UN-3185 [FIX] Install global Prism unconditionally + correct rationale (review)

ritwik-g · claude · ritwik-g · commit 5ad4e789bd01 · 2026-07-01T12:13:12.000+05:30
Address PR review:
- silent-failure-hunter: a `!globalThis.Prism` guard could leave a different,
  pre-existing Prism in place, so the add-ons extend one instance while
  JsonView's highlightAll() reads another -&gt; JSON silently unhighlighted.
  Assign unconditionally so the global is provably our core instance.
- comment-analyzer: the prior comment blamed evaluation order yet relied on it
  to justify the fix. Rewrite: relying on prismjs core's self-install is
  unreliable under code-splitting; the explicit globalThis assignment (from
  first-party code imported before the add-ons) is the deterministic fix.

Rebuilt: emitted chunk runs `globalThis.Prism = &lt;core&gt;` immediately before
`Prism.languages.json = ...`.

Co-Authored-By: Claude Opus 4.8 &lt;noreply@anthropic.com&gt;
diff --git a/frontend/src/helpers/prismSetup.js b/frontend/src/helpers/prismSetup.js
@@ -1,19 +1,19 @@
 import Prism from "prismjs";
 
-// prismjs language/plugin add-ons (`prismjs/components/*`, `prismjs/plugins/*`)
-// reference a *bare global* `Prism` and carry no import edge back to prismjs
-// core. Under the Vite (ESM + code-split) build there is no guarantee the plain
-// side-effect `import "prismjs"` evaluates — and installs that global — before
-// those add-ons run, so they threw `ReferenceError: Prism is not defined`,
-// crashing Combined Output (Prompt Studio detail page + HITL review).
+// The prismjs add-ons imported alongside this module (`prismjs/components/*`,
+// `prismjs/plugins/*`) register their grammars onto a *bare global* `Prism` and
+// carry no import edge back to prismjs core. Leaving that global to prismjs
+// core's own self-install is unreliable under Vite's code-split production
+// build: the add-ons evaluated before anything installed `Prism`, throwing
+// `ReferenceError: Prism is not defined` and blanking Combined Output (Prompt
+// Studio detail page + HITL review).
 //
-// Import THIS module before any add-on: it is a real dependency edge whose
-// `Prism` binding is used below (so it survives tree-shaking, unlike a bare
-// side-effect import), and its body pins core on the global. A sibling
-// dependency is fully evaluated — body included — before the next one, so the
-// global is guaranteed to exist by the time the add-on modules evaluate.
-if (!globalThis.Prism) {
-  globalThis.Prism = Prism;
-}
+// Make it deterministic: the used `Prism` binding forces the bundler to retain
+// and evaluate core, and this module — imported before the add-ons — pins it on
+// the global so it exists by the time they register. Assign unconditionally:
+// the global must be THIS instance, the one the add-ons extend and that
+// JsonView's `Prism.highlightAll()` reads. A `!globalThis.Prism` guard could
+// leave a different, pre-existing Prism in place and silently drop highlighting.
+globalThis.Prism = Prism;
 
 export default Prism;
