[ruby/irb] Return only commands when completing help command's

argument
(https://github.com/ruby/irb/pull/973)

The command only takes command names as arguments, so we should only
return command names as candidates.

This will help users find a command faster as completion will be
another useful hint too.

https://github.com/ruby/irb/commit/7b6557cc24

1 files changed, 29 insertions, 9 deletions

diff --git a/lib/irb/completion.rb b/lib/irb/completion.rb
index a3d89373c3..7f102dcdf4 100644
--- a/lib/irb/completion.rb
+++ b/lib/irb/completion.rb
@@ -33,6 +33,8 @@ module IRB
       yield
     ]
 
+    HELP_COMMAND_PREPOSING = /\Ahelp\s+/
+
     def completion_candidates(preposing, target, postposing, bind:)
       raise NotImplementedError
     end
@@ -86,8 +88,8 @@ module IRB
         )
     end
 
-    def command_completions(preposing, target)
-      if preposing.empty? && !target.empty?
+    def command_candidates(target)
+      if !target.empty?
         IRB::Command.command_names.select { _1.start_with?(target) }
       else
         []
@@ -111,8 +113,18 @@ module IRB
     end
 
     def completion_candidates(preposing, target, _postposing, bind:)
-      commands = command_completions(preposing, target)
+      # When completing the argument of `help` command, only commands should be candidates
+      return command_candidates(target) if preposing.match?(HELP_COMMAND_PREPOSING)
+
+      commands = if preposing.empty?
+        command_candidates(target)
+      # It doesn't make sense to propose commands with other preposing
+      else
+        []
+      end
+
       result = ReplTypeCompletor.analyze(preposing + target, binding: bind, filename: @context.irb_path)
+
       return commands unless result
 
       commands | result.completion_candidates.map { target + _1 }
@@ -187,12 +199,20 @@ module IRB
     end
 
     def completion_candidates(preposing, target, postposing, bind:)
-      if preposing && postposing
-        result = complete_require_path(target, preposing, postposing)
-        return result if result
+      if result = complete_require_path(target, preposing, postposing)
+        return result
       end
-      commands = command_completions(preposing || '', target)
-      commands | retrieve_completion_data(target, bind: bind, doc_namespace: false).compact.map{ |i| i.encode(Encoding.default_external) }
+
+      commands = command_candidates(target)
+
+      # When completing the argument of `help` command, only commands should be candidates
+      return commands if preposing.match?(HELP_COMMAND_PREPOSING)
+
+      # It doesn't make sense to propose commands with other preposing
+      commands = [] unless preposing.empty?
+
+      completion_data = retrieve_completion_data(target, bind: bind, doc_namespace: false).compact.map{ |i| i.encode(Encoding.default_external) }
+      commands | completion_data
     end
 
     def doc_namespace(_preposing, matched, _postposing, bind:)
@@ -470,7 +490,7 @@ module IRB
       end
     end
     CompletionProc = ->(target, preposing = nil, postposing = nil) {
-      regexp_completor.completion_candidates(preposing, target, postposing, bind: IRB.conf[:MAIN_CONTEXT].workspace.binding)
+      regexp_completor.completion_candidates(preposing || '', target, postposing || '', bind: IRB.conf[:MAIN_CONTEXT].workspace.binding)
     }
   end
   deprecate_constant :InputCompletor