feature: adding 'listen' option to restrict binding of interfaces

lib/cli/cli-options.ts

@@ -53,6 +53,7 @@ export function merge(input) {
         appendServerDirectoryOption,
         handleProxyOption,
         handlePortsOption,
+        handleHostOption,
         handleGhostModeOption,
         handleFilesOption,
         handleExtensionsOption,

lib/cli/transforms/handleHostOption.ts

@@ -0,0 +1,35 @@
+import {BsTempOptions, TransformResult} from "../cli-options";
+import {BsErrorLevels, BsErrorTypes} from "../../bin";
+
+export function handleHostOption(incoming: BsTempOptions): TransformResult {
+    const host: string|null = incoming.get("host");
+    const listen: string|null = incoming.get("listen");
+
+    if (host && listen) {
+        if (host !== listen) {
+            return [incoming, [{
+                errors: [
+                    {
+                        error: new Error("Cannot specify both `host` and `listen` options"),
+                        meta() {
+                            return [
+                                "",
+                                "Tip:           Use just the `listen` option *only* if you want to bind only to a particular host.",
+                            ]
+                        }
+                    }
+                ],
+                level: BsErrorLevels.Fatal,
+                type: BsErrorTypes.HostAndListenIncompatible
+            }]];
+        }
+
+        // whenever we have have both `host` + `listen` options,
+        // we remove the 'host' to prevent complication further down the line
+        return [
+            incoming.delete('host'),
+        []];
+    }
+
+    return [incoming, []];
+}