From dd17326bccd802c075c26426292f1b593344fe73 Mon Sep 17 00:00:00 2001
From: Teo Camarasu <teo.camarasu@tracsis.com>
Date: Wed, 24 Apr 2024 11:47:53 +0100
Subject: [PATCH] Downgrade NoLibraryFound from an error to a warning

This makes Setup copy/install succeed if there's
nothing to do because the package doesn't contain
a library or executable.

This allows downstream users of Cabal to avoid having to
add workarounds for this edge case.

Resolves #6750
---
 Cabal/src/Distribution/Simple/Errors.hs  |  2 +-
 Cabal/src/Distribution/Simple/Install.hs |  2 +-
 changelog.d/issue-6750                   | 13 +++++++++++++
 3 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 changelog.d/issue-6750

diff --git a/Cabal/src/Distribution/Simple/Errors.hs b/Cabal/src/Distribution/Simple/Errors.hs
index 45029565e99..a4ee3ea2da2 100644
--- a/Cabal/src/Distribution/Simple/Errors.hs
+++ b/Cabal/src/Distribution/Simple/Errors.hs
@@ -47,7 +47,7 @@ data CabalException
   | EnableBenchMark
   | BenchMarkNameDisabled String
   | NoBenchMark String
-  | NoLibraryFound
+  | NoLibraryFound -- ^ @NoLibraryFound@ has been downgraded to a warning, and is therefore no longer emitted.
   | CompilerNotInstalled CompilerFlavor
   | CantFindIncludeFile String
   | UnsupportedTestSuite String
diff --git a/Cabal/src/Distribution/Simple/Install.hs b/Cabal/src/Distribution/Simple/Install.hs
index c1134e2b355..c46f28b3529 100644
--- a/Cabal/src/Distribution/Simple/Install.hs
+++ b/Cabal/src/Distribution/Simple/Install.hs
@@ -147,7 +147,7 @@ install_setupHooks
 
       checkHasLibsOrExes =
         unless (hasLibs pkg_descr || hasForeignLibs pkg_descr || hasExes pkg_descr) $
-          dieWithException verbosity NoLibraryFound
+          warn verbosity "No executables and no library found. Nothing to do."
 
 -- | Copy package global files.
 copyPackage
diff --git a/changelog.d/issue-6750 b/changelog.d/issue-6750
new file mode 100644
index 00000000000..f6fcb860f8f
--- /dev/null
+++ b/changelog.d/issue-6750
@@ -0,0 +1,13 @@
+synopsis: Make Setup copy/install succeed when there's no executable or library
+packages: Cabal
+prs: TODO
+issues: #750
+
+description: {
+  Historically the Setup copy and install steps would fail if the package didn't
+  contain an executable or library component. In this case there's nothing to do.
+
+  This required workarounds for downstream users of Cabal to handle this edge case.
+  Now we downgrade this error to a warning. Cabal will now succeed if there's 
+  nothing to do.
+}