fix(app): support runtime base paths for subpath deployments

[nutzlastfan]

Context

This ports the runtime base-path work from a downstream OHIF 3.11 deployment into current upstream master.

The main issue is that a single build still assumes a fixed build-time PUBLIC_URL, which breaks chunk loading, dynamic extension imports, and PWA asset resolution when the viewer is mounted under a subpath instead of /.

Changes

• add shared runtime public-path helpers in @ohif/core
• set webpack public path at runtime before the app bootstraps
• switch generated plugin imports to resolve non-HTTP assets through the runtime base path
• make the PWA template emit relative asset paths and derive the base path in the HTML head
• make manifest icon paths relative so they work under subpath deployments

Result

A single viewer build can resolve static assets and dynamic imports correctly when served from paths like /some-prefix/viewer/... instead of only from the site root.

Notes

• This PR intentionally keeps the scope on runtime base-path handling.
• I opened it as a draft because upstream may prefer a different bootstrap shape for the early base-path script.

Greptile Summary

This PR ports runtime base-path support from a downstream OHIF 3.11 deployment, enabling a single build to be served from any subpath (e.g. /some-prefix/viewer/) by resolving __webpack_public_path__, chunk loading, PWA assets, and dynamic extension imports at runtime rather than at build time. The approach is sound — the webpack publicPath: '' + runtime assignment pattern is correct, and placing setRuntimePublicPath as the first import in index.js ensures the public path is set before any dynamic chunk loading.

Confidence Score: 4/5

Safe to merge once the open heuristic bug (viewerIndex guard, already tracked in prior threads) is resolved; remaining new findings are P2

The two new P2 findings — raw TS source import in platform/app/src/utils/publicUrl.ts and the missing leading slash on historyApiFallback.index — are minor. The score is held at 4 rather than 5 because the viewerIndex >= 0 correctness bug discussed in prior threads (affecting /viewer/-prefixed deployments) remains unresolved across publicUrl.ts, index.html, and rollbar.html.

platform/core/src/utils/publicUrl.ts, platform/app/public/html-templates/index.html, platform/app/public/html-templates/rollbar.html — all share the unguarded viewerIndex >= 0 heuristic; platform/app/src/utils/publicUrl.ts — direct TS source import

Important Files Changed

Filename	Overview
platform/core/src/utils/publicUrl.ts	New canonical module for runtime base-path logic; contains the known viewerIndex >= 0 heuristic bug (already flagged in existing threads) that resolves to the wrong path when the deployment prefix itself starts with /viewer
platform/app/src/setRuntimePublicPath.js	Sets __webpack_public_path__, window.__OHIF_BASE_PATH__, and window.PUBLIC_URL at boot; now correctly imports from @ohif/core and is the first import in index.js
platform/app/src/utils/publicUrl.ts	New app-level utility wrapper; still imports from the raw ../../../core/src/utils/publicUrl TS source instead of @ohif/core, the same coupling that was fixed in setRuntimePublicPath.js
platform/app/public/html-templates/index.html	Adds inline base-path bootstrap script that sets window.__OHIF_BASE_PATH__ and a <base> element before assets load; shares the known viewerIndex >= 0 bug with the canonical TS module
platform/app/public/html-templates/rollbar.html	Verbatim copy of the same bootstrap script as index.html; inherits the same viewerIndex >= 0 heuristic issue
platform/app/.webpack/webpack.pwa.js	Drops fixed PUBLIC_URL in favour of empty-string publicPath so runtime __webpack_public_path__ takes over; historyApiFallback.index loses its leading / which breaks the dev-server SPA fallback
platform/app/.webpack/writePluginImportsFile.js	Generates pluginImports.js with a getRuntimeImportPath helper that routes non-HTTP import paths through getPublicSubPath, correctly handling subpath deployments
platform/app/public/manifest.json	Icon paths changed to relative (assets/… without leading /), allowing the manifest to resolve correctly under any subpath
platform/core/src/utils/index.ts	Exports the five new publicUrl utilities through the package surface; straightforward additions
platform/core/src/index.ts	Re-exports the new utilities at the top-level @ohif/core package boundary; straightforward additions
platform/app/src/index.js	Adds import './setRuntimePublicPath' as the first import, ensuring __webpack_public_path__ is set before any dynamic chunk loading occurs

Prompt To Fix All With AI

This is a comment left during a code review.
Path: platform/app/src/utils/publicUrl.ts
Line: 1

Comment:
**Direct import from raw TypeScript source**

This file imports from `'../../../core/src/utils/publicUrl'` (the raw `.ts` source) instead of the published `@ohif/core` package — the same pattern that was flagged and already fixed in `setRuntimePublicPath.js`. While it works in a monorepo build, it bypasses the package boundary and will break if `@ohif/core` ever ships pre-compiled or if the internal path is reorganized.

```suggestion
import { normalizePublicUrl, toRouterBasename } from '@ohif/core';
```

How can I resolve this? If you propose a fix, please make it concise.

---

This is a comment left during a code review.
Path: platform/app/.webpack/webpack.pwa.js
Line: 176

Comment:
**`historyApiFallback.index` missing leading slash**

The old value was `PUBLIC_URL + 'index.html'` which defaulted to `'/index.html'`. The replacement drops the leading `/`. The `connect-history-api-fallback` middleware (used internally by webpack-dev-server) expects a root-relative path beginning with `/`; without it the SPA fallback won't serve `index.html` for unmatched routes during local development.

```suggestion
        index: '/index.html',
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (2): Last reviewed commit: "fix(app): derive base path from last vie..." | Re-trigger Greptile}

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