View formatting lands on the wrong view — and a missing column is not an empty string

Symptom

A library you format from code looks broken: cards with no title, placeholder thumbnails, and a date that renders as a lone 1. — while the same formatter works fine on your own lists.

Cause

Two independent mistakes that meet in the middle.

1. The view lookup is too forgiving. A typical resolver:

// pick AllItems.aspx…
let pick = views.find(v => v.ServerRelativeUrl.toLowerCase().includes('/allitems.aspx'));
// …otherwise "the default view", whatever that is
if (!pick) pick = views.find(v => v.DefaultView);

For Site Pages the first branch never matches, and the second one happily hands you ByAuthor.aspx, ByEditor.aspx or RecentChanges.aspx — views that group by a field and carry a different column set.

2. The columns were never really added. Formatting code often adds view fields best-effort (try { addviewfield } catch { /* ignore */ }) and, on the "only add what's missing" path, forgets Title entirely. addviewfield on a column that does not exist on the list fails quietly, so nothing is added and nothing is reported.

The rendering consequence is the part people get wrong: for a column not present in the view, [$Column] is not an empty string. =if([$Column] == '', 'none', 'inline-flex') is therefore false and the element stays visible, empty. Date helpers degrade the same way — getDate('') yields 1 while getMonth('') and getYear('') produce nothing, which is where the stray 1. comes from.

Fix

Only ever format an all-items view, and never a specialised one:

const isAll = (v) => {
  const u = (v.ServerRelativeUrl || '').toLowerCase();
  return u.indexOf('/allitems.aspx') !== -1 || u.indexOf('/allpages.aspx') !== -1;
};
let pick = views.filter(v => !v.Hidden).find(v => isAll(v) && v.DefaultView)
        ?? views.filter(v => !v.Hidden).find(isAll);
if (!pick) return false;   // no all-items view → format nothing

Read the columns back and fail closed:

await addMissingViewFields(viewUrl, ['Title', ...fields]);
const after = (await readViewFields(viewUrl)).map(f => f.toLowerCase());
if (!['Title', ...fields].every(f => after.includes(f.toLowerCase()))) return false;  // skip the formatter
await mergeView(viewUrl, { ViewType2: tile ? 'TILES' : '', CustomFormatter: escaped });

A default table beats a broken card. And do not flip DefaultView on a library that SharePoint owns (Site Pages, Documents) — changing which view users land on is the site owner's call, not your provisioning code's.

How to tell whether your code touched a view

ViewType2 is null on views nobody has formatted and a string ('' for List, 'TILES' for Gallery) on views that were written to:

GET /_api/web/GetList('/sites/team/SitePages')/views?$select=Title,DefaultView,Hidden,ServerRelativeUrl,ViewType2

To undo it in the UI: open the view → Format view → clear the JSON box → Save.

Related

• An empty date is not an empty string in formatting
• Gallery cards render from tileProps
• View formatter rejects < and &