From 839ed2588c403a18b9f9db8cb7940a74f19a280e Mon Sep 17 00:00:00 2001
From: CreepySkeleton <creepy-skeleton@yandex.ru>
Date: Tue, 3 Mar 2020 22:00:35 +0300
Subject: [PATCH] Fix core dump with mutually `requires()` args

Fixes #1643
---
 src/build/app/mod.rs |  7 +++++++
 tests/require.rs     | 27 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/build/app/mod.rs b/src/build/app/mod.rs
index 7d73af7d..1b67908d 100644
--- a/src/build/app/mod.rs
+++ b/src/build/app/mod.rs
@@ -1922,10 +1922,17 @@ impl<'b> App<'b> {
             }
         };
 
+        let mut processed = vec![];
         let mut r_vec = vec![arg];
         let mut args = vec![];
 
         while let Some(a) = r_vec.pop() {
+            if processed.contains(&a) {
+                continue;
+            }
+
+            processed.push(a);
+
             if let Some(arg) = self.find(a) {
                 if let Some(ref reqs) = arg.requires {
                     for r in reqs.iter().filter_map(requires_if_or_not) {
diff --git a/tests/require.rs b/tests/require.rs
index 0da7bbf9..1589fb92 100644
--- a/tests/require.rs
+++ b/tests/require.rs
@@ -703,3 +703,30 @@ fn issue_1158_conflicting_requirements_rev() {
 
     assert!(res.is_ok());
 }
+
+#[test]
+fn issue_1643_args_mutually_require_each_other() {
+    use clap::*;
+
+    fn main() {
+        let app = App::new("test")
+            .arg(
+                Arg::with_name("relation_id")
+                    .help("The relation id to get the data from")
+                    .long("relation-id")
+                    .short('r')
+                    .takes_value(true)
+                    .requires("remote_unit_name"),
+            )
+            .arg(
+                Arg::with_name("remote_unit_name")
+                    .help("The name of the remote unit to get data from")
+                    .long("remote-unit")
+                    .short('u')
+                    .takes_value(true)
+                    .requires("relation_id"),
+            );
+
+        app.get_matches_from(&["test", "-u", "hello"]);
+    }
+}