Failed to render template "${sourcePath}". This may break th

Error message

Failed to render template "${sourcePath}". This may break the App Extension...

What it means

During App Extension installation, renderFile copies template files and renders placeholders like <%= ... %> via Lodash-style templates. If template compilation/rendering throws, the content equals the sentinel templateRenderError and only this warning is emitted; the file is skipped (not written to the target). The extension's prompts/inject may then be incomplete and break at runtime.

Source

Thrown at app-vite/lib/app-extension/AppExtensionInstance.js:68

  if (overwritePrompt && fse.existsSync(targetPath)) {
    const action = await promptOverwrite({
      targetPath,
      options: ['overwrite', 'skip'],
      ctx
    })

    if (action === 'skip') return
  }

  if (rawCopy || isBinaryFile(sourcePath)) {
    fse.ensureFileSync(targetPath)
    fse.copyFileSync(sourcePath, targetPath)
  } else {
    const rawContent = fse.readFileSync(sourcePath, 'utf8')
    const content = renderTemplate(rawContent, scope, renderTemplateCompileOpts)

    if (content === templateRenderError) {
      logger.warn(
        `Failed to render template "${sourcePath}". This may break the App Extension...`
      )
    } else {
      fse.ensureFileSync(targetPath)
      fse.writeFileSync(targetPath, content, 'utf8')
    }
  }
}

async function renderFolders({ source, rawCopy, scope }, ctx, logger) {
  let overwrite
  const { globSync } = await import('tinyglobby')
  const files = globSync(['**/*'], { cwd: source })

  for (const rawPath of files) {
    const targetRelativePath = rawPath
      .split('/')
      .map(name => {

View on GitHub (pinned to 4841521b5f)

Solutions

Open the logged sourcePath and fix the template syntax around the failing expression
Report/patch the App Extension (update it to a version with the template fixed)
As a workaround, copy the file manually into the target path with placeholders pre-resolved
Re-run the extension install after fixing to regenerate the skipped file

Example fix

// before (template file, unbalanced tag)
const x = <%= data.x %
// after
const x = <%= data.x %>

Defensive patterns

Strategy: validation

Validate before calling

// sanity-check extension templates before shipping/publishing
const fs = require('fs')
for (const f of templateFiles) {
  const src = fs.readFileSync(f, 'utf8')
  const opens = (src.match(/<%=/g) || []).length
  const closes = (src.match(/%>/g) || []).length
  if (opens !== closes) throw new Error(`Unbalanced EJS tags in ${f}`)
}

Prevention

Escape literal ${ and template-like syntax in template files
Test `quasar ext add` of your extension in a scratch app before publishing
Include template files in the npm package and keep them free of renderer-unsupported syntax
After install, diff generated files against templates to catch silently skipped renders

When it happens

Trigger: A template file in the extension's /template folder contains syntax that fails renderTemplate compilation (e.g. unbalanced <%= %>, ES template literal syntax unsupported by the compile options) during ext install or runInstallScript's renderFolders.

Common situations: Third-party App Extension shipped with a broken template; template containing code with `${...}` or special characters clashing with the template engine; extension written for an older Quasar template renderer.

Related errors

AI-assisted analysis of quasarframework/quasar@4841521b5f (2026-08-30). Data as JSON: /api/errors/545b1c0b1779f84e. Report an issue: GitHub.