(#7269) Better error reporting for bad render formats.

Previously we would try and send `nil` to a class to render an unsupported
format, which was bad.  Worse, we would only discover this *after* the fact,
when we tried to render, so the entire action had run and the result was lost
to the world.

Instead, validate the parameter early and fail during option parsing.  This
has less nice error reporting than we can get handling it later[1], but it
gets us a much better overall set of behaviour.

[1] puppet/application.rb will print and exit, rather than raising, when the
    option handler fails; this will improve when we unify face and application
    options properly.

Reviewed-By: Max Martin <max@puppetlabs.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/lib/puppet/application/face_base.rb b/lib/puppet/application/face_base.rb
index cc62257c7..d28a8af3b 100644
--- a/lib/puppet/application/face_base.rb
+++ b/lib/puppet/application/face_base.rb
@@ -15,8 +15,14 @@ class Puppet::Application::FaceBase < Puppet::Application
     Puppet::Util::Log.level = :info
   end
 
-  option("--render-as FORMAT") do |arg|
-    @render_as = arg.to_sym
+  option("--render-as FORMAT") do |_arg|
+    format = _arg.to_sym
+    unless @render_method = Puppet::Network::FormatHandler.format(format)
+      unless format == :for_humans or format == :json
+        raise ArgumentError, "I don't know how to render '#{format}'"
+      end
+    end
+    @render_as = format
   end
 
   option("--mode RUNMODE", "-r") do |arg|
@@ -36,18 +42,12 @@ class Puppet::Application::FaceBase < Puppet::Application
       result = hook.call(result)
     end
 
-    begin
-      render_method = Puppet::Network::FormatHandler.format(format).render_method
-    rescue
-      render_method = nil
-    end
-
     if format == :for_humans then
       render_for_humans(result)
-    elsif format == :json or render_method == "to_pson"
+    elsif format == :json or @render_method == "to_pson"
       PSON::pretty_generate(result, :allow_nan => true, :max_nesting => false)
     else
-      result.send(render_method)
+      result.send(@render_method)
     end
   end