From f10c1d267bbddbf289c23d4955c70e1a2d2710eb Mon Sep 17 00:00:00 2001
From: Nikita Kniazev <nok.raven@gmail.com>
Date: Wed, 15 Dec 2021 16:21:35 +0300
Subject: [PATCH] Improve dependency cycle diagnostic message (#114)

Before:
```
error: ./forward ./stage ./stage-proper libs/filesystem/build/stage libs/filesystem/build/stage-dependencies libs/log/build/stage libs/log/build/stage-dependencies libs/filesystem/build/stage
```

After:
```
error: ./forward -> ./stage -> ./stage-proper -> ***libs/filesystem/build/stage*** -> libs/filesystem/build/stage-dependencies -> libs/log/build/stage -> libs/log/build/stage-dependencies -> ***libs/filesystem/build/stage***
```
---
 src/build/targets.jam | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/build/targets.jam b/src/build/targets.jam
index ba575235a..dfbd7a1d4 100644
--- a/src/build/targets.jam
+++ b/src/build/targets.jam
@@ -600,13 +600,21 @@ local rule start-building ( main-target-instance )
         local names ;
         for local t in $(.targets-being-built) $(main-target-instance)
         {
-            names += [ $(t).full-name ] ;
+            local name = [ $(t).full-name ] ;
+            if $(t) = $(main-target-instance)
+            {
+                names += ***$(name)*** ;
+            }
+            else
+            {
+                names += $(name) ;
+            }
         }
 
         import errors ;
         errors.error "Recursion in main target references"
           : "the following target are being built currently:"
-          : $(names) ;
+          : $(names:J=" -> ") ;
     }
     .targets-being-built += $(main-target-instance) ;
 }