add fallback shell configs

app/session.ts

@@ -11,6 +11,7 @@ import * as config from './config';
 import {cliScriptPath} from './config/paths';
 import {productName, version} from './package.json';
 import {getDecoratedEnv} from './plugins';
+import {getFallBackShellConfig} from './utils/shell-fallback';
 
 const createNodePtyError = () =>
   new Error(
@@ -183,16 +184,16 @@ export default class Session extends EventEmitter {
         // fall back to default shell config if the shell exits within 1 sec with non zero exit code
         // this will inform users in case there are errors in the config instead of instant exit
         const runDuration = new Date().getTime() - this.initTimestamp;
-        if (e.exitCode > 0 && runDuration < 1000) {
+        const fallBackShellConfig = getFallBackShellConfig(shell, shellArgs, defaultShell, defaultShellArgs);
-          const defaultShellConfig = {shell: defaultShell, shellArgs: defaultShellArgs};
+        if (e.exitCode > 0 && runDuration < 1000 && fallBackShellConfig) {
           const msg = `
 shell exited in ${runDuration} ms with exit code ${e.exitCode}
 please check the shell config: ${JSON.stringify({shell, shellArgs}, undefined, 2)}
-fallback to default shell config: ${JSON.stringify(defaultShellConfig, undefined, 2)}
+using fallback shell config: ${JSON.stringify(fallBackShellConfig, undefined, 2)}
 `;
           console.warn(msg);
           this.batcher?.write(msg.replace(/\n/g, '\r\n'));
-          this.init({uid, rows, cols, cwd, ...defaultShellConfig, profile});
+          this.init({uid, rows, cols, cwd, ...fallBackShellConfig, profile});
         } else {
           this.ended = true;
           this.emit('exit');

app/utils/shell-fallback.ts

@@ -0,0 +1,25 @@
+export const getFallBackShellConfig = (
+  shell: string,
+  shellArgs: string[],
+  defaultShell: string,
+  defaultShellArgs: string[]
+): {
+  shell: string;
+  shellArgs: string[];
+} | null => {
+  if (shellArgs.length > 0) {
+    return {
+      shell,
+      shellArgs: []
+    };
+  }
+
+  if (shell != defaultShell) {
+    return {
+      shell: defaultShell,
+      shellArgs: defaultShellArgs
+    };
+  }
+
+  return null;
+};