fix: report a null exit code when the process is killed by a signal

src/types.ts

@@ -6,7 +6,7 @@
 export type ArgvOrCommandLine = string[] | string;
 
 export interface IExitEvent {
-  exitCode: number;
+  exitCode: number | null;
   signal: number | undefined;
 }
 

src/unixTerminal.test.ts

@@ -117,12 +117,21 @@ if (process.platform !== 'win32') {
       const term = new UnixTerminal('node');
       it('should exit when terminal is destroyed programmatically', (done) => {
         term.on('exit', (code, signal) => {
-          assert.strictEqual(code, 0);
+          assert.strictEqual(code, null);
           assert.strictEqual(signal, constants.signals.SIGHUP);
           done();
         });
         term.destroy();
       });
+      it('should report a null exit code when killed by a signal', (done) => {
+        const killed = new UnixTerminal('node');
+        killed.onExit(({ exitCode, signal }) => {
+          assert.strictEqual(exitCode, null);
+          assert.strictEqual(signal, constants.signals.SIGKILL);
+          done();
+        });
+        killed.kill('SIGKILL');
+      });
     });
     describe('signals in parent and child', () => {
       it('SIGINT - custom in parent and child', done => {

src/unixTerminal.ts

@@ -75,7 +75,10 @@ export class UnixTerminal extends Terminal {
 
     const encoding = (opt.encoding === undefined ? 'utf8' : opt.encoding);
 
-    const onexit = (code: number, signal: number): void => {
+    const onexit = (rawCode: number, signal: number): void => {
+      // Align with child_process: a process terminated by a signal has no
+      // exit code, so report null instead of a misleading 0.
+      const code = signal ? null : rawCode;
       // XXX Sometimes a data event is emitted after exit. Wait til socket is
       // destroyed.
       if (!this._emittedClose) {

typings/node-pty.d.ts

@@ -151,9 +151,11 @@ declare module 'node-pty' {
 
     /**
      * Adds an event listener for when an exit event fires. This happens when the pty exits.
+     * On Unix, `exitCode` is `null` when the process was terminated by a signal, in which case
+     * `signal` holds the signal number.
      * @returns an `IDisposable` to stop listening.
      */
-    readonly onExit: IEvent<{ exitCode: number, signal?: number }>;
+    readonly onExit: IEvent<{ exitCode: number | null, signal?: number }>;
 
     /**
      * Resizes the dimensions of the pty.