Is it possible to preserve unused imports that aren't types?

[ryanatkn]

Question

In upgrading from 1.2.28 to 1.2.35 I'm running into a problem for my use case which requires unused imports to be preserved. This seems to have changed with the import stripping functionality in PRs #1060 and #1101. I looked through the docs, issues/PRs, and briefly the code (I know only a little Rust), and couldn't find an answer - sorry if it's obvious. :)

Is import_not_used_as_values/strip::ImportNotUsedAsValues exposed as an option? I was unable to figure out how to test with different values.

My use case is using swc to preprocess the TypeScript in Svelte files. Svelte combines JS/TS with an HTML-like templating language in the same file, so imports are often not referenced in the code given to swc. The behavior in 1.2.28 has worked for what I need, except sometimes I've had to use import type.

Thank you! I really love this project.

[intrnl]

+1 for this, but some additional notes.

I'm not sure importsNotUsedAsValues will do the option you think it will do, I also got myself confused. It'll still strip the named imports, leaving only import "abc" for the side effect. I've tested this with tsc and esbuild.

$ echo "import { a, b } from 'module'" | esbuild --loader=ts

$ echo "import { a, b } from 'module'" | esbuild --loader=ts --tsconfig-raw='{"compilerOptions":{"importsNotUsedAsValues":"preserve"}}'
import "module";

Personally, I think that it'd be better to enforce the use of import type for importing types, as we can just strip that off immediately. We could take something like onlyRemoveTypeImports from Babel TypeScript plugin as the option name.

It would be great to have something that can quickly strip off the types for stuff like TypeScript in Svelte templates 👍

[kdy1]

This is fixed by #1318

[btakita]

Thank you for the project. Is there any documentation on how to activate this feature? Is there a onlyRemoveTypeImports or similar config option somewhere?

[kdy1]

@btakita No, currently this is only for rust users.

[btakita]

@ryanatkn, I'm also attempting to compile ts from svelte components. Did you solve this problem using swc? Here is my typescript function to override svelte-preprocess;

async typescript({ content, filename }) {
	const ast = await parse(content, {
		syntax: 'typescript', target: 'es2020'
	})
	const expression_statement_set = new Set<string>()
	for (const statement of ast.body) {
		if (statement.type === 'ImportDeclaration' && (statement as any).typeOnly === false) {
			for (const specifier of statement.specifiers) {
				if (specifier.type === 'ImportDefaultSpecifier' || specifier.type === 'ImportSpecifier') {
					expression_statement_set.add(specifier.local.value)
				}
			}
		}
	}
	const expression_statement_a = [...expression_statement_set]
	if (expression_statement_a.length) {
		const expression_statement = `${expression_statement_a.join(', ')};`
		const { code } = await transform(`${content}\n${expression_statement}`, swc_plugin_options)
		return {
			code: code.replace(`\n${expression_statement}`, ''), filename
		}
	} else {
		const { code } = await transform(content, swc_plugin_options)
		return {
			code, filename
		}
	}
}

[ryanatkn]

@btakita I didn't solve this, I'm using the import type workaround and the tsconfig option importsNotUsedAsValues -- sveltejs/svelte-preprocess#206

[swc-bot]

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