Don't fallback to tempdir when required directories exist.

lib/bundler.rb

@@ -159,12 +159,13 @@ def ruby_scope
     def user_home
       @user_home ||= begin
         home = Bundler.rubygems.user_home
+        bundle_home = home ? File.join(home, ".bundle") : nil
 
         warning = if home.nil?
           "Your home directory is not set."
         elsif !File.directory?(home)
           "`#{home}` is not a directory."
-        elsif !File.writable?(home)
+        elsif !File.writable?(home) && (!File.directory?(bundle_home) || !File.writable?(bundle_home))
           "`#{home}` is not writable."
         end
 

spec/bundler/bundler_spec.rb

@@ -199,6 +199,57 @@
         allow(File).to receive(:writable?).with(path).and_return true
         expect(Bundler.user_home).to eq(Pathname(path))
       end
+
+      context "is not a directory" do
+        it "should issue a warning and return a temporary user home" do
+          path = "/home/oggy"
+          allow(Bundler.rubygems).to receive(:user_home).and_return(path)
+          allow(File).to receive(:directory?).with(path).and_return false
+          allow(Etc).to receive(:getlogin).and_return("USER")
+          allow(Dir).to receive(:tmpdir).and_return("/TMP")
+          allow(FileTest).to receive(:exist?).with("/TMP/bundler/home").and_return(true)
+          expect(FileUtils).to receive(:mkpath).with("/TMP/bundler/home/USER")
+          message = <<EOF
+`/home/oggy` is not a directory.
+Bundler will use `/TMP/bundler/home/USER' as your home directory temporarily.
+EOF
+          expect(Bundler.ui).to receive(:warn).with(message)
+          expect(Bundler.user_home).to eq(Pathname("/TMP/bundler/home/USER"))
+        end
+      end
+
+      context "is not writable" do
+        let(:path) { "/home/oggy" }
+        let(:dotbundle) { "/home/oggy/.bundle" }
+
+        it "should issue a warning and return a temporary user home" do
+          allow(Bundler.rubygems).to receive(:user_home).and_return(path)
+          allow(File).to receive(:directory?).with(path).and_return true
+          allow(File).to receive(:writable?).with(path).and_return false
+          allow(File).to receive(:directory?).with(dotbundle).and_return false
+          allow(Etc).to receive(:getlogin).and_return("USER")
+          allow(Dir).to receive(:tmpdir).and_return("/TMP")
+          allow(FileTest).to receive(:exist?).with("/TMP/bundler/home").and_return(true)
+          expect(FileUtils).to receive(:mkpath).with("/TMP/bundler/home/USER")
+          message = <<EOF
+`/home/oggy` is not writable.
+Bundler will use `/TMP/bundler/home/USER' as your home directory temporarily.
+EOF
+          expect(Bundler.ui).to receive(:warn).with(message)
+          expect(Bundler.user_home).to eq(Pathname("/TMP/bundler/home/USER"))
+        end
+
+        context ".bundle exists and have correct permissions" do
+          it "should return the user home" do
+            allow(Bundler.rubygems).to receive(:user_home).and_return(path)
+            allow(File).to receive(:directory?).with(path).and_return true
+            allow(File).to receive(:writable?).with(path).and_return false
+            allow(File).to receive(:directory?).with(dotbundle).and_return true
+            allow(File).to receive(:writable?).with(dotbundle).and_return true
+            expect(Bundler.user_home).to eq(Pathname(path))
+          end
+        end
+      end
     end
 
     context "home directory is not set" do