From 4843149b6ac82754e7a4e1c983f2a90b8f735d8d Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Tue, 5 Mar 2019 20:46:23 +1100
Subject: [PATCH] Make error description available as "%val{error}" during
 catch blocks

Fixes #2761
---
 doc/pages/commands.asciidoc       |  4 +++-
 src/commands.cc                   | 17 +++++++++++++----
 test/compose/catch-error-desc/cmd |  1 +
 test/compose/catch-error-desc/in  |  1 +
 test/compose/catch-error-desc/out |  1 +
 test/compose/catch-error-desc/rc  |  1 +
 6 files changed, 20 insertions(+), 5 deletions(-)
 create mode 100644 test/compose/catch-error-desc/cmd
 create mode 100644 test/compose/catch-error-desc/in
 create mode 100644 test/compose/catch-error-desc/out
 create mode 100644 test/compose/catch-error-desc/rc

diff --git a/doc/pages/commands.asciidoc b/doc/pages/commands.asciidoc
index f24be1a9..db7d1834 100644
--- a/doc/pages/commands.asciidoc
+++ b/doc/pages/commands.asciidoc
@@ -278,7 +278,9 @@ but not really useful in that context.
     done on error, the catch part can be omitted. If an error is raised
     in the *on_error_commands*, that error is propagated, except if
     another *catch* and *on_error_commands* parameter follows, in which
-    case those commands get executed, and so-on.
+    case those commands get executed, and so-on. During error commands,
+    the description of the last raiser error is available as `$kak_error`
+    in the shell, or `%val{error}` in commands.
 
 *nop*::
     does nothing, but arguments will be evaluated (e.g. shell expansion)
diff --git a/src/commands.cc b/src/commands.cc
index 5f7e1530..0e099b09 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -2080,17 +2080,26 @@ const CommandDesc try_catch_cmd = {
         }
 
         CommandManager& command_manager = CommandManager::instance();
+        Optional<ShellContext> shell_context_with_error;
         for (size_t i = 0; i < parser.positional_count(); i += 2)
         {
             if (i == 0 or i < parser.positional_count() - 1)
             {
-                try {
-                    command_manager.execute(parser[i], context, shell_context);
+                try
+                {
+                    command_manager.execute(parser[i], context,
+                                            shell_context_with_error.value_or(shell_context));
                     return;
-                } catch (runtime_error&) {}
+                }
+                catch (const runtime_error& error)
+                {
+                    shell_context_with_error.emplace(shell_context);
+                    shell_context_with_error->env_vars[StringView{"error"}] = error.what().str();
+                }
             }
             else
-                command_manager.execute(parser[i], context, shell_context);
+                command_manager.execute(parser[i], context,
+                                        shell_context_with_error.value_or(shell_context));
         }
     }
 };
diff --git a/test/compose/catch-error-desc/cmd b/test/compose/catch-error-desc/cmd
new file mode 100644
index 00000000..d41464ed
--- /dev/null
+++ b/test/compose/catch-error-desc/cmd
@@ -0,0 +1 @@
+:error<ret>
diff --git a/test/compose/catch-error-desc/in b/test/compose/catch-error-desc/in
new file mode 100644
index 00000000..8b137891
--- /dev/null
+++ b/test/compose/catch-error-desc/in
@@ -0,0 +1 @@
+
diff --git a/test/compose/catch-error-desc/out b/test/compose/catch-error-desc/out
new file mode 100644
index 00000000..43fd3e4b
--- /dev/null
+++ b/test/compose/catch-error-desc/out
@@ -0,0 +1 @@
+no such command: 'non-existing-command'
diff --git a/test/compose/catch-error-desc/rc b/test/compose/catch-error-desc/rc
new file mode 100644
index 00000000..82bde5dd
--- /dev/null
+++ b/test/compose/catch-error-desc/rc
@@ -0,0 +1 @@
+define-command error %{ try %{ non-existing-command } catch %{ exec i "%val{error}" <esc> } }