempotency (GS-EDIT-REVERT class): "" -> default.
+        parseHTML: (el: HTMLElement) => el.getAttribute("data-name") || null,
        renderHTML: (attrs: Record<string, any>) =>
          attrs.name ? { "data-name": attrs.name } : {},
      },
@@ -1491,6 +1501,29 @@ export const docmostExtensions = [
          ...parent.height,
          parseHTML: (el: HTMLElement) => el.getAttribute("height"),
        },
+        // Empty-string-vs-absent idempotency (GS-EDIT-REVERT class). `marked`
+        // renders `![](src)` as `<img alt="">`, so the stock Image `alt`
+        // parseHTML (`getAttribute("alt")`) materializes `alt: ""` on an image
+        // that was stored with NO alt (attr absent). That is a false diff against
+        // the editor-stored form (a no-alt image has alt ABSENT, not ""), so a
+        // git-sync / ai-chat touch of a page with a plain image produced phantom
+        // churn. Coerce an empty string back to the attr's default (null) so the
+        // import is idempotent. A real alt survives verbatim (`|| undefined` keeps
+        // the truthy value; the default fills the empty case). `title` is coerced
+        // the same way for the whole class, even though `marked` does not
+        // currently emit `title=""` — defence in depth against any path that does.
+        // NOTE: this DIVERGES from editor-ext's literal image `alt` parseHTML
+        // (`getAttribute("alt")`, which returns "" verbatim), but CONVERGES on
+        // editor-ext's real STORED shape: an editor image inserted without alt
+        // renders with no `alt` attribute and re-parses as absent, never "".
+        alt: {
+          ...parent.alt,
+          parseHTML: (el: HTMLElement) => el.getAttribute("alt") || null,
+        },
+        title: {
+          ...parent.title,
+          parseHTML: (el: HTMLElement) => el.getAttribute("title") || null,
+        },
      };
    },
  }).configure({ inline: false }),
@@ -0,0 +1,305 @@
+/**
+ * Reusable round-trip-STABILITY matrix helper (fixtures-first).
+ *
+ * A single stored node authored WITHOUT a given string attribute (attr
+ * absent / undefined) must not gain a phantom EMPTY-STRING value after a
+ * markdown round-trip — the "empty-string-vs-absent" churn class. This helper,
+ * given a node spec, drives a matrix of attribute combinations through the REAL
+ * converter (`convertProseMirrorToMarkdown` -> `markdownToProseMirror`) and
+ * asserts byte-stability on two contours:
+ *
+ *   1. RAW round-trip: for the node under test, every attribute the round-trip
+ *      materializes must equal what the INPUT authored — an authored attr keeps
+ *      its value, an ABSENT attr may only reappear at its SCHEMA DEFAULT. If an
+ *      absent attr comes back as a NON-default value (e.g. `alt: ""` where the
+ *      default is `null`), that is an instability and is reported precisely as
+ *      `type.attr: absent -> "<got>"`. This is the contour git-sync / stored
+ *      JSON diffs on, so masking it only in `canonicalize` would leave the noise.
+ *
+ *   2. CANONICAL round-trip: `canonicalizeContent(original)` must deep-equal
+ *      `canonicalizeContent(roundtrip)` (a second, semantic contour).
+ *
+ * The ONLY normalization the helper treats as allowed (not an instability) is
+ * the DOCUMENTED numeric width/height/size/aspectRatio -> string coercion the
+ * converter performs on purpose (a stored numeric `640` re-parses via
+ * `getAttribute` as the string `"640"`). It is encoded here as an explicit
+ * per-spec `numericStringAttrs` set applied to BOTH contours, NOT a silent skip.
+ *
+ * The helper is node-type agnostic: image and the whole media family share the
+ * `align !== "center"` predicate + `<!--name {…}-->` comment machinery, so one
+ * matrix guards the shared class.
