From 708c4a61b1a778744d0442988eb6659ae2697f0a Mon Sep 17 00:00:00 2001
From: Luca Toniolo <10792599+grandixximo@users.noreply.github.com>
Date: Mon, 9 Nov 2026 17:03:30 +1100
Subject: [PATCH] halcmd: warn about an arrow written against a name

"net lube-pump=> io.relay5" makes a signal named "lube-pump=>", since
halcmd only drops an arrow that stands as its own word. The config
loads, and the odd name only shows up later, when halcmd commands
typed by hand cannot find the signal.

net, linkps and linksp now warn about an argument that starts or ends
with "=>" or "<=". A name with an arrow in the middle, like "in=>out",
stays silent and still works.

The linkps help text listed the arrows as '==>' and '<=='; halcmd
drops only '=>', '<=' and '<=>', and takes '==>' as a name.

Reported by dirkx in #4645.
---
 docs/src/man/man1/halcmd.1.adoc  |  5 ++++-
 src/hal/utils/halcmd.c           | 12 ++++++++++++
 src/hal/utils/halcmd_commands.cc |  2 +-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/docs/src/man/man1/halcmd.1.adoc b/docs/src/man/man1/halcmd.1.adoc
index 82a8b2369f5..a8baf1d5162 100644
--- a/docs/src/man/man1/halcmd.1.adoc
+++ b/docs/src/man/man1/halcmd.1.adoc
@@ -144,7 +144,10 @@ requested component with a call to *dlopen(3)*.
   _arrow_ can be "`=>`", "`<=`", "`<=>`", or omitted. *halcmd* ignores
   arrows, but they can be useful in command files to document the
   direction of data flow. Arrows should not be used on the command line
-  since the shell might try to interpret them. Fails if either _pinname_
+  since the shell might try to interpret them. An arrow is only an arrow
+  when spaces separate it from the names: "`lube-pump=>`" is a signal
+  name, and *halcmd* warns about a name that starts or ends with an
+  arrow. Fails if either _pinname_
   or _signame_ does not exist, or if they are not the same type type.
 *linksp* _signame_ [_arrow_] _pinname_::
   (OBSOLETE - use *net* instead) (_link_ __s__ignal to __p__in) Works
diff --git a/src/hal/utils/halcmd.c b/src/hal/utils/halcmd.c
index 694801c8d0a..d27824ad053 100644
--- a/src/hal/utils/halcmd.c
+++ b/src/hal/utils/halcmd.c
@@ -303,6 +303,14 @@ static int count_args(const char **argv) {
     return i;
 }
 
+/* "lube-pump=>" or "=>io.relay": an arrow written without a space */
+static int has_attached_arrow(const char *arg) {
+    size_t len = strlen(arg);
+    if(len < 3) return 0;
+    return !strncmp(arg, "<=", 2) || !strncmp(arg, "=>", 2) ||
+	   !strcmp(arg + len - 2, "<=") || !strcmp(arg + len - 2, "=>");
+}
+
 #define ARG(i) (argc > i ? argv[i] : NULL)
 #define REST(i) (argc > i ? argv + i : argv + argc)
 
@@ -338,6 +346,10 @@ static int parse_cmd1(const char **argv) {
 		   !strcmp(argv[s], "<=>")) {
 		    continue;
 		} else {
+		    if(has_attached_arrow(argv[s]))
+			halcmd_warning("'%s' has an arrow attached, it is taken"
+			    " as part of the name; put a space between the name"
+			    " and the arrow\n", argv[s]);
 		    argv[d++] = argv[s];
 		}
 	    }
diff --git a/src/hal/utils/halcmd_commands.cc b/src/hal/utils/halcmd_commands.cc
index 35241919828..3252cb920e0 100644
--- a/src/hal/utils/halcmd_commands.cc
+++ b/src/hal/utils/halcmd_commands.cc
@@ -2517,7 +2517,7 @@ int do_help_cmd(const char *command)
 	printf("linksp signame [arrow] pinname\n");
 	printf("  Links pin 'pinname' to signal 'signame'.  Both forms do\n");
 	printf("  the same thing.  Use whichever makes sense.  The optional\n");
-	printf("  'arrow' can be '==>', '<==', or '<=>' and is ignored.  It\n");
+	printf("  'arrow' can be '=>', '<=', or '<=>' and is ignored.  It\n");
 	printf("  can be used in files to show the direction of data flow,\n");
 	printf("  but don't use arrows on the command line.\n");
     } else if(strcmp(command, "net") == 0) {