fix: preprocess error reporting

[dominikg]

see #259

include stack and filename in errors thrown from svelte.preprocess

This should give people enough information to track it down. new output looks like this

Error while preprocessing /home/dominikg/develop/sveltejs/vite-plugin-svelte/packages/playground/kit-demo-ts/src/routes/__layout.svelte - Cannot read properties of undefined (reading 'split')
TypeError: Error while preprocessing /home/dominikg/develop/sveltejs/vite-plugin-svelte/packages/playground/kit-demo-ts/src/routes/__layout.svelte - Cannot read properties of undefined (reading 'split')
    at Object.parseAttributes (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/modules/markup.js:19:10)
    at getScriptContent (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/transformers/typescript.js:47:38)
    at injectVarsToCode (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/transformers/typescript.js:83:20)
    at mixedImportsTranspiler (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/transformers/typescript.js:205:26)
    at transformer (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/transformers/typescript.js:275:11)
    at Object.exports.transform (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/autoProcess.js:37:12)
    at async /home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/autoProcess.js:113:29
    at async script (/home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte-preprocess@4.9.0_svelte@3.46.2+typescript@4.5.5/node_modules/svelte-preprocess/dist/autoProcess.js:143:33)
    at async process_single_tag (file:///home/dominikg/develop/sveltejs/vite-plugin-svelte/node_modules/.pnpm/svelte@3.46.2/node_modules/svelte/compiler.mjs:32106:27)
    at async Promise.all (index 0)

Note: stack is omitted during dev for errors that include a code frame unless DEBUG environment variable is set. This is done to keep the noise down for compiler errors. The stack is huge and spammy and not nearly as helpful as the frame and message, in most cases.

[dominikg]

@benmccann i think this is be best we can do from vite-plugin-svelte's side. For more information, svelte.preprocess or the preprocessor itself would have to add it to the error.

The stacktrace should give a pretty good idea of which preprocessor is at fault and the filename of the file it broke should help in reporting it to that.

[benmccann]

This is way better. Thank you!