+ */
+import { getSchema } from "@tiptap/core";
+import {
+  convertProseMirrorToMarkdown,
+  markdownToProseMirror,
+  canonicalizeContent,
+  docmostExtensions,
+} from "../src/lib/index.js";
+import { firstDivergence } from "./roundtrip-helpers.js";
+
+/** One attribute's two probe values. */
+export interface AttrMatrixEntry {
+  /** Attribute name on the node. */
+  attr: string;
+  /**
+   * The "default" pick. `undefined` means the attribute is OMITTED entirely
+   * (the absent case — the one that can materialize an empty string on import).
+   * A concrete value is authored verbatim.
+   */
+  default: unknown;
+  /** A representative NON-default value to exercise (must survive verbatim). */
+  nonDefault: unknown;
+}
+
+/** A node type + the attribute matrix to sweep for it. */
+export interface NodeStabilitySpec {
+  /** Node type (e.g. "image", "video"). */
+  type: string;
+  /** Attributes always present on the node (e.g. `{ src: "/i.png" }`). */
+  baseAttrs?: Record<string, unknown>;
+  /** Attributes to sweep at default and non-default. */
+  attrMatrix: AttrMatrixEntry[];
+  /**
+   * Attributes whose numeric -> string coercion on round-trip is DOCUMENTED and
+   * intentional; compared modulo `String(x)` on both sides. Defaults to the
+   * converter's known sizing set.
+   */
+  numericStringAttrs?: string[];
+}
+
+/** A single unstable finding, legible enough to tie a gate-lock to. */
+export interface Instability {
+  type: string;
+  attr: string;
+  /** What the input authored: the literal value, or the ABSENT sentinel. */
+  authored: unknown | typeof ABSENT;
+  /** What the round-trip produced. */
+  got: unknown;
+  /** What a stable round-trip should have produced (authored value or default). */
+  expected: unknown;
+}
+
+/** One matrix cell's result. */
+export interface ComboResult {
+  label: string;
+  authored: Record<string, unknown>;
+  /** RAW-contour instabilities on the node under test. */
+  raw: Instability[];
+  /** CANONICAL-contour divergence (path + values) or null when equal. */
+  canonical: { path: string; a: unknown; b: unknown } | null;
+  /** True when the node type failed to round-trip at all (structural loss). */
+  missing: boolean;
+  md: string;
+}
+
+/** Whole-matrix report for one node spec. */
+export interface MatrixReport {
+  type: string;
+  combos: ComboResult[];
+}
+
+/** Sentinel marking an attribute the input did NOT author. */
+export const ABSENT = Symbol("ABSENT");
+
+const DEFAULT_NUMERIC_STRING_ATTRS = [
+  "width",
+  "height",
+  "size",
+  "aspectRatio",
+];
+
+// The ProseMirror schema the converter targets — its attribute `default`s are
+// the authoritative "what an absent attr should re-materialize as" oracle.
+const schema = getSchema(docmostExtensions);
+
+/** Read the schema default for every attribute of a node type. */
+function schemaDefaults(type: string): Record<string, unknown> {
+  const specAttrs = (schema.nodes[type]?.spec?.attrs ?? {}) as Record<
+    string,
+    { default: unknown }
+  >;
+  const out: Record<string, unknown> = {};
+  for (const [k, v] of Object.entries(specAttrs)) out[k] = v.default;
+  return out;
+}
+
+/** Find the first node of a given type anywhere in a PM doc tree. */
+function findFirst(node: any, type: string): any {
+  if (node && node.type === type) return node;
+  for (const child of node?.content ?? []) {
+    const hit = findFirst(child, type);
+    if (hit) return hit;
+  }
+  return null;
+}
+
+/** Coerce a scalar for the documented numeric->string comparison. */
+const numStr = (x: unknown): unknown => (x == null ? x : String(x));
+
+/**
+ * Enumerate the cartesian product of the matrix: every attribute independently
+ * at its default (index 0) or non-default (index 1) pick. The all-default
+ * corner is included (the baseline). Small by construction (2^N over a handful
+ * of at-risk string attrs).
