Improve messaging when dependencies conflict

CHANGELOG.md

@@ -12,6 +12,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Samuel Giddins](https://github.com/segiddins)
   [#5218](https://github.com/CocoaPods/CocoaPods/issues/5218)
 
+* Improvements to the error messaging around missing dependencies.  
+  [Orta Therox](https://github.com/orta)
+  [#5260](https://github.com/CocoaPods/CocoaPods/issues/5260)
+
 ##### Bug Fixes
 
 * None.  

lib/cocoapods/resolver.rb

@@ -419,20 +419,22 @@ module Pod
             end
             message << "\nYou should explicitly specify the version in order to install a pre-release version"
           elsif !conflict.existing
-            conflict.requirements.values.flatten.uniq.each do |r|
-              if search_for(r).empty?
-                # There are no existing specification inside any of the spec repos with given requirements.
-                message << "\n\nNone of your spec sources contain a spec satisfying the dependency: `#{r}`." \
-                  "\n\nYou have either:" \
-                  "\n * out-of-date source repos which you can update with `pod repo update`." \
-                  "\n * mistyped the name or version." \
-                  "\n * not added the source repo that hosts the Podspec to your Podfile." \
-                  "\n\nNote: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default."
-
-              else
-                message << "\n\nSpecs satisfying the `#{r}` dependency were found, " \
-                  'but they required a higher minimum deployment target.'
-              end
+            conflicts = conflict.requirements.values.flatten.uniq
+            found_conflicted_specs = conflicts.reject { |c| search_for(c).empty? }
+            if found_conflicted_specs.empty?
+              # There are no existing specification inside any of the spec repos with given requirements.
+              dependencies = conflicts.count == 1 ? 'dependency' : 'dependencies'
+              message << "\n\nNone of your spec sources contain a spec satisfying "\
+                "the #{dependencies}: `#{conflicts.join(', ')}`." \
+                "\n\nYou have either:" \
+                "\n * out-of-date source repos which you can update with `pod repo update`." \
+                "\n * mistyped the name or version." \
+                "\n * not added the source repo that hosts the Podspec to your Podfile." \
+                "\n\nNote: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default."
+
+            else
+              message << "\n\nSpecs satisfying the `#{conflicts.join(', ')}` dependency were found, " \
+                'but they required a higher minimum deployment target.'
             end
           end
         end

spec/unit/resolver_spec.rb

@@ -369,6 +369,27 @@ module Pod
         e.message.should.match(/Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default./)
       end
 
+      it 'raises with a list of dependencies if there are many dependencies but no versions of a dependency exists' do
+        podfile = Podfile.new do
+          platform :ios
+          pod 'AFNetworking', '3.0.1'
+        end
+        locked_deps = dependency_graph_from_array([Dependency.new('AFNetworking', '= 1.4')])
+
+        resolver = Resolver.new(config.sandbox, podfile, locked_deps, config.sources_manager.all)
+        e = lambda { resolver.resolve }.should.raise Informative
+        e.message.should.match(/Unable to satisfy the following requirements/)
+        e.message.should.match(/`AFNetworking \(= 3.0.1\)` required by `Podfile`/)
+        e.message.should.match(/`AFNetworking \(= 1.4\)` required by `Podfile.lock`/)
+        e.message.should.match(/None of your spec sources contain a spec satisfying the dependencies:/)
+        e.message.should.match(/`AFNetworking \(= 3.0.1\), AFNetworking \(= 1.4\)`/)
+        e.message.should.match(/You have either:/)
+        e.message.should.match(/ * out-of-date source repos which you can update with `pod repo update`/)
+        e.message.should.match(/ * not added the source repo that hosts the Podspec to your Podfile./)
+        e.message.should.match(/ * out-of-date source repos which you can update with `pod repo update`/)
+        e.message.should.match(/Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default./)
+      end
+
       it 'takes into account locked dependencies' do
         podfile = Podfile.new do
           platform :ios