From 9f6ef2a7006f951a233b2dee7fae7b07762013be Mon Sep 17 00:00:00 2001
From: Remko Popma <remkop@yahoo.com>
Date: Sat, 26 Aug 2023 10:53:06 +0900
Subject: [PATCH] [#2059] ArgGroup fix regression and refine solution
 introduced in [#1848][#2030]

---
 RELEASE-NOTES.md                       |  1 +
 src/main/java/picocli/CommandLine.java | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/RELEASE-NOTES.md b/RELEASE-NOTES.md
index b84da06b8..c475a4966 100644
--- a/RELEASE-NOTES.md
+++ b/RELEASE-NOTES.md
@@ -25,6 +25,7 @@ Artifacts in this release are signed by Remko Popma (6601 E5C0 8DCC BB96).
 * [#2060] Bugfix: Fix positional parameters bug with late-resolved arity variable. Thanks to [daisukeoto](https://github.com/daisukeoto) for raising this.
 * [#2074][#2075] Bugfix: Don't generate auto-complete for hidden attributes in `picocli.shell.jline3.PicoCommand`. Thanks to [clebertsuconic](https://github.com/clebertsuconic) for the pull request.
 * [#2083][#2084] Enhancement: Java 22 update: improve logic for detecting if the output stream is connected to a terminal. Thanks to [Liam Miller-Cushon](https://github.com/cushon) for the pull request.
+* [#2059] Bugfix: ArgGroup with `exclusive=false` and `multiplicity=1` should require at least one option; fix regression and refine solution introduced in [#1848][#2030].  Thanks to [Utkarsh Mittal](https://github.com/utmittal) for raising this.
 * [#2080] DOC: Improve GraalVM documentation: add `graalvm-native-image-plugin`. Thanks to [Bhavik Patel](https://github.com/bhavikp19) for the pull request.
 
 ## <a name="4.7.5-deprecated"></a> Deprecations
diff --git a/src/main/java/picocli/CommandLine.java b/src/main/java/picocli/CommandLine.java
index cd20ede00..1b721f2f7 100644
--- a/src/main/java/picocli/CommandLine.java
+++ b/src/main/java/picocli/CommandLine.java
@@ -13028,8 +13028,27 @@ void validate(CommandLine commandLine) {
                 }
             }
 
-            private boolean containsRequiredOptionsOrSubgroups(ArgGroupSpec argGroupSpec) {
-                return containsRequiredOptionsOrParameters(argGroupSpec) || containsRequiredSubgroups(argGroupSpec);
+            /**
+             * A group is optional if <ul>
+             * <li>its minimum <code>multiplicity</code> is zero</li>
+             * <li>otherwise, if the group has at least one required option and all required options have default values</li>
+             * </ul>
+             *
+             * Conversely, a group is required if <ul>
+             * <li>if its minimum <code>multiplicity</code> is <code>1</code> or more <em>AND</em></li>
+             * <li>
+             *   <ul>
+             *     <li>either the group has no required options</li>
+             *     <li>or the group has at least one required option without a default value</li>
+             *   </ul>
+             * </li>
+             * </ul>
+             * @see <a href="https://github.com/remkop/picocli/issues/1848">https://github.com/remkop/picocli/issues/1848</a>
+             *  and <a href="https://github.com/remkop/picocli/issues/2059">https://github.com/remkop/picocli/issues/2059</a>
+             */
+            private boolean isGroupEffectivelyOptional(ArgGroupSpec argGroupSpec) {
+                if (argGroupSpec.multiplicity().min == 0) {return true; }
+                return requiredOptionsExistAndAllHaveDefaultValues(argGroupSpec) && !containsRequiredSubgroups(argGroupSpec);
             }
 
             private boolean containsRequiredOptionsOrParameters(ArgGroupSpec argGroupSpec) {