fix(prerender): check for web/dist/index.html before detecting routes

[lisa-assistant]

Background

In packages/cli/src/commands/prerenderHandler.ts at line 206:

// TODO: This should come before we even bother detecting routes to prerender
const indexHtmlPath = path.join(getPaths().web.dist, 'index.html')

if (!fs.existsSync(indexHtmlPath)) {
  console.error(
    `You must run \`${formatCedarCommand(['build', 'web'])}\` before trying to prerender.`,
  )
  process.exit(1)
}

The prerender command currently:

1. Runs detectPrerenderRoutes() to find all routes marked for prerendering (~line 188)
2. Filters to routes with paths
3. Bails out if no prerender routes found
4. Then checks if web/dist/index.html exists — only now will it tell the user they forgot to build first

What needs to be done

Move the index.html existence check to the top of the handler, before route detection begins.

Why: Route detection may involve importing project code (Babel transforms, module loading). If web/dist doesn't exist, this is always going to fail — it's wasteful to do the detection work first. More importantly, the user gets a clearer, faster error message: "you need to build first" rather than potentially seeing a confusing detection error.

Change

In packages/cli/src/commands/prerenderHandler.ts, move the indexHtmlPath block (lines 206–214) to just after the getPaths() / import setup, before the detectPrerenderRoutes() call at line 188.

Before:

detectPrerenderRoutes() → filter routes → check no routes → check index.html → prerender

After:

check index.html → detectPrerenderRoutes() → filter routes → check no routes → prerender

This is a pure reorder with no logic changes — the behavior in the happy path is identical.

File

packages/cli/src/commands/prerenderHandler.ts, line 206

[lisa-assistant]

Self-fix confidence: 9/10
Pure code reorder with no logic changes — very low risk. Just need to verify the moved check has access to the same imported utilities (, ) that are already available at the top of the function.

[lisa-assistant]

Implementation Plan

Goal: Fail fast if web/dist/index.html doesn't exist — before spending time detecting routes.

File to change

packages/cli/src/commands/prerenderHandler.ts

---

Current flow in getTasks() (lines ~184–216)

1. dynamic import of @cedarjs/prerender/detection
2. detectPrerenderRoutes()
3. filter + normalise routes
4. (early return if no prerender routes)
5. ← check for index.html  ← this is where process.exit(1) happens today
6. configureBabel()
7. expandRouteParameters + build Listr tasks

Fix: move the check to before step 1

export const getTasks = async (
  dryrun: boolean,
  routerPathFilter: string | null = null,
) => {
  // ✅ Moved here — check before doing any route detection work
  const indexHtmlPath = path.join(getPaths().web.dist, 'index.html')
  if (!fs.existsSync(indexHtmlPath)) {
    console.error(
      `You must run \`${formatCedarCommand(['build', 'web'])}\` before trying to prerender.`,
    )
    process.exit(1)
  }

  const detector = projectIsEsm()
    ? await import('@cedarjs/prerender/detection')
    : await import('@cedarjs/prerender/cjs/detection')
  // ...
}

The four names it references (path, fs, getPaths, formatCedarCommand) are all module-level imports already in the file — nothing new needed.

Remove the original block at lines 206–214 (including the TODO comment).

---

Why this matters

If the user runs cedar prerender without first running cedar build web, the current code wastes time importing the prerender detector and traversing the route tree, only to bail out afterwards. Moving the check to the top gives an immediate, clear error message with no unnecessary work.

---

Edge cases

• dryrun mode: The dry-run path flows through getTasks too — the early exit is correct there as well (you still need the built index.html to actually prerender anything).
• No prerender routes: The prerenderRoutes.length === 0 early return is a softer "nothing to do" path; the index.html check should come after that return so users who haven't marked any routes for prerender don't get a misleading error about missing build output. Alternatively, swap the two checks. Either order is defensible — I'd suggest keeping the "no routes" check first so the error message is maximally specific.

---

Test to update / add

Look at packages/prerender/src/__tests__/ or the CLI integration tests for prerender. Add a test that calls getTasks() when index.html is absent and asserts process.exit(1) is called before detectPrerenderRoutes is invoked.