Better warnings

Author: hamishmack

overlays/bootstrap.nix

@@ -378,25 +378,27 @@ in {
         })));
 
     # Use this where we still have not good way to choose GHC version
-    defaultCompilerNixNameTODO =
-      # Need to use something from 8.8.x as the default to build aarch64 native compiler:
-      if final.targetPlatform.isAarch64 && final.buildPlatform.isAarch64
-        then "ghc883"
-        else "ghc865";
+    internalDefaultCompilerNixName = "ghc883";
 
     # Use this when we are happy with a general warning
     defaultCompilerNixName = final.haskell-nix.defaultCompilerNixNameWithWarning
-      (default:
-            "WARNING: No compiler nix name specified! "
-          + "Defaulting to ${default}.  "
-          + "Please consider specifying a ghc explicitly.");
+      (default: "Please consider specifying ${default} explicitly.");
 
     #  when we can provide a better message
     defaultCompilerNixNameWithWarning = warning:
       if final.haskell-nix ? userCompilerNixName
-        then final.haskell-nix.userCompilerNixName
-        else __trace (warning final.haskell-nix.defaultCompilerNixNameTODO)
-          final.haskell-nix.defaultCompilerNixNameTODO;
+        then
+          __trace ("WARNING: defaultCompilerNixName is deprecated!  "
+            + warning final.haskell-nix.userCompilerNixName)
+            final.haskell-nix.userCompilerNixName
+        else
+          # Need to use something from 8.8.x as the default to build aarch64 native compiler:
+          let compiler-nix-name =
+            if final.targetPlatform.isAarch64 && final.buildPlatform.isAarch64
+              then "ghc883"
+              else "ghc865";
+          in __trace ("WARNING: No compiler nix name specified!  "
+            + warning compiler-nix-name) compiler-nix-name;
 
     ghc = final.haskell-nix.compiler."${
       final.haskell-nix.defaultCompilerNixNameWithWarning (default:

overlays/haskell.nix

@@ -620,7 +620,9 @@ final: prev: {
 
         # Add this to your tests to make all the dependencies of haskell.nix
         # are tested and cached.
-        haskellNixRoots = final.haskell-nix.roots final.haskell-nix.defaultCompilerNixName;
+        haskellNixRoots = final.haskell-nix.roots (final.haskell-nix.defaultCompilerNixNameWithWarning (default:
+            "Please consider replacing `haskellNixRoots` with `p.roots` on your project "
+          + "or using `haskell-nix.roots \"${default}\"`."));
         roots = compiler-nix-name: final.recurseIntoAttrs {
           Level0 = roots' compiler-nix-name 0;
           Level1 = roots' compiler-nix-name 1;
@@ -629,7 +631,9 @@ final: prev: {
           Level2 = roots' compiler-nix-name 2;
         };
 
-        haskellNixRoots' = final.haskell-nix.roots' final.haskell-nix.defaultCompilerNixName;
+        haskellNixRoots' = final.haskell-nix.roots' (final.haskell-nix.defaultCompilerNixNameWithWarning (default:
+            "Please consider replacing `haskellNixRoots'` with `p.roots'` on your project "
+          + "or using `haskell-nix.roots' \"${default}\"`."));
         roots' = compiler-nix-name: ifdLevel:
           	final.recurseIntoAttrs ({
             # Things that require no IFD to build

overlays/tools.nix

@@ -69,8 +69,8 @@ in { haskell-nix = prev.haskell-nix // {
       args' = final.haskell-nix.haskellLib.versionOrArgsToArgs versionOrArgs;
       args = {
           compiler-nix-name = final.haskell-nix.defaultCompilerNixNameWithWarning (default:
-              "WARNING: No compiler version specified for building the ${name} tool (using ${default}).  "
-            + "Please consider using the `p.tool` or `p.tools` function on your project `p` (they will "
+              "While building the ${name} tool (using ${default}).  "
+            + "Please consider using the `p.tool` or `p.tools` function on your project (they will "
             + "use the same ghc as the project) or using the `tools` argument of `shellFor` or "
             + (if final.lib.isAttrs versionOrArgs
                 then "adding `compiler-nix-name = \"${default}\";`"