fix: use exit code instead of stderr to detect command failures

CLI tools (npm, git, jsr, ping) can write to stderr during normal operation,
causing false errors. Replace `if (stderr) throw stderr` with `throwOnError: true`
from tinyexec, which correctly uses exit codes. Update error checks for EOTP and
ENEEDAUTH to use NonZeroExitError, and add regression tests for stderr tolerance.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: syi0808

src/git.ts

@@ -8,9 +8,7 @@ class GitError extends AbstractError {
 
 export class Git {
   async git(args: string[]): Promise<string> {
-    const { stdout, stderr } = await exec("git", args);
-
-    if (stderr) throw stderr;
+    const { stdout } = await exec("git", args, { throwOnError: true });
 
     return stdout;
   }

src/registry/custom-registry.ts

@@ -4,13 +4,12 @@ import { NpmRegistry } from "./npm.js";
 
 export class CustomRegistry extends NpmRegistry {
   async npm(args: string[]): Promise<string> {
-    const { stdout, stderr } = await exec(
+    const { stdout } = await exec(
       "npm",
       args.concat("--registry", this.registry),
+      { throwOnError: true },
     );
 
-    if (stderr) throw stderr;
-
     return stdout;
   }
 }

src/registry/jsr.ts

@@ -33,9 +33,7 @@ export class JsrRegisry extends Registry {
   }
 
   protected async jsr(args: string[]): Promise<string> {
-    const { stdout, stderr } = await exec("jsr", args);
-
-    if (stderr) throw stderr;
+    const { stdout } = await exec("jsr", args, { throwOnError: true });
 
     return stdout;
   }
@@ -56,13 +54,11 @@ export class JsrRegisry extends Registry {
 
   async ping(): Promise<boolean> {
     try {
-      const { stdout, stderr } = await exec("ping", [
-        new URL(this.registry).hostname,
-        "-c",
-        "1",
-      ]);
-
-      if (stderr) throw stderr;
+      const { stdout } = await exec(
+        "ping",
+        [new URL(this.registry).hostname, "-c", "1"],
+        { throwOnError: true },
+      );
 
       return stdout.includes("1 packets transmitted");
     } catch (error) {

src/registry/npm.ts

@@ -1,4 +1,4 @@
-import { exec } from "tinyexec";
+import { NonZeroExitError, exec } from "tinyexec";
 import { AbstractError } from "../error.js";
 import { getPackageJson } from "../utils/package.js";
 import { isValidPackageName } from "../utils/package-name.js";
@@ -12,9 +12,7 @@ export class NpmRegistry extends Registry {
   registry = "https://registry.npmjs.org";
 
   protected async npm(args: string[]): Promise<string> {
-    const { stdout, stderr } = await exec("npm", args);
-
-    if (stderr) throw stderr;
+    const { stdout } = await exec("npm", args, { throwOnError: true });
 
     return stdout;
   }
@@ -68,7 +66,7 @@ export class NpmRegistry extends Registry {
 
       return true;
     } catch (error) {
-      if (`${error}`.includes("ENEEDAUTH")) {
+      if (error instanceof NonZeroExitError && error.output?.stderr.includes("ENEEDAUTH")) {
         return false;
       }
 
@@ -142,7 +140,7 @@ export class NpmRegistry extends Registry {
       try {
         await this.npm(["publish", "--provenance", "--access", "public"]);
       } catch (error) {
-        if (`${error}`.includes("EOTP")) {
+        if (error instanceof NonZeroExitError && error.output?.stderr.includes("EOTP")) {
           return false;
         }
       }
@@ -166,7 +164,7 @@ export class NpmRegistry extends Registry {
       try {
         await this.npm(args);
       } catch (error) {
-        if (`${error}`.includes("EOTP")) {
+        if (error instanceof NonZeroExitError && error.output?.stderr.includes("EOTP")) {
           return false;
         }
       }

src/tasks/runner.ts

@@ -81,17 +81,9 @@ export async function run(options: ResolvedOptions): Promise<void> {
               task: async (ctx): Promise<void> => {
                 const packageManager = await getPackageManager();
 
-                const { stderr } = await exec(packageManager, [
-                  "run",
-                  ctx.testScript,
-                ]);
-
-                if (stderr) {
-                  throw new AbstractError(
-                    `Failed to run \`${packageManager} run ${ctx.testScript}\``,
-                    { cause: stderr },
-                  );
-                }
+                await exec(packageManager, ["run", ctx.testScript], {
+                  throwOnError: true,
+                });
               },
             },
             {