+ */
+function enumerateCombos(matrix: AttrMatrixEntry[]): number[][] {
+  let combos: number[][] = [[]];
+  for (let i = 0; i < matrix.length; i++) {
+    const next: number[][] = [];
+    for (const c of combos) {
+      next.push([...c, 0]);
+      next.push([...c, 1]);
+    }
+    combos = next;
+  }
+  return combos;
+}
+
+/** Build the authored attrs for one combo pick vector. */
+function authoredAttrs(
+  spec: NodeStabilitySpec,
+  picks: number[],
+): Record<string, unknown> {
+  const attrs: Record<string, unknown> = { ...(spec.baseAttrs ?? {}) };
+  spec.attrMatrix.forEach((entry, i) => {
+    if (picks[i] === 1) {
+      attrs[entry.attr] = entry.nonDefault;
+    } else if (entry.default !== undefined) {
+      attrs[entry.attr] = entry.default;
+    }
+    // default === undefined -> OMIT the attr entirely (the absent case).
+  });
+  return attrs;
+}
+
+/** Human-readable label for a combo (which attrs are at non-default). */
+function comboLabel(spec: NodeStabilitySpec, picks: number[]): string {
+  const on = spec.attrMatrix
+    .filter((_, i) => picks[i] === 1)
+    .map((e) => e.attr);
+  return on.length === 0 ? "<all-default>" : on.join("+");
+}
+
+/**
+ * Run the full stability matrix for one node spec and return a structured
+ * report (does NOT throw — the caller asserts, so a failure can print the whole
+ * report). Every combo runs the real export->import pipeline once.
+ */
+export async function runStabilityMatrix(
+  spec: NodeStabilitySpec,
+): Promise<MatrixReport> {
+  const numericStringAttrs = new Set(
+    spec.numericStringAttrs ?? DEFAULT_NUMERIC_STRING_ATTRS,
+  );
+  const defaults = schemaDefaults(spec.type);
+  const combos: ComboResult[] = [];
+
+  for (const picks of enumerateCombos(spec.attrMatrix)) {
+    const authored = authoredAttrs(spec, picks);
+    const doc = { type: "doc", content: [{ type: spec.type, attrs: authored }] };
+    const md = convertProseMirrorToMarkdown(doc);
+    const rt = await markdownToProseMirror(md);
+    const node = findFirst(rt, spec.type);
+
+    const result: ComboResult = {
+      label: comboLabel(spec, picks),
+      authored,
+      raw: [],
+      canonical: null,
+      missing: node == null,
+      md,
+    };
+
+    if (node != null) {
+      // RAW contour: every materialized attr must equal the authored value, or
+      // (for an absent attr) the schema default — modulo the documented numeric
+      // string coercion.
+      const rtAttrs = (node.attrs ?? {}) as Record<string, unknown>;
+      for (const key of Object.keys(rtAttrs)) {
+        const authoredHas = Object.prototype.hasOwnProperty.call(authored, key);
+        const expected = authoredHas ? authored[key] : defaults[key];
+        let got = rtAttrs[key];
+        let exp = expected;
+        if (numericStringAttrs.has(key)) {
+          got = numStr(got);
+          exp = numStr(exp);
+        }
+        if (firstDivergence(got, exp) !== null) {
+          result.raw.push({
+            type: spec.type,
+            attr: key,
+            authored: authoredHas ? authored[key] : ABSENT,
+            got: rtAttrs[key],
+            expected,
+          });
+        }
+      }
+
+      // CANONICAL contour: canonical forms deep-equal, modulo the same numeric
+      // string coercion (applied to both trees so a documented coercion is not
+      // counted as a divergence).
+      const ca = normalizeNumeric(canonicalizeContent(doc), numericStringAttrs);
+      const cb = normalizeNumeric(canonicalizeContent(rt), numericStringAttrs);
+      result.canonical = firstDivergence(ca, cb);
+    }
+
+    combos.push(result);
+  }
+
+  return { type: spec.type, combos };
+}
+
+/**
+ * Deep-copy a canonical tree, coercing the documented numeric->string attrs to
+ * their string form so an intentional `640 -> "640"` coercion is not reported
+ * as a canonical divergence. Only touches the listed attribute keys.
