@swc/wasm-typescript transform mode should no perform import elision

[marco-ippolito]

Describe the bug

Consider this code:

Input code

const { test } = require("node:test");
// replace "../dist/index.js" with "@swc/wasm-typescript" 
const { transformSync } = require("../dist/index.js");
const assert = require("node:assert");

test("should not perform code elision", (t) => {
    const inputCode = `
	import { foo } from ".";
	export { };
  `;
    assert.strictEqual(transformSync(inputCode, { mode: "transform" }).code, "export { };\n");
});

Expected behavior

even if import { foo } from "."; is unused, it should not be removed, since it will change how nodejs handles it.
The same JavaScript code will throw an error.

Actual behavior

unused import is removed

Version

1.7.9

Additional context

No response

[github-actions]

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[magic-akari]

It aligns with TypeScript's behavior, where imports not used as values are considered type imports.
If you wish to retain it, you should activate the verbatimModuleSyntax mode or config ImportsNotUsedAsValues; please refer to this:

swc/crates/swc_fast_ts_strip/src/lib.rs

Lines 40 to 69 in 4b58750

	#[serde(rename_all = "camelCase")]
	pub struct Options {
	#[serde(default)]
	pub module: Option<bool>,
	#[serde(default)]
	pub filename: Option<String>,
	#[serde(default = "default_ts_syntax")]
	pub parser: TsSyntax,
	#[serde(default)]
	pub mode: Mode,
	#[serde(default)]
	pub transform: Option<typescript::Config>,
	#[serde(default)]
	pub source_map: bool,
	}
	#[cfg(feature = "wasm-bindgen")]
	#[wasm_bindgen(typescript_custom_section)]
	const Type_Options: &'static str = r#"
	interface Options {
	module?: boolean;
	filename?: string;
	mode?: Mode;
	sourceMap?: boolean;
	}
	"#;

[magic-akari]

Try this:

const { test } = require("node:test");
const { transformSync } = require("@swc/wasm-typescript");
const assert = require("node:assert");

test("should not perform code elision", (t) => {
    const inputCode = `
	import { foo } from ".";
	export { };
  `;
    assert.strictEqual(
        transformSync(inputCode, {
            mode: "transform",
            transform: {
                verbatimModuleSyntax: true,
            },
        }).code,
        `import { foo } from ".";
export { };
`,
    );
});

test("should preserve import statements with side effects", (t) => {
    const inputCode = `
	import { foo } from ".";
	export { };
  `;
    assert.strictEqual(
        transformSync(inputCode, {
            mode: "transform",
            transform: {
                importNotUsedAsValues: "preserve",
            },
        }).code,
        `import ".";
`,
    );
});