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fix(pdf-server): radio + dropdown in fill_form/save (#577)

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* fix(pdf-server): fail fast on never-polled viewer + surface batch errors

interact's get_screenshot/get_text waited the full 45s for a viewer that
never mounted (host went idle before iframe reached startPolling), then
timed out with a generic message. Now tracks viewsPolled and fails in ~8s
with a recovery hint. Batch errors were also ordered success-first —
hosts that flatten isError to content[0] showed "Queued: Filled N fields"
and dropped the actual failure entirely. Viewer side: poll even when PDF
load throws, and catch connect() rejection instead of silently blanking.

* fix(pdf-server): radio button + dropdown handling in fill_form and save

Three related bugs around non-text form fields:

Viewer fill_form (mcp-app.ts): writing a string to annotationStorage on
every radio widget trips pdf.js's inverted string coercion
(`value !== buttonValue` → true) — the first-rendered widget checks
itself and clears the rest, so whatever you ask for, you get the first
option. Fix: extract a setFieldInStorage() helper that writes
{value: true} only on the widget whose buttonValue matches, {value: false}
on siblings, matching pdf.js's own change handler. Also covers the
syncFormValuesToStorage() path (localStorage restore).

Save (pdf-annotations.ts): buildAnnotatedPdfBytes only knew about
getTextField/getCheckBox — dropdowns and radios threw in the try block
and fell through the catch, so they were silently dropped on save.
Fix: instanceof dispatch on getFieldMaybe(). For radios, accept either
the option label or a numeric buttonValue (indexed into getOptions()),
since the viewer stores the latter for PDFs with /Opt.

display_pdf output (server.ts): radio groups showed as N identical
`name [Btn]` lines with no way to tell them apart; dropdowns didn't
list their options. Fix: surface buttonValue as exportValue and the
options array from the annotation data already in hand.
This commit is contained in:
Olivier Chafik 2026-04-01 22:28:28 +01:00 • committed by GitHub
commit 38700569e7
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1 changed files with 434 additions and 72 deletions
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45
examples/pdf-server/src/pdf-annotations.ts
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@ -18,6 +18,10 @@ import {
PDFString,
PDFHexString,
StandardFonts,
PDFTextField,
PDFCheckBox,
PDFDropdown,
PDFRadioGroup,
} from "pdf-lib";
// =============================================================================
@ -810,26 +814,45 @@ export async function buildAnnotatedPdfBytes(
// Add proper PDF annotation objects
await addAnnotationDicts(pdfDoc, annotations);
// Apply form fills
// Apply form fills. Dispatch on actual field type — getTextField(name) throws
// for dropdowns/radios, so the old try/catch silently dropped those on save.
if (formFields.size > 0) {
try {
const form = pdfDoc.getForm();
for (const [name, value] of formFields) {
try {
if (typeof value === "boolean") {
const checkbox = form.getCheckBox(name);
if (value) checkbox.check();
else checkbox.uncheck();
const field = form.getFieldMaybe(name);
if (!field) continue;
if (field instanceof PDFCheckBox) {
if (value) field.check();
else field.uncheck();
} else if (field instanceof PDFRadioGroup) {
// The viewer stores pdf.js's buttonValue, which for PDFs with an
// /Opt array is a numeric index ("0","1","2") rather than the
// option label pdf-lib's select() expects. Try the label first,
// then fall back to indexing into getOptions().
const opts = field.getOptions();
const s = String(value);
if (opts.includes(s)) {
field.select(s);
} else {
const textField = form.getTextField(name);
textField.setText(value);
const idx = Number(s);
if (Number.isInteger(idx) && idx >= 0 && idx < opts.length) {
field.select(opts[idx]);
}
// else: value is neither label nor index — leave unset
}
} catch {
// Field not found or wrong type — skip
} else if (field instanceof PDFDropdown) {
// select() auto-enables edit mode for values outside getOptions(),
// so this works for both enumerated and free-text combos.
field.select(String(value));
} else if (field instanceof PDFTextField) {
field.setText(String(value));
}
// PDFButton, PDFOptionList, PDFSignature: no fill_form support yet
}
} catch {
// Form not available — skip
// pdfDoc.getForm() throws if the PDF has no AcroForm
}
}