PR comments: add try catch while accessing theme from localStorage #12682

dixita0607 · 2025-11-13T16:43:50Z

A follow up PR resolving PR comments on #12673 by Gemini code assist

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gemini-code-assist · 2025-11-13T16:44:04Z

Summary of Changes

Hello @dixita0607, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the resilience of the website's theme loading mechanism. By encapsulating the localStorage access within a try-catch block, the system can now gracefully handle scenarios where localStorage is not available or restricted, preventing errors and ensuring that the site can still render with a default theme.

Highlights

Robustness: Implemented a try-catch block around the JavaScript code that accesses localStorage to retrieve theme preferences.
Error Handling: This change prevents potential runtime errors in environments where localStorage might be unavailable or restricted, ensuring a more stable user experience.
Theme Fallback: If localStorage is inaccessible, the theme loading logic will now gracefully fail without breaking, allowing the site to fall back to its default theme.

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gemini-code-assist

Code Review

This pull request correctly adds a try-catch block to handle potential errors when accessing localStorage for theme settings. This is a good improvement for robustness.

I've added one suggestion to slightly optimize the script by moving a variable declaration into the scope where it's used.

Additionally, I noticed that localStorage is also accessed in site/lib/src/components/layout/theme_switcher.dart when setting the theme, which could also benefit from being wrapped in a try-catch block. This is outside the scope of this PR, but it would be great to address it in a follow-up to ensure consistent error handling across the theme-related logic.

gemini-code-assist · 2025-11-13T16:45:15Z

site/lib/src/layouts/dash_layout.dart

+  const prefersDarkMode = window.matchMedia('(prefers-color-scheme: dark)');

-const storedTheme = window.localStorage.getItem('theme') ?? 'light-mode';
-if (storedTheme === 'auto-mode') {
-  document.body.classList.add(
-      'auto-mode',
-      prefersDarkMode.matches ? 'dark-mode' : 'light-mode',
-  );
-} else {
-  document.body.classList.add(storedTheme);
+  const storedTheme = window.localStorage.getItem('theme') ?? 'light-mode';
+  if (storedTheme === 'auto-mode') {
+    document.body.classList.add(
+        'auto-mode',
+        prefersDarkMode.matches ? 'dark-mode' : 'light-mode',
+    );
+  } else {
+    document.body.classList.add(storedTheme);
+  }


For a minor performance improvement and to scope variables more tightly, you can move the prefersDarkMode declaration inside the if (storedTheme === 'auto-mode') block, since it's only used there. This avoids an unnecessary call to window.matchMedia when the theme is not set to 'auto-mode'.

Suggested change

const prefersDarkMode = window.matchMedia('(prefers-color-scheme: dark)');

const storedTheme = window.localStorage.getItem('theme') ?? 'light-mode';

if (storedTheme === 'auto-mode') {

document.body.classList.add(

'auto-mode',

prefersDarkMode.matches ? 'dark-mode' : 'light-mode',

);

} else {

document.body.classList.add(storedTheme);

const storedTheme = window.localStorage.getItem('theme') ?? 'light-mode';

if (storedTheme === 'auto-mode') {

document.body.classList.add(

'auto-mode',

prefersDarkMode.matches ? 'dark-mode' : 'light-mode',

);

} else {

document.body.classList.add(storedTheme);

}

const storedTheme = window.localStorage.getItem('theme') ?? 'light-mode';

if (storedTheme === 'auto-mode') {

const prefersDarkMode = window.matchMedia('(prefers-color-scheme: dark)');

document.body.classList.add(

'auto-mode',

prefersDarkMode.matches ? 'dark-mode' : 'light-mode',

);

} else {

document.body.classList.add(storedTheme);

}

dixita0607 · 2025-11-13T16:48:30Z

@parlough While making this change, I notice three more file not having a try catch while accessing localStorage

Should I go ahead with the same change in them too?

Also I think if this is okay, I can make a PR on dart's website repo too.

parlough · 2025-11-13T21:17:49Z

While making this change, I notice three more files not having a try catch while accessing localStorage.

Should I go ahead with the same change in them too?

Thanks for checking for other locations @dixita0607! I think it makes sense to make those other usages more resilient as well, so sure. Let me know if you have any questions about how to handle any of those cases.

- This is an extension of a PR comment recommended by Gemini code assist in another PR - For now, the catch blocks prints the errors if the app is running in the debug mode

dixita0607 · 2025-11-14T15:45:17Z

site/lib/src/client/global_scripts.dart

-            'tab-save-$currentSaveKey',
-            currentSaveId,
-          );
+          try {


Hi @parlough I added the changes in the rest of the files. For now I have added some print statements in debug mode. Please feel free to direct me if we need to perform other actions there.

Also, it'd be great if you can give tips on testing this.

flutter-website-bot · 2025-11-15T00:12:00Z

Visit the preview URL for this PR (updated for commit 412cb7c):

https://flutter-docs-prod--pr12682-12673-work-on-pr-comments-gv1od254.web.app

refactor: add try catch while accessing theme from localStorage

44f4a77

dixita0607 requested review from a team and sfshaza2 as code owners November 13, 2025 16:43

gemini-code-assist bot reviewed Nov 13, 2025

View reviewed changes

fix: wrap code accessing localStorage a try catch block

412cb7c

- This is an extension of a PR comment recommended by Gemini code assist in another PR - For now, the catch blocks prints the errors if the app is running in the debug mode

dixita0607 commented Nov 14, 2025

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PR comments: add try catch while accessing theme from localStorage #12682

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dixita0607 commented Nov 13, 2025

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parlough commented Nov 13, 2025 •

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