Add error message from subcommands

src/normalize.ts

@@ -49,10 +49,23 @@ export class ProjectNormalizer {
     );
   }
 
+  async run(...cmd: string[]): Promise<string> {
+    const p = this.sys.run({ cmd, stdout: "piped", stderr: "piped" });
+    const [status, stdout, stderr] = await Promise.all([
+      p.status(),
+      p.output(),
+      p.stderrOutput(),
+    ]);
+    if (status.success) {
+      return new TextDecoder().decode(stdout);
+    } else {
+      console.error(new TextDecoder().decode(stderr));
+      throw new Error(`Command failed: ${cmd.join(" ")}`);
+    }
+  }
+
   async formatPath(path: string) {
-    await this.sys.run({
-      cmd: ["./run", "fmt", "-q", path],
-    }).status();
+    await this.run("./run", "fmt", "-q", path);
   }
 
   async updateRunScript() {
@@ -84,11 +97,7 @@ export class ProjectNormalizer {
   }
 
   async updateDenoDefs() {
-    const process = this.sys.run({
-      cmd: ["./run", "types"],
-      stdout: "piped",
-    });
-    const defs = new TextDecoder("utf-8").decode(await process.output());
+    const defs = await this.run("./run", "types");
     await this.sys.writeTextFile("deno.d.ts", defs);
   }