Update cabal/nix build code for bench-report

benchmark/README.md

@@ -85,6 +85,13 @@ report from the results using the `bench-show` package. Try `bench.sh
 
 ## bench.sh: Quick start
 
+IMPORTANT NOTE: If you are using nix then you can use `--use-nix`
+flag so that the `bench-report` executable is built using nix. That
+can save a lot of time compiling it. However, once it is built it
+will be cached in the `bin` directory of the repo and used from there
+every time. You can also build it manually from the cabal file in
+`benchmark/bench-report` and install it in the `bin` directory.
+
 Run the default benchmark suites:
 
 ```

benchmark/bench-report/cabal.project

@@ -1 +1 @@
-packages: benchmark/bench-report/bench-report.cabal
+packages: .

benchmark/bench-report/default.nix

@@ -1,30 +1,50 @@
-{ nixpkgs ? import <nixpkgs> {}, compiler ? "default", doBenchmark ? false }:
+{
+  nixpkgs ?
+    # nixpkgs 21.05 needs a revised version of bench-show and we do not
+    # know how to use a revised version in nix.
+    #import (builtins.fetchTarball https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz)
+    import (builtins.fetchTarball https://github.com/composewell/nixpkgs/archive/01dd2b4e738.tar.gz)
+        {}
+#, compiler ? "ghc884" # For nix 21.05
+, compiler ? "default"
+}:
+let haskellPackages =
+        if compiler == "default"
+        then nixpkgs.haskellPackages
+        else nixpkgs.haskell.packages.${compiler};
 
-let
+    mkPackage = super: pkg: path: opts: inShell:
+                let orig = super.callCabal2nixWithOptions pkg path opts {};
+                 in if inShell
+                    # Avoid copying the source directory to nix store by using
+                    # src = null.
+                    then orig.overrideAttrs (oldAttrs: { src = null; })
+                    else orig;
 
-  inherit (nixpkgs) pkgs;
+    mkHaskellPackages = inShell:
+        haskellPackages.override {
+            overrides = self: super:
+                with nixpkgs.haskell.lib;
+                {
+                    bench-report = mkPackage super "bench-report" ./. "" inShell;
+                };
+        };
 
-  f = { mkDerivation, base, bench-show, stdenv, transformers }:
-      mkDerivation {
-        pname = "bench-report";
-        version = "0.0.0";
-        src = ./.;
-        isLibrary = false;
-        isExecutable = true;
-        executableHaskellDepends = [ base bench-show transformers ];
-        description = "Benchmark report generation";
-        license = "unknown";
-        hydraPlatforms = stdenv.lib.platforms.none;
-      };
+    drv = mkHaskellPackages true;
 
-  haskellPackages = if compiler == "default"
-                       then pkgs.haskellPackages
-                       else pkgs.haskell.packages.${compiler};
-
-  variant = if doBenchmark then pkgs.haskell.lib.doBenchmark else pkgs.lib.id;
-
-  drv = variant (haskellPackages.callPackage f {});
-
-in
-
-  if pkgs.lib.inNixShell then drv.env else drv
+    shell = drv.shellFor {
+        packages = p:
+          [ p.bench-report
+          ];
+        # Use a better prompt
+        shellHook = ''
+          export CABAL_DIR="$(pwd)/.cabal.nix"
+          if test -n "$PS_SHELL"
+          then
+            export PS1="$PS_SHELL\[$bldred\](nix)\[$txtrst\] "
+          fi
+        '';
+    };
+in if nixpkgs.lib.inNixShell
+   then shell
+   else (mkHaskellPackages false).streamly

bin/bench.sh

@@ -21,6 +21,7 @@ print_help () {
   echo "       [--quick]"
   echo "       [--raw]"
   echo "       [--dev-build]"
+  echo "       [--use-nix]"
   echo "       [--with-compiler <compiler exe name>]"
   echo "       [--cabal-build-options <options>]"
   echo "       [--rtsopts <opts>]"
@@ -68,28 +69,13 @@ list_comparisons ()  {
   echo
 }
 
-# chart is expensive to build and usually not required to be rebuilt,
-# use master branch as fallback
+# chart is expensive to build and usually not required to be rebuilt
 cabal_which_report() {
-  local path=$(cabal_which bench-report x $1)
-  if test -z "$path"
-  then
-    echo "Cannot find $1 executable, trying in dist-newstyle" 1>&2
-    local path1=$(cabal_which_builddir dist-newstyle bench-report x $1)
-    if test -z "$path1"
+    local path="./bin/$1"
+    if test -e "$path"
     then
-      local path2="./bin/$1"
-      echo "Cannot find $1 executable, trying $path2" 1>&2
-      if test -e "$path2"
-      then
-        echo $path2
-      fi
-    else
-        echo $path1
+      echo $path
     fi
-  else
-    echo $path
-  fi
 }
 
 find_report_prog() {
@@ -113,8 +99,16 @@ build_report_prog() {
     then
       echo "Building bench-report executables"
       BUILD_ONCE=1
-      $CABAL_EXECUTABLE v2-build bench-report --project-file=benchmark/bench-report/cabal.project \
-        || die "bench-report build failed"
+      pushd benchmark/bench-report
+      local cmd
+      cmd="$CABAL_EXECUTABLE install --installdir ../../bin bench-report"
+      if test "$USE_NIX" -eq 0
+      then
+        $cmd || die "bench-report build failed"
+      else
+        nix-shell --run "$cmd" || die "bench-report build failed"
+      fi
+      popd
 
     elif test ! -x "$prog_path"
     then
@@ -308,6 +302,7 @@ cd $SCRIPT_DIR/..
 
 USE_GAUGE=0
 USE_GIT_CABAL=1
+USE_NIX=0
 set_common_vars
 
 DEFAULT_FIELDS="allocated bytescopied cputime"
@@ -360,6 +355,7 @@ do
     --graphs) GRAPH=1; shift ;;
     --no-measure) MEASURE=0; shift ;;
     --dev-build) RUNNING_DEVBUILD=1; shift ;;
+    --use-nix) USE_NIX=1; shift ;;
     --use-gauge) USE_GAUGE=1; shift ;;
     --) shift; break ;;
     *) echo "Unknown flags: $*"; echo; print_help ;;