fix: throw clean lookup error for view names ending with a dot

[haoku123]

Problem

Closes #7350

A view name ending in . makes path.extname('index.') return '.', which is truthy, so the "no extension → use default engine" fallback in lib/view.js is skipped. this.ext stays '.', this.ext.slice(1) becomes '', and require('') is called, throwing an opaque ERR_INVALID_ARG_VALUE TypeError instead of resolving the view or reporting a clean lookup error.

Via res.render('index.') inside a route, the same error surfaces as an opaque 500 in the error handler instead of the usual Failed to lookup view "index." error.

Solution

Treat a bare . as no extension so the default engine is applied and view resolution reports a clean lookup error through the callback:

// a name ending in "." yields a bare "." from extname(), which is not a
// usable extension; treat it as no extension so the default engine is
// applied and a clean lookup error is reported instead of require("")
if (this.ext === '.') {
  this.ext = '';
}

Tests

Added when the view name ends with a "." to test/app.render.js verifying the callback receives the standard Failed to lookup view "user." error rather than ERR_INVALID_ARG_VALUE. Full suite passes (npm test → 1264 passing), lint clean.

Note

Re-implements the stalled #7351 (author inactive since July) on current master, with the same behavior and test coverage.

[krzysdz]

PRs can always be picked up by maintainers (if the appropriate option is selected). I don't see any requested changes in #7351, so I'll close this as a duplicate.