Show suggestion when Rust build fails

For issue #9

Author: camelpunch

fixtures/example/deps.nix

@@ -61,6 +61,31 @@ let
             ln -s "$lib" "priv/native/$(basename "$lib")"
           done
         '';
+
+        buildPhase = ''
+          suggestion() {
+            echo "***********************************************"
+            echo "                 deps_nix                      "
+            echo
+            echo " Rust dependency build failed.                 "
+            echo
+            echo " If you saw network errors, you might need     "
+            echo " to disable compilation on the appropriate     "
+            echo " RustlerPrecompiled module in your             "
+            echo " application config.                           "
+            echo
+            echo " We think you need this:                       "
+            echo
+            echo -n " "
+            grep -Rl 'use RustlerPrecompiled' lib \
+              | xargs grep 'defmodule' \
+              | sed 's/defmodule \(.*\) do/config :${old.packageName}, \1, skip_compilation?: true/'
+            echo "***********************************************"
+            exit 1
+          }
+          trap suggestion ERR
+          ${old.buildPhase}
+        '';
       };
   };
 

lib/deps_nix.ex

@@ -246,6 +246,31 @@ defmodule DepsNix do
                   ln -s "$lib" "priv/native/$(basename "$lib")"
                 done
               '';
+
+              buildPhase = ''
+                suggestion() {
+                  echo "***********************************************"
+                  echo "                 deps_nix                      "
+                  echo
+                  echo " Rust dependency build failed.                 "
+                  echo
+                  echo " If you saw network errors, you might need     "
+                  echo " to disable compilation on the appropriate     "
+                  echo " RustlerPrecompiled module in your             "
+                  echo " application config.                           "
+                  echo
+                  echo " We think you need this:                       "
+                  echo
+                  echo -n " "
+                  grep -Rl 'use RustlerPrecompiled' lib \\
+                    | xargs grep 'defmodule' \\
+                    | sed 's/defmodule \\(.*\\) do/config :${old.packageName}, \\1, skip_compilation?: true/'
+                  echo "***********************************************"
+                  exit 1
+                }
+                trap suggestion ERR
+                ${old.buildPhase}
+              '';
             };
         };