Error message for missing signatures is unclear

[hseg]

Consider the following snippet:

library test
  hs-source-dirs: test
  signatures:     Signature

if instead, the user mistakenly created a signature test/SigTypo.hsig, cabal will give the uninformative error

cabal: Error: Could not find module: Signature with any suffix:
["gc","chs","hsc","x","y","ly","cpphs","hs","lhs","hsig","lhsig"]. If the
module is autogenerated it should be added to 'autogen-modules'.

Surely some more information could be given? Compare this to the error messages for missing main-is files:

cabal-3.2.0.0: can't find source for ExecTypo in dir

cabal: repl failed for exe:runner from project-0.1.0.0.

and for missing modules:

cabal-3.2.0.0: can't find source for LibTypo in dir,

Also, some highlighting to make the errors pop out from the informational output would be nice.

[phadej]

If I do cabal sdist, for missing exposed-modules I get:

% cabal sdist
cabal: Error: Could not find module: System.Random.SplitMix324 with any
suffix: ["gc","chs","hsc","x","y","ly","cpphs","hs","lhs","hsig","lhsig"]. If
the module is autogenerated it should be added to 'autogen-modules'.

---

If I do cabal build I get

% cabal build libs
Build profile: -w ghc-8.6.5 -O1
In order, the following will be built (use -v for more details):
 - splitmix-0.1.0.3 (lib) (first run)
Configuring library for splitmix-0.1.0.3..
Preprocessing library for splitmix-0.1.0.3..
cabal: can't find source for System/Random/SplitMix324 in src, src-compat,

---

If I do cabal sdist for missing signature

% cabal sdist
cabal: Error: Could not find module: Sig with any suffix:
["gc","chs","hsc","x","y","ly","cpphs","hs","lhs","hsig","lhsig"]. If the
module is autogenerated it should be added to 'autogen-modules'.

---

If I do cabal build I get

% cabal build libs
Resolving dependencies...
Error:
    Non-library component has unfilled requirements: Sig

---

It looks like that cabal-install (3.4) is somewhat consistent,
where build error is an error from GHC (or Backpack instantiator logic).

[zlonast]

@jappeace Can we close this?

[jappeace]

yes