fix(cli): allow setting of importsNotUsedAsValues in Deno.compile() (#…

…8306)

Fixes #6663

cli/dts/lib.deno.unstable.d.ts

@@ -318,6 +318,20 @@ declare namespace Deno {
     /** Import emit helpers (e.g. `__extends`, `__rest`, etc..) from
      * [tslib](https://www.npmjs.com/package/tslib). */
     importHelpers?: boolean;
+    /** This flag controls how `import` works, there are 3 different options:
+     * 
+     * - `remove`: The default behavior of dropping import statements which only
+     *   reference types.
+     * - `preserve`: Preserves all `import` statements whose values or types are
+     *   never used. This can cause imports/side-effects to be preserved.
+     * - `error`: This preserves all imports (the same as the preserve option),
+     *   but will error when a value import is only used as a type. This might
+     *   be useful if you want to ensure no values are being accidentally
+     *   imported, but still make side-effect imports explicit.
+     * 
+     * This flag works because you can use `import type` to explicitly create an
+     * `import` statement which should never be emitted into JavaScript. */
+    importsNotUsedAsValues?: "remove" | "preserve" | "error";
     /** Emit a single file with source maps instead of having a separate file.
      * Defaults to `false`. */
     inlineSourceMap?: boolean;

cli/tests/compiler_api_test.ts

@@ -199,3 +199,24 @@ Deno.test({
     });
   },
 });
+
+Deno.test({
+  name: `Deno.compile() - Allows setting of "importsNotUsedAsValues"`,
+  async fn() {
+    const [diagnostics] = await Deno.compile("/a.ts", {
+      "/a.ts": `import { B } from "./b.ts";
+        const b: B = { b: "b" };
+      `,
+      "/b.ts": `export interface B {
+        b: string;
+      };
+      `,
+    }, {
+      importsNotUsedAsValues: "error",
+    });
+    assert(diagnostics);
+    assertEquals(diagnostics.length, 1);
+    assert(diagnostics[0].messageText);
+    assert(diagnostics[0].messageText.includes("This import is never used"));
+  },
+});