fix(pptx): emit a structurally valid package on serialize (#92)

Three serializeDeck bugs corrupted the generated .pptx (missing parts /
invalid image bytes) even from clean source templates, triggering a
PowerPoint repair prompt and rejection by stricter consumers (Google
Slides, LibreOffice, OOXML validators):

- Dangling tags relationships: the chrome-preserve path re-pointed a
  slide's tag rel at a slidewise_preserved_* name, then clobbered that
  part by re-copying the source tags under their original names. The rel
  now resolves to the de-prefixed part it should always have pointed at.
- Dangling notesMaster relationships: pptxgenjs writes a notesSlide per
  slide linked to a notes master, which chrome preservation removed
  without a source replacement. The orphaned (implicit, non-body-
  referenced) relationship is now dropped.
- SVG markup in .png raster fallbacks: dual SVG images had the SVG source
  written into the .png fallback. It is now a real rasterized PNG
  (browser) or a valid transparent PNG (SSR/Node); the svgBlip is intact.

Adds a final reconcileDanglingRels invariant guard (repair recoverable
targets, drop only safe-to-remove optional ones, keep critical rels), and
runs pruneDanglingContentTypes on the source path so stale Content_Types
overrides can't invalidate the package either. Includes unit, SVG, and a
whole-corpus validity test net.

Author: karthikmudunuri

.changeset/serialize-dangling-rels-and-svg-fallback.md

@@ -0,0 +1,31 @@
+---
+"@textcortex/slidewise": patch
+---
+
+fix(pptx): emit a structurally valid package on serialize
+
+Three `serializeDeck` bugs corrupted the generated `.pptx` (missing parts /
+invalid image bytes) even from clean source templates, triggering a PowerPoint
+repair prompt and outright rejection by stricter consumers (Google Slides,
+LibreOffice, OOXML validators):
+
+- **Dangling `tags` relationships:** the chrome-preserve path re-pointed a
+  slide's tag rel at a `slidewise_preserved_*` name, then clobbered that part by
+  re-copying the source tags under their original names. The rel now resolves
+  to the de-prefixed part it should always have pointed at.
+- **Dangling `notesMaster` relationships:** pptxgenjs writes a notesSlide per
+  slide linked to a notes master, which chrome preservation removed without a
+  source replacement. The orphaned (implicit, non-body-referenced) relationship
+  is now dropped.
+- **SVG markup in `.png` raster fallbacks:** dual SVG images (`<a:blip>` raster
+  + `<asvg:svgBlip>` vector) had the SVG source written into the `.png`
+  fallback. The fallback is now a real rasterized PNG (browser) or a valid
+  transparent PNG (SSR/Node); the vector `svgBlip` part is untouched.
+
+Adds a final `reconcileDanglingRels` invariant guard — every internal
+relationship target must resolve to a shipped part — that backstops both
+dangling-rel shapes (repairing recoverable targets, dropping only
+safe-to-remove optional ones, and leaving critical rels untouched). Also runs
+`pruneDanglingContentTypes` on the source-preservation path so stale
+`[Content_Types]` overrides (pptxgenjs's `slideMaster1..N`, leftover notes
+overrides) can't invalidate the package either.

packages/slidewise/src/lib/pptx/__tests__/chrome-preservation.test.ts

@@ -35,6 +35,22 @@ async function loadFixture(name: string): Promise<ArrayBuffer> {
 const hasEon = await fixtureExists("eon-deck.pptx");
 const hasDickinson = await fixtureExists("Dickinson_Sample_Slides.pptx");
 
+// Templates from the dangling-rel bug report (1a tags / 1b notesMaster).
+const DANGLING_FIXTURES = [
+  "Intero Master Template.pptx",
+  "Intero.pptx",
+  "44 - Education.pptx",
+  "eon-deck.pptx",
+  "Dickinson_Sample_Slides.pptx",
+] as const;
+const danglingFixtures = (
+  await Promise.all(
+    DANGLING_FIXTURES.map(async (name) =>
+      (await fixtureExists(name)) ? name : null
+    )
+  )
+).filter((n): n is (typeof DANGLING_FIXTURES)[number] => n !== null);
+
 async function listZipPaths(buf: ArrayBuffer | Blob): Promise<Set<string>> {
   const ab = buf instanceof Blob ? await buf.arrayBuffer() : buf;
   const zip = await JSZip.loadAsync(ab);
@@ -43,6 +59,52 @@ async function listZipPaths(buf: ArrayBuffer | Blob): Promise<Set<string>> {
   return paths;
 }
 
