Improve error reporting around bad sources

lib/rubygems/command_manager.rb

@@ -122,6 +122,17 @@ def run(args)
     alert_error "While executing gem ... (#{ex.class})\n    #{ex.to_s}"
     ui.errs.puts "\t#{ex.backtrace.join "\n\t"}" if
       Gem.configuration.backtrace
+
+    if Gem.configuration.really_verbose and \
+         ex.kind_of?(Gem::Exception) and ex.source_exception
+      e = ex.source_exception
+
+      ui.errs.puts "Because of: (#{e.class})\n    #{e.to_s}"
+      if Gem.configuration.backtrace
+        ui.errs.puts "\t#{e.backtrace.join "\n\t"}"
+      end
+    end
+
     terminate_interaction(1)
   rescue Interrupt
     alert_error "Interrupted"

lib/rubygems/commands/sources_command.rb

@@ -77,7 +77,7 @@ def execute
       rescue URI::Error, ArgumentError
         say "#{source_uri} is not a URI"
         terminate_interaction 1
-      rescue Gem::RemoteFetcher::FetchError => e
+      rescue Gem::RemoteFetcher::FetchError, Gem::SourceError => e
         say "Error fetching #{source_uri}:\n\t#{e.message}"
         terminate_interaction 1
       end

lib/rubygems/exceptions.rb

@@ -1,7 +1,9 @@
 ##
 # Base exception class for RubyGems.  All exception raised by RubyGems are a
 # subclass of this one.
-class Gem::Exception < RuntimeError; end
+class Gem::Exception < RuntimeError
+  attr_accessor :source_exception
+end
 
 class Gem::CommandLineError < Gem::Exception; end
 
@@ -89,3 +91,21 @@ def initialize(exit_code)
   end
 
 end
+
+##
+# An error that indicates there is an error with the source
+# itself (such as the latest_spec file being invalid)
+
+class Gem::SourceError < Gem::Exception
+  def initialize(message, uri)
+    @uri = uri
+    super message
+  end
+
+  attr_reader :uri
+
+  def to_s
+    "#{super} (#{@uri})"
+  end
+end
+

lib/rubygems/remote_fetcher.rb

@@ -32,6 +32,13 @@ def to_s # :nodoc:
 
   end
 
+  ##
+  # A FetchError that indicates that the reason for not being
+  # able to fetch data was that the host could not be contacted
+
+  class UnknownHostError < FetchError
+  end
+
   @fetcher = nil
 
   ##
@@ -221,18 +228,32 @@ def fetch_path(uri, mtime = nil, head = false)
     uri = URI.parse uri unless URI::Generic === uri
 
     raise ArgumentError, "bad uri: #{uri}" unless uri
-    raise ArgumentError, "uri scheme is invalid: #{uri.scheme.inspect}" unless
-      uri.scheme
+
+    unless uri.scheme
+      raise ArgumentError, "uri scheme is invalid: #{uri.scheme.inspect}"
+    end
 
     data = send "fetch_#{uri.scheme}", uri, mtime, head
-    data = Gem.gunzip data if data and not head and uri.to_s =~ /gz$/
+
+    if data and !head and uri.to_s =~ /gz$/
+      begin
+        data = Gem.gunzip data
+      rescue Zlib::GzipFile::Error
+        raise FetchError.new("server did not return a valid file", uri.to_s)
+      end
+    end
+
     data
   rescue FetchError
     raise
   rescue Timeout::Error
-    raise FetchError.new('timed out', uri.to_s)
+    raise UnknownHostError.new('timed out', uri.to_s)
   rescue IOError, SocketError, SystemCallError => e
-    raise FetchError.new("#{e.class}: #{e}", uri.to_s)
+    if e.message =~ /getaddrinfo/
+      raise UnknownHostError.new('no such name', uri.to_s)
+    else
+      raise FetchError.new("#{e.class}: #{e}", uri.to_s)
+    end
   end
 
   ##
@@ -246,9 +267,13 @@ def cache_update_path(uri, path = nil)
       Gem.read_binary(path)
     else
       data = fetch_path(uri)
-      open(path, 'wb') do |io|
-        io.write data
-      end if path
+
+      if path
+        open(path, 'wb') do |io|
+          io.write data
+        end
+      end
+
       data
     end
   end

lib/rubygems/spec_fetcher.rb

@@ -256,11 +256,21 @@ def load_specs(source_uri, file)
     local_file = File.join(cache_dir, file_name)
     retried    = false
 
-    spec_dump = if @update_cache then
-      FileUtils.mkdir_p cache_dir
-      @fetcher.cache_update_path(spec_path, local_file)
-    else
-      @fetcher.cache_update_path(spec_path)
+    begin
+      spec_dump = if @update_cache then
+                    FileUtils.mkdir_p cache_dir
+                    @fetcher.cache_update_path(spec_path, local_file)
+                  else
+                    @fetcher.cache_update_path(spec_path)
+                  end
+    rescue Gem::RemoteFetcher::UnknownHostError => e
+      exc = Gem::SourceError.new("Could not contact source", source_uri)
+      exc.source_exception = e
+      raise exc
+    rescue Gem::RemoteFetcher::FetchError => e
+      exc = Gem::SourceError.new("Bad source, unable to get specs", source_uri)
+      exc.source_exception = e
+      raise exc
     end
 
     begin

test/rubygems/test_gem_commands_sources_command.rb

@@ -90,7 +90,7 @@ def test_execute_add_nonexistent_source
 
     expected = <<-EOF
 Error fetching http://beta-gems.example.com:
-\tit died (#{uri})
+\tBad source, unable to get specs (http://beta-gems.example.com)
     EOF
 
     assert_equal expected, @ui.output