+ */
+function normalizeNumeric(node: any, attrs: Set<string>): any {
+  if (Array.isArray(node)) return node.map((n) => normalizeNumeric(n, attrs));
+  if (node === null || typeof node !== "object") return node;
+  const out: Record<string, unknown> = {};
+  for (const key of Object.keys(node)) {
+    if (key === "attrs" && node.attrs && typeof node.attrs === "object") {
+      const a: Record<string, unknown> = {};
+      for (const [k, v] of Object.entries(node.attrs)) {
+        a[k] = attrs.has(k) ? numStr(v) : v;
+      }
+      out.attrs = a;
+    } else {
+      out[key] = normalizeNumeric(node[key], attrs);
+    }
+  }
+  return out;
+}
+
+/** Flatten a report to just its unstable combos (for a terse assertion). */
+export function unstableCombos(report: MatrixReport): ComboResult[] {
+  return report.combos.filter(
+    (c) => c.missing || c.raw.length > 0 || c.canonical !== null,
+  );
+}
+
+/** Render a report as a legible multi-line string for a failed assertion. */
+export function formatReport(report: MatrixReport): string {
+  const lines: string[] = [`node "${report.type}":`];
+  for (const c of report.combos) {
+    const flags: string[] = [];
+    if (c.missing) flags.push("DID-NOT-ROUND-TRIP");
+    for (const i of c.raw) {
+      const authored =
+        i.authored === ABSENT ? "absent" : JSON.stringify(i.authored);
+      flags.push(
+        `RAW ${i.type}.${i.attr}: ${authored} -> ${JSON.stringify(i.got)} (expected ${JSON.stringify(i.expected)})`,
+      );
+    }
+    if (c.canonical) {
+      flags.push(
+        `CANON @ ${c.canonical.path}: ${JSON.stringify(c.canonical.a)} vs ${JSON.stringify(c.canonical.b)}`,
+      );
+    }
+    const status = flags.length === 0 ? "stable" : flags.join("; ");
+    lines.push(`  [${c.label}] ${status}`);
+  }
+  return lines.join("\n");
+}
@@ -0,0 +1,128 @@
+import { describe, expect, it } from "vitest";
+import {
+  runStabilityMatrix,
+  unstableCombos,
+  formatReport,
+  type NodeStabilitySpec,
+} from "./roundtrip-stability.helper.js";
+
+// ---------------------------------------------------------------------------
+// Round-trip STABILITY matrix for image + the media family.
+//
+// Guards the "empty-string-vs-absent" churn class (GS-EDIT-REVERT family): a
+// stored node authored WITHOUT a string attr (alt/title/caption/aria-label/...)
+// must not gain a phantom `attr: ""` after `markdownToProseMirror(convert…)`.
+// Each spec sweeps the at-risk string attrs at DEFAULT (absent) and at a real
+// NON-default value; the helper asserts both the RAW round-trip (attrs equal the
+// input's, modulo the documented numeric width/height/size/aspectRatio -> string
+// coercion) and the CANONICAL round-trip (canonical forms deep-equal).
+//
+// The image + media family share the `align !== "center"` predicate and the
+// `<!--name {…}-->` comment machinery, so one matrix guards the shared class.
+// align is NOT part of this class (it round-trips correctly) and is not swept.
+// ---------------------------------------------------------------------------
+
+const SPECS: NodeStabilitySpec[] = [
+  {
+    // Image carries the most at-risk string attrs. `alt` is the one marked
+    // materializes as `<img alt="">` on `![](src)` import (the real bug); title
+    // and caption are covered as the same class. attachmentId is a string attr
+    // that must stay absent when unset (control).
+    type: "image",
+    baseAttrs: { src: "/i.png" },
+    attrMatrix: [
+      { attr: "alt", default: undefined, nonDefault: "a real alt text" },
+      { attr: "title", default: undefined, nonDefault: "a real title" },
+      { attr: "caption", default: undefined, nonDefault: "a real caption" },
+      { attr: "attachmentId", default: undefined, nonDefault: "att-42" },
+    ],
+  },
+  {
+    // Video's `alt` rides the `aria-label` attribute (media aria-label at risk).
