From 0be886fac188c4127bf5bc38f8c82f338c73cdcc Mon Sep 17 00:00:00 2001
From: Fabian Freyer <fabian.freyer@physik.tu-berlin.de>
Date: Mon, 15 May 2023 20:26:44 +0200
Subject: [PATCH] fix(help): Render partially optional values with []

Fixes: #4847
---
 clap_builder/src/builder/arg.rs | 16 ++++++++++++++--
 tests/builder/help.rs           | 21 +++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/clap_builder/src/builder/arg.rs b/clap_builder/src/builder/arg.rs
index ddd4418499b3..f327d560d59c 100644
--- a/clap_builder/src/builder/arg.rs
+++ b/clap_builder/src/builder/arg.rs
@@ -4363,8 +4363,20 @@ impl Arg {
         }
 
         debug_assert!(self.is_takes_value_set());
+
         for (n, val_name) in val_names.iter().enumerate() {
-            let arg_name = if self.is_positional() && (num_vals.min_values() == 0 || !required) {
+            let value_is_required = match self.is_positional() {
+                true => required && (num_vals.min_values() != 0),
+                false => {
+                    // If all values are optional, the [] get rendered by the caller:
+                    //    --foo[=<bar>]
+                    // In this case, treat as required.
+                    let required = self.get_min_vals() == 0;
+                    required || (n < num_vals.min_values())
+                }
+            };
+
+            let arg_name = if !value_is_required {
                 format!("[{val_name}]")
             } else {
                 format!("<{val_name}>")
@@ -4646,7 +4658,7 @@ mod test {
             .value_names(["file", "name"]);
         o._build();
 
-        assert_eq!(o.to_string(), "-o <file> <name>...");
+        assert_eq!(o.to_string(), "-o <file> [name]...");
     }
 
     #[test]
diff --git a/tests/builder/help.rs b/tests/builder/help.rs
index 526bc0c6e4dd..84eaf9778642 100644
--- a/tests/builder/help.rs
+++ b/tests/builder/help.rs
@@ -2845,3 +2845,24 @@ fn display_name_subcommand_explicit() {
         Some("child.display")
     );
 }
+
+#[test]
+fn issue_4847_usage() {
+    static USAGE_WITH_GROUP: &str = "\
+Usage: deno [OPTIONS]
+
+Options:
+      --example <REQUIRED> [OPTIONAL]  issue 4847
+  -h, --help                           Print help
+";
+
+    let cmd = clap::Command::new("hello").bin_name("deno").arg(
+        Arg::new("example")
+            .long("example")
+            .num_args(1..=2)
+            .help("issue 4847")
+            .value_names(&["REQUIRED", "OPTIONAL"]),
+    );
+
+    utils::assert_output(cmd, "deno --help", USAGE_WITH_GROUP, false);
+}