+/**
+ * Walk every `*.rels` in the package and return the internal relationship
+ * targets that don't resolve to a shipped part. A non-empty result means the
+ * output would trigger a PowerPoint repair prompt / strict-consumer rejection.
+ */
+async function findDanglingRels(
+  buf: Blob | ArrayBuffer
+): Promise<Array<{ rels: string; id: string; target: string }>> {
+  const ab = buf instanceof Blob ? await buf.arrayBuffer() : buf;
+  const zip = await JSZip.loadAsync(ab);
+  const present = new Set<string>();
+  const relsPaths: string[] = [];
+  zip.forEach((p, e) => {
+    if (e.dir) return;
+    present.add(p);
+    if (p.endsWith(".rels")) relsPaths.push(p);
+  });
+  const normalise = (target: string, base: string): string => {
+    if (target.startsWith("/")) return target.slice(1);
+    let t = target;
+    const segs = base.split("/").filter(Boolean);
+    while (t.startsWith("../")) {
+      segs.pop();
+      t = t.slice(3);
+    }
+    return [...segs, t].filter(Boolean).join("/");
+  };
+  const dangling: Array<{ rels: string; id: string; target: string }> = [];
+  for (const relsPath of relsPaths) {
+    const xml = await zip.file(relsPath)!.async("string");
+    const ownerDir = relsPath.replace(/(^|\/)_rels\/[^/]+$/, "");
+    const re = /<Relationship\b[^>]*?\/>/g;
+    let m: RegExpExecArray | null;
+    while ((m = re.exec(xml))) {
+      const tag = m[0];
+      const mode = /\bTargetMode="([^"]+)"/.exec(tag)?.[1];
+      const target = /\bTarget="([^"]+)"/.exec(tag)?.[1];
+      const id = /\bId="([^"]+)"/.exec(tag)?.[1] ?? "?";
+      if (!target || mode === "External" || /^https?:\/\//i.test(target)) continue;
+      const full = normalise(target, ownerDir === relsPath ? "" : ownerDir);
+      if (!present.has(full)) dangling.push({ rels: relsPath, id, target });
+    }
+  }
+  return dangling;
+}
+
 async function countSlidesWithSpTreeChildren(
   buf: Blob
 ): Promise<number> {
@@ -184,4 +246,23 @@ describe("deck chrome preservation", () => {
       expect(fontCount).toBe(5);
     }
   );
+
+  // Package invariant: no internal relationship may point at a missing part.
+  // Catches the tags (1a) and notesMaster (1b) danglers the chrome-preserve
+  // path used to emit. Runs per available fixture (skipped in CI where the
+  // branded decks aren't committed).
+  for (const name of danglingFixtures) {
+    it(`emits no dangling internal relationships (${name})`, async () => {
+      const source = await loadFixture(name);
+      const deck = await parsePptx(source);
+      const blob = await serializeDeck(deck, { source });
+      const dangling = await findDanglingRels(blob);
+      expect(
+        dangling,
+        `dangling rels:\n${dangling
+          .map((d) => `  ${d.rels} ${d.id} → ${d.target}`)
+          .join("\n")}`
+      ).toEqual([]);
+    });
+  }
 });

