Allow CSV.open with StringIO argument

[MarcPer]

Fix #300

[kou]

Could you rebase on main? Our CI on master broken... and I've fixed it now.

[MarcPer]

Could you rebase on main? Our CI on master broken... and I've fixed it now.

Thank you, I've rebase it now.

[kou]

Thanks. But sorry... The master CI was broken... I've fixed it. Could you rebase on master again?

[MarcPer]

Thanks. But sorry... The master CI was broken... I've fixed it. Could you rebase on master again?

No problem, I rebased it now.

[MarcPer]

I'm assuming the test failures are related to https://bugs.ruby-lang.org/issues/20526, right?

[kou]

Hmm. It should be fixed by https://github.com/ruby/csv/commit/47bf76fe7fb3f990802519a2f3af96fbcdc432b5 . Could you rebase again?

[MarcPer]

Rebased it, and removed a now unneeded check when closing the IO within CSV#open.

[kou]

Ah, the failed test is an added test.

Does this work?

diff --git a/lib/csv.rb b/lib/csv.rb
index 7511ced..d2d1c57 100644
--- a/lib/csv.rb
+++ b/lib/csv.rb
@@ -1591,7 +1591,10 @@ class CSV
       # wrap a File opened with the remaining +args+ with no newline
       # decorator
       file_opts = {}
-      may_enable_bom_deletection_automatically(mode, options, file_opts)
+      may_enable_bom_deletection_automatically(filename_or_io,
+                                               mode,
+                                               options,
+                                               file_opts)
       file_opts.merge!(options)
       unless file_opts.key?(:newline)
         file_opts[:universal_newline] ||= false
@@ -1900,10 +1903,15 @@ class CSV
     private_constant :ON_WINDOWS
 
     private
-    def may_enable_bom_deletection_automatically(mode, options, file_opts)
-      # "bom|utf-8" may be buggy on Windows:
-      # https://bugs.ruby-lang.org/issues/20526
-      return if ON_WINDOWS
+    def may_enable_bom_deletection_automatically(filename_or_io,
+                                                 mode,
+                                                 options,
+                                                 file_opts)
+      unless filename_or_io.is_a?(StringIO)
+        # "bom|utf-8" may be buggy on Windows:
+        # https://bugs.ruby-lang.org/issues/20526
+        return if ON_WINDOWS
+      end
       return unless Encoding.default_external == Encoding::UTF_8
       return if options.key?(:encoding)
       return if options.key?(:external_encoding)

[MarcPer]

Sorry, I was away for a while. I saw that support to StringIO was dropped for Ruby 2.6 and earlier, before handling of BOM encoding was added. Given that, would it be okay to skip the new tests for StringIO if RUBY_VERSION < "2.7"? Otherwise, the CSV gem might have to deal itself with detection and stripping of BOM.

[kou]

Thanks.