Surface run:command stderr and fail fast on command errors

src/lib/plugins/run-code-blocks/directives/command.ts

@@ -17,6 +17,15 @@ interface Args {
   captureOutput?: boolean;
 }
 
+interface CommandError {
+  stdout?: string;
+  stderr?: string;
+}
+
+function isCommandError(error: unknown): error is CommandError {
+  return typeof error === 'object' && error !== null && ('stdout' in error || 'stderr' in error);
+}
+
 export default async function command(node: Code, options: Options): Promise<Option<Code>> {
   let args = parseArgs<Args>(node, [
     optional('lang', String, 'shell'),
@@ -52,13 +61,38 @@ export default async function command(node: Code, options: Options): Promise<Opt
       output.push(`$ ${display}`);
     }
 
-    let { stdout } = await exec(cmd, { cwd });
+    try {
+      let { stdout, stderr } = await exec(cmd, { cwd });
 
-    if (args.captureOutput) {
-      output.push(stdout);
-    }
+      if (args.captureOutput) {
+        if (stdout) {
+          output.push(stdout);
+        }
 
-    console.log(stdout)
+        if (stderr) {
+          output.push(stderr);
+        }
+      }
+
+      console.log(stdout);
+      if (stderr) {
+        console.error(stderr);
+      }
+    } catch (error) {
+      if (args.captureOutput && isCommandError(error)) {
+        let { stdout, stderr } = error;
+
+        if (stdout) {
+          output.push(stdout);
+        }
+
+        if (stderr) {
+          output.push(stderr);
+        }
+      }
+
+      throw error;
+    }
   }
 
   if (args.hidden) {