Treat empty credentials environment variables as unset. (#205)

.rubocop.yml

@@ -8,4 +8,4 @@ AllCops:
 Metrics/ClassLength:
   Max: 110
 Metrics/ModuleLength:
-  Max: 105
+  Max: 110

lib/googleauth/credentials_loader.rb

@@ -95,7 +95,7 @@ module Google
       #     * `:connection_builder` A `Proc` that returns a connection.
       def from_env scope = nil, options = {}
         options = interpret_options scope, options
-        if ENV.key? ENV_VAR
+        if ENV.key?(ENV_VAR) && !ENV[ENV_VAR].empty?
           path = ENV[ENV_VAR]
           raise "file #{path} does not exist" unless File.exist? path
           File.open path do |f|
@@ -192,11 +192,13 @@ module Google
       end
 
       def service_account_env_vars?
-        ([PRIVATE_KEY_VAR, CLIENT_EMAIL_VAR] - ENV.keys).empty?
+        ([PRIVATE_KEY_VAR, CLIENT_EMAIL_VAR] - ENV.keys).empty? &&
+          !ENV.to_h.fetch_values(PRIVATE_KEY_VAR, CLIENT_EMAIL_VAR).join(" ").empty?
       end
 
       def authorized_user_env_vars?
-        ([CLIENT_ID_VAR, CLIENT_SECRET_VAR, REFRESH_TOKEN_VAR] - ENV.keys).empty?
+        ([CLIENT_ID_VAR, CLIENT_SECRET_VAR, REFRESH_TOKEN_VAR] - ENV.keys).empty? &&
+          !ENV.to_h.fetch_values(CLIENT_ID_VAR, CLIENT_SECRET_VAR, REFRESH_TOKEN_VAR).join(" ").empty?
       end
     end
   end

spec/googleauth/service_account_spec.rb

@@ -187,6 +187,11 @@ describe Google::Auth::ServiceAccountCredentials do
       expect(ServiceAccountCredentials.from_env(@scope)).to be_nil
     end
 
+    it "returns nil if the GOOGLE_APPLICATION_CREDENTIALS is empty" do
+      ENV[@var_name] = ""
+      expect(ServiceAccountCredentials.from_env(@scope)).to be_nil
+    end
+
     it "fails if the GOOGLE_APPLICATION_CREDENTIALS path does not exist" do
       ENV.delete @var_name unless ENV[@var_name].nil?
       expect(ServiceAccountCredentials.from_env(@scope)).to be_nil
@@ -390,6 +395,11 @@ describe Google::Auth::ServiceAccountJwtHeaderCredentials do
       expect(clz.from_env).to be_nil
     end
 
+    it "returns nil if the GOOGLE_APPLICATION_CREDENTIALS is empty" do
+      ENV[@var_name] = ""
+      expect(clz.from_env).to be_nil
+    end
+
     it "fails if the GOOGLE_APPLICATION_CREDENTIALS path does not exist" do
       ENV.delete @var_name unless ENV[@var_name].nil?
       expect(clz.from_env).to be_nil

spec/googleauth/user_refresh_spec.rb

@@ -106,6 +106,11 @@ describe Google::Auth::UserRefreshCredentials do
       expect(UserRefreshCredentials.from_env(@scope)).to be_nil
     end
 
+    it "returns nil if the GOOGLE_APPLICATION_CREDENTIALS is empty" do
+      ENV[@var_name] = ""
+      expect(UserRefreshCredentials.from_env(@scope)).to be_nil
+    end
+
     it "fails if the GOOGLE_APPLICATION_CREDENTIALS path does not exist" do
       ENV.delete @var_name unless ENV[@var_name].nil?
       expect(UserRefreshCredentials.from_env(@scope)).to be_nil