chore: preserve generated files in sdk output

packages/backend/toolchain/sdk/generate.ts

@@ -1,6 +1,6 @@
 import { exists, move } from "@std/fs";
 import { resolve } from "@std/path";
-import { CommandError, UnreachableError } from "../error/mod.ts";
+import { UnreachableError } from "../error/mod.ts";
 import { Project } from "../project/mod.ts";
 import { projectDataPath, SDK_PATH } from "../project/project.ts";
 import { progress, success } from "../term/status.ts";
@@ -9,23 +9,20 @@ import { generateTypescript } from "./typescript/mod.ts";
 import { generateUnity } from "./unity/mod.ts";
 import { generateGodot } from "./godot/mod.ts";
 import { SdkConfig } from "../config/project.ts";
-import { unimplemented } from "@std/assert";
 
 export enum SdkTarget {
 	TypeScript = "typescript",
 	Unity = "unity",
 	Godot = "godot",
 }
 
-interface Generator {
-}
-
 export async function generateSdk(
 	project: Project,
 	sdk: SdkConfig,
 ) {
 	const targetString = targetToString(sdk.target);
 	const sdkGenPath = resolve(projectDataPath(project, SDK_PATH), targetString);
+  const sdkOutput = resolve(Deno.cwd(), sdk.output);
 
 	// Clear artifacts
 	try {
@@ -38,21 +35,52 @@ export async function generateSdk(
 
 	progress("Building SDK", targetString);
 
-	let sdkCopyPath = sdkGenPath;
+  // Generate files
+  //
+  // preservePaths is used for preserving generated artifacts from things like
+  // `npm install`.
+  let preservePaths: string[];
 	if (sdk.target == SdkTarget.TypeScript) {
+    preservePaths = ["dist"];
 		await generateTypescript(project, sdkGenPath);
 	} else if (sdk.target == SdkTarget.Unity) {
+    preservePaths = [];
 		await generateUnity(project, sdkGenPath);
 	} else if (sdk.target == SdkTarget.Godot) {
+    preservePaths = [];
 		await generateGodot(project, sdkGenPath);
 	} else {
 		throw new UnreachableError(sdk.target);
 	}
 
-	if (await exists(sdk.output, { isDirectory: true })) {
-		await Deno.remove(sdk.output, { recursive: true });
+  // Delete target dir
+  const preserveTempDir = await Deno.makeTempDir();
+	if (await exists(sdkOutput, { isDirectory: true })) {
+    // Preserve files before deleting the output path
+    for (const path of preservePaths) {
+      const srcPreservePath = resolve(sdkOutput, path);
+      const dstPreservePath = resolve(preserveTempDir, path);
+      if (await exists(srcPreservePath)) {
+        await move(srcPreservePath, dstPreservePath);
+      } else {
+      }
+    }
+
+    // Remove output
+		await Deno.remove(sdkOutput, { recursive: true });
 	}
-	await move(sdkCopyPath, sdk.output, { overwrite: true });
+
+  // Move generated SDK
+	await move(sdkGenPath, sdkOutput, { overwrite: true });
+
+  // Move back preserved files
+  for (const path of preservePaths) {
+    const srcPreservePath = resolve(preserveTempDir, path);
+    const dstPreservePath = resolve(sdkOutput, path);
+    if (await exists(srcPreservePath, { isDirectory: true })) {
+      await move(srcPreservePath, dstPreservePath, { overwrite: false });
+    }
+  }
 
 	success("Success");
 }