Fix plugin loading error ('fn4 is not a function') via bundling#499
Merged
Tarquinen merged 4 commits intoOpencode-DCP:devfrom Apr 12, 2026
Merged
Fix plugin loading error ('fn4 is not a function') via bundling#499Tarquinen merged 4 commits intoOpencode-DCP:devfrom
Tarquinen merged 4 commits intoOpencode-DCP:devfrom
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This fixes the 'fn4 is not a function' error when the plugin is loaded by opencode (which runs on Bun).
The issue occurs because the generated JavaScript files from standard `tsc` contain extensionless relative imports (e.g. `import { ... } from "./lib/config"`), which breaks Node.js ESM module resolution requirements. It also breaks for the `jsonc-parser` dependency which ships an ESM build with the same issue.
By using `tsup` to bundle the project into a single `dist/index.js` file and inlining `jsonc-parser`, we eliminate all relative ESM import errors entirely while keeping the source code clean.
Collaborator
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Yea this actually looks good, thank you for your help. Not sure yet when I'll do another release as there's a number of other things that need to be fixed due to opencode plugin and sdk changes but should be soon. |
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Problem
When opencode (which runs on Bun) attempts to load the
@tarquinen/opencode-dcpplugin, it crashes with the error:fn4 is not a function. (In 'fn4(input)', 'fn4' is an instance of Object) failed to load pluginThis obscure internal Bun/JIT error occurs when it fails to resolve ESM imports during plugin instantiation. The compiled
dist/output from standardtsccontains extensionless relative imports (e.g.import { getConfig } from "./lib/config"instead of./lib/config.js), which breaks modern Node.js and Bun strict ESM module resolution.Additionally, the dependency
jsonc-parserships a broken ESM build that contains these exact same extensionless errors internally, meaning even patching the local TS imports wouldn't fully fix it.Solution
Instead of emitting raw transpiled files via
tsc(which would require rewriting all internal imports and abandoningjsonc-parser), this PR usestsupto bundle the plugin into a single, cleandist/index.jsfile.tsupfor compilation and bundling.jsonc-parserexplicitly intsup.config.tsso its internal imports are resolved ahead of time..d.tsdeclaration emission viatsc --emitDeclarationOnly.This fixes the plugin initialization errors out-of-the-box for opencode users.
Verification
npm run buildnode -e "import('./dist/index.js').then(m=>console.log('ok')).catch(console.error)"ERR_MODULE_NOT_FOUNDdue to the extensionless imports. Now it resolves properly without error.