Refactor tier 3 target validation: move logic to ensureInstalledTargets and simplify getInstalledTargets

Co-authored-by: kraenhansen <1243959+kraenhansen@users.noreply.github.com>

Author: Copilot

packages/ferric/src/rustup.ts

@@ -2,18 +2,28 @@ import cp from "node:child_process";
 
 import { UsageError } from "@react-native-node-api/cli-utils";
 
-/**
- * Tier 3 targets that require build-std (defined here to avoid circular imports)
- */
-const TIER_3_TARGETS = [
-  "aarch64-apple-visionos",
-  "aarch64-apple-visionos-sim",
-] as const;
+export function getInstalledTargets() {
+  try {
+    return new Set(
+      cp
+        .execFileSync("rustup", ["target", "list", "--installed"], {
+          encoding: "utf-8",
+        })
+        .split("\n")
+        .filter((line) => line.trim() !== ""),
+    );
+  } catch (error) {
+    throw new UsageError(
+      "You need a Rust toolchain: https://doc.rust-lang.org/cargo/getting-started/installation.html#install-rust-and-cargo",
+      { cause: error },
+    );
+  }
+}
 
 /**
- * Check if nightly Rust with rust-src component is available for build-std
+ * Check if build-std prerequisites are available for tier 3 targets
  */
-function isBuildStdAvailable(): boolean {
+export function isBuildStdAvailable(): boolean {
   try {
     // Check if nightly toolchain is available
     const toolchains = cp.execFileSync("rustup", ["toolchain", "list"], {
@@ -34,30 +44,3 @@ function isBuildStdAvailable(): boolean {
     return false;
   }
 }
-
-export function getInstalledTargets() {
-  try {
-    const installedTargets = new Set(
-      cp
-        .execFileSync("rustup", ["target", "list", "--installed"], {
-          encoding: "utf-8",
-        })
-        .split("\n")
-        .filter((line) => line.trim() !== ""),
-    );
-
-    // Add tier 3 targets if build-std is properly configured
-    if (isBuildStdAvailable()) {
-      for (const target of TIER_3_TARGETS) {
-        installedTargets.add(target);
-      }
-    }
-
-    return installedTargets;
-  } catch (error) {
-    throw new UsageError(
-      "You need a Rust toolchain: https://doc.rust-lang.org/cargo/getting-started/installation.html#install-rust-and-cargo",
-      { cause: error },
-    );
-  }
-}

packages/ferric/src/targets.ts

@@ -1,5 +1,5 @@
 import { chalk, UsageError, assertFixable } from "@react-native-node-api/cli-utils";
-import { getInstalledTargets } from "./rustup.js";
+import { getInstalledTargets, isBuildStdAvailable } from "./rustup.js";
 
 export const ANDROID_TARGETS = [
   "aarch64-linux-android",
@@ -69,7 +69,7 @@ export function isTier3Target(target: TargetName): boolean {
 }
 
 /**
- * Ensure the targets are installed into the Rust toolchain
+ * Ensure the targets are available for building
  * We do this up-front because the error message and fix is very unclear from the failure when missing.
  */
 export function ensureInstalledTargets(expectedTargets: Set<TargetName>) {
@@ -93,29 +93,27 @@ export function ensureInstalledTargets(expectedTargets: Set<TargetName>) {
   );
 
   // Handle tier 3 targets that require build-std setup
-  // Check if tier 3 targets are properly configured (included in installedTargets means they're available)
-  const missingTier3Targets = new Set([
-    ...[...tier3Targets].filter((target) => !installedTargets.has(target)),
-  ]);
-
-  assertFixable(
-    missingTier3Targets.size === 0,
-    `You're using tier 3 targets (${[...missingTier3Targets].join(", ")}) that require building the standard library from source`,
-    {
-      instructions:
-        `To set up support for these targets:\n\n` +
-        `1. Install nightly Rust with the rust-src component:\n` +
-        `   ${chalk.italic("rustup toolchain install nightly --component rust-src")}\n\n` +
-        `2. Configure Cargo to use build-std by creating a .cargo/config.toml file:\n` +
-        `   ${chalk.italic("[unstable]")}\n` +
-        `   ${chalk.italic('build-std = ["std", "panic_abort"]')}\n\n` +
-        `3. Set your default toolchain to nightly:\n` +
-        `   ${chalk.italic("rustup default nightly")}\n\n` +
-        `For more information, see:\n` +
-        `- Rust Platform Support: ${chalk.italic("https://doc.rust-lang.org/rustc/platform-support.html")}\n` +
-        `- Cargo build-std: ${chalk.italic("https://doc.rust-lang.org/cargo/reference/unstable.html#build-std")}`,
-    },
-  );
+  if (tier3Targets.size > 0) {
+    // For tier 3 targets, check if build-std prerequisites are met
+    assertFixable(
+      isBuildStdAvailable(),
+      `You're using tier 3 targets (${[...tier3Targets].join(", ")}) that require building the standard library from source`,
+      {
+        instructions:
+          `To set up support for these targets:\n\n` +
+          `1. Install nightly Rust with the rust-src component:\n` +
+          `   ${chalk.italic("rustup toolchain install nightly --component rust-src")}\n\n` +
+          `2. Configure Cargo to use build-std by creating a .cargo/config.toml file:\n` +
+          `   ${chalk.italic("[unstable]")}\n` +
+          `   ${chalk.italic('build-std = ["std", "panic_abort"]')}\n\n` +
+          `3. Set your default toolchain to nightly:\n` +
+          `   ${chalk.italic("rustup default nightly")}\n\n` +
+          `For more information, see:\n` +
+          `- Rust Platform Support: ${chalk.italic("https://doc.rust-lang.org/rustc/platform-support.html")}\n` +
+          `- Cargo build-std: ${chalk.italic("https://doc.rust-lang.org/cargo/reference/unstable.html#build-std")}`,
+      },
+    );
+  }
 }
 
 export function isAndroidTarget(