+    type: "video",
+    baseAttrs: { src: "/v.mp4" },
+    attrMatrix: [
+      { attr: "alt", default: undefined, nonDefault: "a clip" },
+      { attr: "attachmentId", default: undefined, nonDefault: "att-1" },
+    ],
+  },
+  {
+    // Audio carries no alt/title; attachmentId is its only optional string attr.
+    type: "audio",
+    baseAttrs: { src: "/a.mp3" },
+    attrMatrix: [
+      { attr: "attachmentId", default: undefined, nonDefault: "att-2" },
+    ],
+  },
+  {
+    // pdf: link-form media. `name` (filename) is its at-risk string attr.
+    type: "pdf",
+    baseAttrs: { src: "/d.pdf" },
+    attrMatrix: [
+      { attr: "name", default: undefined, nonDefault: "report.pdf" },
+      { attr: "attachmentId", default: undefined, nonDefault: "att-3" },
+    ],
+  },
+  {
+    // attachment: link-form media (file card). `name` + `mime` string attrs.
+    type: "attachment",
+    baseAttrs: { url: "/f.zip" },
+    attrMatrix: [
+      { attr: "name", default: undefined, nonDefault: "bundle.zip" },
+      { attr: "mime", default: undefined, nonDefault: "application/zip" },
+      { attr: "attachmentId", default: undefined, nonDefault: "att-4" },
+    ],
+  },
+  {
+    // embed: link-form media. `provider` is its at-risk string attr (schema
+    // default ""). embed's numeric width/height defaults (800/600) are a SEPARATE,
+    // documented limitation OUTSIDE the empty-string class: they are not in
+    // canonicalize's KNOWN_DEFAULTS, so an ABSENT width/height re-imports as the
+    // 800/600 default and diverges canonically (see the note in canonicalize.ts).
+    // That is canonicalize-owned and out of scope here, so we author the
+    // dimensions at their defaults (as real editor embeds carry them) to keep this
+    // guard focused on the empty-string/provider class.
+    // provider's schema default is "" (NOT null), so a re-imported "" is the
+    // correct value, not a phantom — it is outside the null-default empty-string
+    // class. We author it at its "" default (the default pick) so the sweep still
+    // asserts a non-default provider ("youtube") round-trips, without tripping the
+    // canonicalize KNOWN_DEFAULTS gap for embed's non-null defaults.
+    type: "embed",
+    baseAttrs: { src: "https://example.com/x", width: 800, height: 600 },
+    attrMatrix: [
+      { attr: "provider", default: "", nonDefault: "youtube" },
+    ],
+  },
+  {
+    // drawio: image-form diagram. `title` + `alt` string attrs (data-title/-alt).
+    type: "drawio",
+    baseAttrs: { src: "blob:drawio" },
+    attrMatrix: [
+      { attr: "title", default: undefined, nonDefault: "flow chart" },
+      { attr: "alt", default: undefined, nonDefault: "an alt" },
+      { attr: "attachmentId", default: undefined, nonDefault: "att-5" },
+    ],
+  },
+  {
+    // excalidraw: image-form diagram, same shared diagramAttributes set.
+    type: "excalidraw",
+    baseAttrs: { src: "blob:excalidraw" },
+    attrMatrix: [
+      { attr: "title", default: undefined, nonDefault: "sketch" },
+      { attr: "alt", default: undefined, nonDefault: "an alt" },
+      { attr: "attachmentId", default: undefined, nonDefault: "att-6" },
+    ],
+  },
+];
+
+describe("round-trip stability matrix (image + media family)", () => {
+  for (const spec of SPECS) {
+    it(`${spec.type}: no attr materializes an empty-string / phantom value`, async () => {
+      const report = await runStabilityMatrix(spec);
+      const unstable = unstableCombos(report);
+      // On failure, print the WHOLE matrix so which (attr, value) combos are
+      // unstable is legible.
+      expect(unstable, `\n${formatReport(report)}\n`).toEqual([]);
+    });
+  }
+});