Do not crash when attempting to install pod with no supported targets

CHANGELOG.md

@@ -14,6 +14,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
 
 ##### Bug Fixes
 
+* Do not crash when attempting to install pod with no supported targets.  
+  [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
+  [#6465](https://github.com/CocoaPods/CocoaPods/issues/6465)
+
 * Correctly handle `OTHER_LDFLAGS` for targets with inherit search paths and source pods.  
   [Justin Martin](https://github.com/justinseanmartin)
   [Dimitris Koutsogiorgas](https://github.com/dnkoutso)

lib/cocoapods/installer.rb

@@ -338,6 +338,8 @@ module Pod
         end
       end
 
+      raise Informative, "Could not install '#{pod_name}' pod. There is no target that supports it." if specs_by_platform.empty?
+
       @pod_installers ||= []
       pod_installer = PodSourceInstaller.new(sandbox, specs_by_platform, :can_cache => installation_options.clean?)
       @pod_installers << pod_installer

lib/cocoapods/installer/analyzer/target_inspector.rb

@@ -4,6 +4,8 @@ module Pod
   class Installer
     class Analyzer
       class TargetInspector
+        PLATFORM_INFO_URL = 'https://guides.cocoapods.org/syntax/podfile.html#platform'.freeze
+
         # @return [TargetDefinition] the target definition to inspect
         #
         attr_accessor :target_definition
@@ -159,6 +161,10 @@ module Pod
                   "Unable to determine the platform for the `#{target_definition.name}` target."
           end
 
+          UI.warn "Automatically assigning platform #{name} with version #{deployment_target} " \
+            "on target #{target_definition.name} because no platform was specified. " \
+            "Please specify a platform for this target in your Podfile. See `#{PLATFORM_INFO_URL}`."
+
           target_definition.set_platform(name, deployment_target)
           Platform.new(name, deployment_target)
         end

cocoapods-integration-specs @ 29e64c27

-Subproject commit e62f3157268e9d2fe634dfab2560c89013d89240
+Subproject commit 29e64c27eff470779877e8ffc24fdaf707f261a8

spec/unit/installer/analyzer/target_inspector_spec.rb

@@ -232,6 +232,9 @@ module Pod
         target_inspector = TargetInspector.new(target_definition, config.installation_root)
         platforms = target_inspector.send(:compute_platform, user_targets)
         platforms.should == Platform.new(:ios, '4.0')
+        UI.warnings.should.include 'Automatically assigning platform ios with version 4.0 on target default because no ' \
+          'platform was specified. Please specify a platform for this target in your Podfile. ' \
+          'See `https://guides.cocoapods.org/syntax/podfile.html#platform`.'
       end
 
       it 'uses the lowest deployment target of the user targets if inferring the platform' do

spec/unit/installer_spec.rb

@@ -540,6 +540,16 @@ module Pod
           UI.output.should.include 'was 1.0'
         end
 
+        it 'raises when it attempts to install pod source with no target supporting it' do
+          spec = fixture_spec('banana-lib/BananaLib.podspec')
+          pod_target = PodTarget.new([spec], [fixture_target_definition], config.sandbox)
+          pod_target.stubs(:platform).returns(:ios)
+          @installer.stubs(:pod_targets).returns([pod_target])
+          should.raise Informative do
+            @installer.send(:create_pod_installer, 'RandomPod')
+          end.message.should.include 'Could not install \'RandomPod\' pod. There is no target that supports it.'
+        end
+
         #--------------------------------------#
 
         describe '#clean' do