haskellPackages: add script to sweep for unused overrides

maintainers/scripts/haskell/report-successes.sh

@@ -0,0 +1,39 @@
+set -euo pipefail
+
+function help {
+cat <<END_HELP
+Usage: $0
+
+Call nix-build on derivations passed in standard input and report the ones with successful output paths
+Can be used in combination with ./sweep-packages.nix to search for unnecessary property overrides by attempting builds with the default value
+
+Examples:
+  $0 /nix/store/123-hello.drv /nix/store/456-cowsay.drv
+  nix-instantiate sweep-packages.nix -A derivationsWithout.overrideCabal.jailbreak | $0
+END_HELP
+exit 1
+}
+
+if [[ $# > 0 ]]; then
+    help
+fi
+
+echo "Reading derivations list"
+derivations=$(</dev/stdin)
+echo "Attempting build - successful derivations will be reported at the end"
+echo "To skip to current results press ctrl-c"
+nix-build --keep-going $derivations > /dev/null || : # ignore error code here so we can report successes
+
+echo "Checking which derivations actually placed output paths in the store..."
+for drv in $derivations; do
+    outputs=$(nix-store --query $drv)
+    failures=false;
+    for out in $outputs; do
+        if [[ ! -d $out ]]; then
+            failures=true
+        fi;
+    done;
+    if ! $failures; then
+        echo $drv
+    fi;
+done

maintainers/scripts/haskell/sweep-packages.nix

@@ -0,0 +1,83 @@
+# Utils for sweeping through packages based on some property discoverable at eval time
+# Useful for narrowing down package candidates on which to test some build time property
+#
+# Example 1: finding packages with patches that no longer apply
+#   nix-build sweep-packages.nix -A derivationsWith.overrideAttrs.patches --keep-going
+# The desired packages are reported in the error message or on a subsequent `--dry-run`
+#
+# Example 2: finding packages with unnecessarily disabled test suite
+#   nix-instantiate sweep-packages.nix -A derivationsWithout.overrideAttrs.doCheck | ./report-successes.sh
+# Here we use `derivationsWithout` to reset the `doCheck` override and then look at builds that *don't* fail
+
+{
+  nixpkgs ? import ../../.. { }, # nixpkgs to obtain utils from
+  pkgs ? nixpkgs.haskellPackages, # package set to sweep
+}:
+
+with nixpkgs;
+
+rec {
+  inherit pkgs lib;
+
+  id = x: x;
+
+  canEval = v: (builtins.tryEval v.outPath).success;
+
+  isValidPackage =
+    n: v:
+    lib.all id [
+      (n != "ghc")
+      (!(v.meta.broken or true))
+      ((v.meta.hydraPlatforms or null) != [ ])
+    ];
+
+  original = lens: lib.filterAttrs (n: v: isValidPackage n v && lens.get v) pkgs;
+
+  modified =
+    modify: lens:
+    lib.pipe (original lens) [
+      (builtins.mapAttrs (_: modify lens))
+      (lib.filterAttrs (_: canEval))
+    ];
+
+  lenses = {
+    overrideAttrs = {
+      doCheck = rec {
+        get = v: !(v.doCheck or true);
+        set = x: v: v.overrideAttrs { doCheck = x; };
+        reset = set true;
+      };
+
+      patches = rec {
+        get = v: v.patches != [ ];
+        set = x: v: v.overrideAttrs { patches = x; };
+        reset = set [ ];
+      };
+    };
+
+    overrideCabal = with haskell.lib.compose; {
+      doHaddock = rec {
+        get = v: v.isHaskellLibrary && !(lib.hasInfix "Setup haddock" v.haddockPhase);
+        set = x: overrideCabal { doHaddock = x; };
+        reset = set true;
+      };
+
+      jailbreak = rec {
+        get = v: lib.hasInfix "jailbreak-cabal" v.postPatch;
+        set = x: overrideCabal { jailbreak = x; };
+        reset = set false;
+      };
+
+      enableParallelBuilding = rec {
+        get = v: !lib.hasInfix "-j$NIX_BUILD_CORES" v.setupCompilerEnvironmentPhase;
+        set = x: overrideCabal { enableParallelBuilding = x; };
+        reset = set true;
+      };
+    };
+  };
+
+  sweep = f: builtins.mapAttrs (_: builtins.mapAttrs (_: modified f)) lenses;
+
+  derivationsWithout = sweep (l: l.reset);
+  derivationsWith = sweep (_: id);
+}