From 5327953d299eba0b6de4e88bacf4bba9022bb5e2 Mon Sep 17 00:00:00 2001
From: Rebecca Turner <rbt@sent.as>
Date: Thu, 12 Dec 2024 15:49:25 -0800
Subject: [PATCH] Log fetchers as they're run

It's very difficult to figure out which error messages are fatal or even
which fetchers they correspond to. To fix this, we print the command
we're going to run to attempt a fetch for each fetcher we try.

Before:

```
$ cabal2nix https://github.com/iand675/hs-sqlcommenter.git
error: failed to open archive: Unrecognized archive format
Initialized empty Git repository in /private/tmp/git-checkout-tmp-REpu3aRm/hs-sqlcommenter/.git/
remote: Enumerating objects: 16, done.
remote: Counting objects: 100% (16/16), done.
remote: Compressing objects: 100% (12/12), done.
remote: Total 16 (delta 0), reused 16 (delta 0), pack-reused 0 (from 0)
Unpacking objects: 100% (16/16), 14.14 KiB | 1.18 MiB/s, done.
From https://github.com/iand675/hs-sqlcommenter
 * branch            HEAD       -> FETCH_HEAD
Switched to a new branch 'fetchgit'
removing `.git'...
error: path '/tmp' is a symlink
abort: 'https://github.com/iand675/hs-sqlcommenter.git' does not appear to be an hg repository:
---%<--- (text/html; charset=utf-8)
...
```

After:

```
$ cabal2nix https://github.com/iand675/hs-sqlcommenter.git
$ nix-prefetch-url https://github.com/iand675/hs-sqlcommenter.git
$ nix-prefetch-url --unpack https://github.com/iand675/hs-sqlcommenter.git
error: failed to open archive: Unrecognized archive format
[0.1 MiB DL] $ nix-prefetch-git --fetch-submodules https://github.com/iand675/hs-sqlcommenter.git
Initialized empty Git repository in /private/tmp/git-checkout-tmp-DRzhuqlX/hs-sqlcommenter/.git/
remote: Enumerating objects: 16, done.
remote: Counting objects: 100% (16/16), done.
remote: Compressing objects: 100% (12/12), done.
remote: Total 16 (delta 0), reused 16 (delta 0), pack-reused 0 (from 0)
Unpacking objects: 100% (16/16), 14.14 KiB | 336.00 KiB/s, done.
From https://github.com/iand675/hs-sqlcommenter
 * branch            HEAD       -> FETCH_HEAD
Switched to a new branch 'fetchgit'
removing `.git'...
error: path '/tmp' is a symlink
$ nix-prefetch-hg https://github.com/iand675/hs-sqlcommenter.git
abort: 'https://github.com/iand675/hs-sqlcommenter.git' does not appear to be an hg repository:
---%<--- (text/html; charset=utf-8)
...
```
---
 cabal2nix/src/Distribution/Nixpkgs/Fetch.hs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/cabal2nix/src/Distribution/Nixpkgs/Fetch.hs b/cabal2nix/src/Distribution/Nixpkgs/Fetch.hs
index 1f2891e0c..0bbd7b9a5 100644
--- a/cabal2nix/src/Distribution/Nixpkgs/Fetch.hs
+++ b/cabal2nix/src/Distribution/Nixpkgs/Fetch.hs
@@ -236,6 +236,8 @@ fetchWith (supportsRev, kind) source = do
          : [ sourceRevision source | supportsRev ]
          ++ hashToList (sourceHash source)
 
+  liftIO $ hPutStrLn stderr $ "$ " ++ unwords (script:args)
+
   MaybeT $ liftIO $ do
     envs <- getEnvironment
     (Nothing, Just stdoutH, _, processH) <-