「〜たはいいが、……」grammar pattern


I'm playing a video game called 善人シボウデス, and I noticed some grammar I'm not
familiar with:

> ところでこのラジオ、電源ケーブルに **つないだはいいが** 、この後どうすればいいんだろう？

This was said by the main character, who generally speaks in Standard
Japanese. But I didn't know you could say 〜た＋は like this in Standard Japanese,
so I tried looking it up. I mostly looked under た and は, but I couldn't find a
dictionary that covered it.

Later, in another part of the game, I noticed the same character saying a very
similar sentence:

> 電源を **入れたはいいが** 、こいつでなにをスキャンすればいいんだ？

So I started to wonder if this 〜たは was part of a larger pattern. For example,
is this 〜たは always followed by 良い and some kind of contrastive conjunctive
particle like が・けど・ものの? I searched online and saw similar examples:

> 【子役事務所】に **入れたはいいけど** 。。。どうしたらいいの？

Can anyone explain this pattern?




The `verb-た` + `は` + `いい/よかった` + `contradictory conj.` makes a set phrase
roughly means "have/had successfully V-ed, but now/then (the problem
is/was)...". It's one of a few idioms still allowed with direct nominalization
(technically, 連体形準体法). You can rephrase it in regular modern grammar as
`～たまではいいが` or `～たのはいいが` with meaning (almost) unchanged. While those modern
patterns also accept present form of the verb (`～するまではいいが`), the idiomatic one
never allow *`～するはいいが`.

`verb` + `は` combination generally doesn't show much productivity today, far
less than `verb` + `に`. Most surviving examples are old sayings or proverbs
based on Edo-or-earlier-period colloquial language (e.g.
[聞くは一時の恥、聞かぬは一生の恥](http://kotowaza-allguide.com/ki/kikanuwaissyounohaji.html);
I couldn't find `～たは` examples).

* * *

(Maybe) related papers:
「[滑稽本と人情本における連体形準体法，準体助詞について](https://m-repo.lib.meiji.ac.jp/dspace/bitstream/10291/16085/1/bungakuronshu_36_43.pdf)」,
「[準体助詞の全国分布とその成立経緯](https://m-repo.lib.meiji.ac.jp/dspace/bitstream/10291/16085/1/bungakuronshu_36_43.pdf)」




The `verb-た` + `は` + `いい/よかった` + `contradictory conj.` makes a set phrase
roughly means "have/had successfully V-ed, but now/then (the problem
is/was)...". It's one of a few idioms still allowed with direct nominalization
(technically, 連体形準体法). You can rephrase it in regular modern grammar as
`～たまではいいが` or `～たのはいいが` with meaning (almost) unchanged. While those modern
patterns also accept present form of the verb (`～するまではいいが`), the idiomatic one
never allow *`～するはいいが`.

`verb` + `は` combination generally doesn't show much productivity today, far
less than `verb` + `に`. Most surviving examples are old sayings or proverbs
based on Edo-or-earlier-period colloquial language (e.g.
[聞くは一時の恥、聞かぬは一生の恥](http://kotowaza-allguide.com/ki/kikanuwaissyounohaji.html);
I couldn't find `～たは` examples).

* * *

(Maybe) related papers:
「[滑稽本と人情本における連体形準体法，準体助詞について](https://m-repo.lib.meiji.ac.jp/dspace/bitstream/10291/16085/1/bungakuronshu_36_43.pdf)」,
「[準体助詞の全国分布とその成立経緯](https://m-repo.lib.meiji.ac.jp/dspace/bitstream/10291/16085/1/bungakuronshu_36_43.pdf)」

