wp-env: better run command errors (#22475)

Fixes issues noticed in #21537 (comment).

packages/env/lib/cli.js

@@ -40,6 +40,8 @@ const withSpinner = ( command ) => ( ...args ) => {
 				spinner.fail( error.message );
 				process.exit( 1 );
 			} else if (
+				error &&
+				typeof error === 'object' &&
 				'exitCode' in error &&
 				'err' in error &&
 				'out' in error
@@ -54,13 +56,18 @@ const withSpinner = ( command ) => ( ...args ) => {
 					process.stderr.write( error.err );
 				}
 				process.exit( error.exitCode );
-			} else {
+			} else if ( error ) {
 				// Error is an unknown error. That means there was a bug in our code.
-				spinner.fail( error.message );
+				spinner.fail(
+					typeof error === 'string' ? error : error.message
+				);
 				// Disable reason: Using console.error() means we get a stack trace.
 				// eslint-disable-next-line no-console
 				console.error( error );
 				process.exit( 1 );
+			} else {
+				spinner.fail( 'An unknown error occured.' );
+				process.exit( 1 );
 			}
 		}
 	);

packages/env/lib/commands/run.js

@@ -40,7 +40,13 @@ module.exports = async function run( { container, command, spinner, debug } ) {
 		console.error(
 			process.stdout.isTTY ? `\n\n${ result.err }\n\n` : result.err
 		);
-		throw result.err;
+		// Some tools (like composer) may send messages to stderr. Those messages
+		// do not always mean that we need to abort the process. For example,
+		// composer will say "Nothing to install or update" on stderr when your
+		// local composer packages are up to date.
+		if ( result.exitCode !== 0 ) {
+			throw result.err;
+		}
 	}
 
 	spinner.text = `Ran \`${ command }\` in '${ container }'.`;