From 7a24cd528f56a6ee3b8c16527eb4e68eca5eb901 Mon Sep 17 00:00:00 2001
From: Zefir Kirilov <contact@zefir.pro>
Date: Wed, 26 Nov 2025 11:53:46 +0200
Subject: [PATCH] Refine parser error messages for flags given `=` values
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This PR improves the clarity of argument parser messages when a boolean
flag is incorrectly provided with a value using `=`.

Previously, cases like `-f=val` or `--flag=value` would produce
misleading messages such as ‘unknown option '-f'’ even if the flag
exists. Now, the parser reports more precise messages:

- `unexpected '=' for option '-f'`
- `unexpected '=' for option '--flag'`
- `unexpected '=' in combined short options '-ff'`
---
 src/cmd/command.d | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/cmd/command.d b/src/cmd/command.d
index ffaca0e..1212df0 100644
--- a/src/cmd/command.d
+++ b/src/cmd/command.d
@@ -330,9 +330,12 @@ public class Command {
                     exit(program.printVersion());
                 if (program.helpOption() !is null && program.helpOption().matches(arg))
                     exit(printHelp());
+                    
+                const auto equalsIndex = arg.indexOf('=');
+                const string optName = equalsIndex >= 0 ? arg[0..equalsIndex] : arg;
 
-                if (arg.length > 2 && arg[0] == '-' && arg[1] != '-' && arg[2] != '=') {
-                    foreach (c; arg[1 .. $]) {
+                if (optName.length > 2 && optName[0] == '-' && optName[1] != '-') {
+                    foreach (c; optName[1..$]) {
                         const shortArg = "-" ~ c;
                         const(Flag) f = findFlag(shortArg);
                         if (f !is null) {
@@ -344,17 +347,19 @@ public class Command {
                             error("missing value for option '" ~ shortArg ~ "'", 2);
                         program.error("unknown option '" ~ shortArg ~ "'", 2);
                     }
+                    if (equalsIndex >= 0)
+                        error("unexpected '=' in combined short options '" ~ optName ~ "'", 2);
                     continue;
                 }
 
-                const(Flag) flag = findFlag(arg);
+                const(Flag) flag = findFlag(optName);
                 if (flag !is null) {
+                    if (equalsIndex >= 0)
+                        error("unexpected '=' for option '" ~ optName ~ "'", 2);
                     parsedFlags[flag] = parsedFlags.get(flag, 0) + 1;
                     continue;
                 }
 
-                const auto equalsIndex = arg.indexOf('=');
-                const string optName = equalsIndex >= 0 ? arg[0..equalsIndex] : arg;
                 const(Option) option = findOption(optName);
                 if (option !is null) {
                     string value;