packages/slidewise/src/lib/pptx/__tests__/corpus-validity.test.ts

@@ -0,0 +1,175 @@
+import { describe, it, expect } from "vitest";
+import { readFile, readdir } from "node:fs/promises";
+import { fileURLToPath } from "node:url";
+import path from "node:path";
+import JSZip from "jszip";
+import { parsePptx, serializeDeck } from "../index";
+
+/**
+ * Whole-corpus structural-validity net. Drop any number of `.pptx` files into
+ * the gitignored `.context/attachments/` dir (the same place the other fixture
+ * tests read from) and this round-trips EVERY one through
+ * `parsePptx → serializeDeck`, asserting the output is a structurally valid
+ * OOXML package:
+ *
+ *   1. every internal relationship target resolves to a shipped part,
+ *   2. every `[Content_Types]` Override points at a part that exists,
+ *   3. every shipped part has a declared content type (Default by extension
+ *      or an explicit Override),
+ *   4. every `ppt/media/*.png` holds real PNG bytes (never SVG markup).
+ *
+ * These are exactly the four ways the reported bugs corrupted the artifact.
+ * The whole suite skips when no decks are present, so CI stays green for
+ * outside contributors while it scans the full corpus locally.
+ */
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const attachmentsDir = path.resolve(
+  __dirname,
+  "../../../../../../.context/attachments"
+);
+
+async function findPptx(dir: string): Promise<string[]> {
+  const out: string[] = [];
+  let entries;
+  try {
+    entries = await readdir(dir, { withFileTypes: true });
+  } catch {
+    return out;
+  }
+  for (const e of entries) {
+    const full = path.join(dir, e.name);
+    if (e.isDirectory()) out.push(...(await findPptx(full)));
+    else if (/\.(pptx|potx)$/i.test(e.name)) out.push(full);
+  }
+  return out;
+}
+
+function normalise(target: string, base: string): string {
+  if (target.startsWith("/")) return target.slice(1);
+  let t = target;
+  const segs = base.split("/").filter(Boolean);
+  while (t.startsWith("../")) {
+    segs.pop();
+    t = t.slice(3);
+  }
+  return [...segs, t].filter(Boolean).join("/");
+}
+
+const PNG_MAGIC = [0x89, 0x50, 0x4e, 0x47];
+
+interface Problems {
+  danglingRels: string[];
+  danglingOverrides: string[];
+  undeclaredParts: string[];
+  invalidPngs: string[];
+}
+
+async function validate(buf: ArrayBuffer): Promise<Problems> {
+  const zip = await JSZip.loadAsync(buf);
+  const present = new Set<string>();
+  const relsPaths: string[] = [];
+  const mediaPngs: string[] = [];
+  zip.forEach((p, e) => {
+    if (e.dir) return;
+    present.add(p);
+    if (p.endsWith(".rels")) relsPaths.push(p);
+    if (/^ppt\/media\/.+\.png$/i.test(p)) mediaPngs.push(p);
+  });
+
+  const problems: Problems = {
+    danglingRels: [],
+    danglingOverrides: [],
+    undeclaredParts: [],
+    invalidPngs: [],
+  };
+
+  // 1. Relationship targets.
+  for (const relsPath of relsPaths) {
+    const xml = await zip.file(relsPath)!.async("string");
+    const ownerDir = relsPath.replace(/(^|\/)_rels\/[^/]+$/, "");
+    const base = ownerDir === relsPath ? "" : ownerDir;
+    const re = /<Relationship\b[^>]*?\/>/g;
+    let m: RegExpExecArray | null;
+    while ((m = re.exec(xml))) {
+      const tag = m[0];
+      const mode = /\bTargetMode="([^"]+)"/.exec(tag)?.[1];
+      const target = /\bTarget="([^"]+)"/.exec(tag)?.[1];
+      const id = /\bId="([^"]+)"/.exec(tag)?.[1] ?? "?";
+      if (!target || mode === "External" || /^https?:\/\//i.test(target)) continue;
+      if (!present.has(normalise(target, base))) {
+        problems.danglingRels.push(`${relsPath} ${id} → ${target}`);
+      }
+    }
+  }
+
+  // 2 + 3. Content types.
+  const ct = await zip.file("[Content_Types].xml")?.async("string");
+  if (ct) {
+    const defaults = new Set<string>();
+    const overrides = new Set<string>();
+    let dm: RegExpExecArray | null;
+    const defRe = /<Default\b[^>]*Extension="([^"]+)"[^>]*\/>/g;
+    while ((dm = defRe.exec(ct))) defaults.add(dm[1].toLowerCase());
+    const ovRe = /<Override\b[^>]*PartName="([^"]+)"[^>]*\/>/g;
+    let om: RegExpExecArray | null;
+    while ((om = ovRe.exec(ct))) {
+      overrides.add(om[1]);
+      if (!present.has(om[1].replace(/^\//, ""))) {
+        problems.danglingOverrides.push(om[1]);
+      }
+    }
+    for (const p of present) {
+      if (p === "[Content_Types].xml" || p.endsWith(".rels")) continue;
+      const ext = (p.split(".").pop() ?? "").toLowerCase();
+      if (defaults.has(ext) || overrides.has("/" + p)) continue;
+      problems.undeclaredParts.push(p);
+    }
+  }
+
+  // 4. PNG media bytes.
+  for (const p of mediaPngs) {
+    const bytes = await zip.file(p)!.async("uint8array");
+    const ok =
+      bytes.length >= 4 && PNG_MAGIC.every((b, i) => bytes[i] === b);
+    if (!ok) problems.invalidPngs.push(p);
+  }
+
+  return problems;
+}
+
+const decks = await findPptx(attachmentsDir);
+
+describe.skipIf(decks.length === 0)("corpus structural validity", () => {
+  it.each(decks)("serializes a valid package: %s", async (deckPath) => {
+    const file = await readFile(deckPath);
+    const source = file.buffer.slice(
+      file.byteOffset,
+      file.byteOffset + file.byteLength
+    ) as ArrayBuffer;
+
+    const deck = await parsePptx(source);
+    const blob = await serializeDeck(deck, { source });
+    const problems = await validate(await blob.arrayBuffer());
+
+    const summary = [
+      problems.danglingRels.length
+        ? `dangling rels:\n  ${problems.danglingRels.join("\n  ")}`
+        : "",
+      problems.danglingOverrides.length
+        ? `Content_Types overrides with no part:\n  ${problems.danglingOverrides.join("\n  ")}`
+        : "",
+      problems.undeclaredParts.length
+        ? `parts with no content type:\n  ${problems.undeclaredParts.join("\n  ")}`
+        : "",
+      problems.invalidPngs.length
+        ? `.png parts holding non-PNG bytes:\n  ${problems.invalidPngs.join("\n  ")}`
+        : "",
+    ]
+      .filter(Boolean)
+      .join("\n");
+
+    expect(summary, summary || undefined).toBe("");
+  });
+});