[Validator] Updates validation for dot_swift_version file to prevent failure…

[Validator] Updates validation for dot_swift_version file to prevent failure message for non-swift pods.

Responding to PR comments

Fixes incorrect test_swiftpod method call in validator_spec

CHANGELOG.md

@@ -16,6 +16,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
   [#1698](https://github.com/CocoaPods/CocoaPods/issues/1698) 
 
+* Prevents need for .swift-version file in Objective-C pods  
+  [Austin Emmons](https://github.com/atreat)
+  [#6742](https://github.com/CocoaPods/CocoaPods/issues/6742) 
+
 ##### Bug Fixes
 
 * Fix pod install error from 1.2.1 when working with static lib-only projects.  

lib/cocoapods/validator.rb

@@ -146,15 +146,8 @@ module Pod
         reasons << 'all results apply only to public specs, but you can use ' \
                    '`--private` to ignore them if linting the specification for a private pod'
       end
-      if dot_swift_version.nil?
-        reasons.to_sentence + ".\n[!] The validator for Swift projects uses " \
-          'Swift 3.0 by default, if you are using a different version of ' \
-          'swift you can use a `.swift-version` file to set the version for ' \
-          "your Pod. For example to use Swift 2.3, run: \n" \
-          '    `echo "2.3" > .swift-version`'
-      else
-        reasons.to_sentence
-      end
+
+      reasons.to_sentence
     end
 
     #-------------------------------------------------------------------------#
@@ -308,6 +301,7 @@ module Pod
           download_pod
           check_file_patterns
           install_pod
+          validate_dot_swift_version
           add_app_project_import
           validate_vendored_dynamic_frameworks
           build_pod
@@ -382,6 +376,17 @@ module Pod
       validate_url(spec.documentation_url) if spec.documentation_url
     end
 
+    def validate_dot_swift_version
+      if !used_swift_version.nil? && dot_swift_version.nil?
+        warning(:swift_version,
+                'The validator for Swift projects uses ' \
+                'Swift 3.0 by default, if you are using a different version of ' \
+                'swift you can use a `.swift-version` file to set the version for ' \
+                "your Pod. For example to use Swift 2.3, run: \n" \
+                '    `echo "2.3" > .swift-version`')
+      end
+    end
+
     def setup_validation_environment
       validation_dir.rmtree if validation_dir.exist?
       validation_dir.mkpath

spec/unit/validator_spec.rb

@@ -870,8 +870,14 @@ module Pod
         validator
       end
 
-      it 'fails on deployment target < iOS 8 for Swift Pods' do
+      def test_swiftpod_with_dot_swift_version(version = '3.1.0')
         validator = test_swiftpod
+        validator.stubs(:dot_swift_version).returns(version)
+        validator
+      end
+
+      it 'fails on deployment target < iOS 8 for Swift Pods' do
+        validator = test_swiftpod_with_dot_swift_version
         validator.validate
 
         validator.results.map(&:to_s).first.should.match /dynamic frameworks.*iOS > 8/
@@ -881,7 +887,7 @@ module Pod
       it 'succeeds on deployment target < iOS 8 for Swift Pods using XCTest' do
         Specification::Consumer.any_instance.stubs(:frameworks).returns(%w(XCTest))
 
-        validator = test_swiftpod
+        validator = test_swiftpod_with_dot_swift_version
         validator.validate
         validator.results.count.should == 0
       end
@@ -889,27 +895,36 @@ module Pod
       it 'succeeds on deployment targets >= iOS 8 for Swift Pods' do
         Specification.any_instance.stubs(:deployment_target).returns('9.0')
 
-        validator = test_swiftpod
+        validator = test_swiftpod_with_dot_swift_version
         validator.validate
 
         validator.results.count.should == 0
       end
 
-      it 'tells users about the .swift-version file if the validation fails' do
+      it 'fails without the presence of a .swift-version file for Swift Pods' do
         Specification.any_instance.stubs(:deployment_target).returns('9.0')
 
         validator = test_swiftpod
-        validator.stubs(:validated?).returns(false)
-        result = Validator::Result.new(:error, 'attribute', 'message')
-        validator.stubs(:results).returns([result])
+        validator.validate
+        validator.results.count.should == 1
 
-        validator.failure_reason.should == "1 error.\n[!] The validator for " \
+        result = validator.results.first
+        result.type.should == :warning
+        result.message.should == 'The validator for ' \
           'Swift projects uses Swift 3.0 by default, if you are using a ' \
           'different version of swift you can use a `.swift-version` file ' \
           'to set the version for your Pod. For example to use Swift 2.3, ' \
           "run: \n    `echo \"2.3\" > .swift-version`"
       end
 
+      it 'succeeds with the presence of a .swift-version file for Swift Pods' do
+        Specification.any_instance.stubs(:deployment_target).returns('9.0')
+
+        validator = test_swiftpod_with_dot_swift_version
+        validator.validate
+        validator.results.count.should == 0
+      end
+
       describe '#swift_version' do
         it 'defaults to Swift 3.0' do
           validator = test_swiftpod