Failed attempts at shrinking the size of sqitchPg closure in Nix

NOTES.txt

Attempt 1: Build sqitch with pp

-> built binary still failed with "Can't locate PAR.pm in @INC"

Attemp 2: Install sqitchModule with ./Build bundle

-> Configuring DBD::Pg fails:

> Configuring DBD-Pg-3.10.4 ... N/A
> ! No MYMETA file is found after configure. Your toolchain is too old?
> ! Configure failed for DBD-Pg-3.10.4. See /run/user/1000/nix-build-perl5.30.0-App-Sqitch-1.0.0.drv-3/App-Sqitch-v1.0.0/cpanm/work/1584732411.27638/build.log for details.

It uses cpanm to download modules during build, so it won't work with sandboxed builds anyways.

PAR-Packer.diff

diff --git a/myldr/Makefile.PL b/myldr/Makefile.PL
index 6abee6e..4956025 100644
--- a/myldr/Makefile.PL
+++ b/myldr/Makefile.PL
@@ -60,7 +60,8 @@ my $o = $Config{obj_ext};
 my $gccversion = $Config{gccversion};
 # NOTE: on some platforms, ccopts or ldopts may contain newlines
 chomp( my $pccflags = ccopts() );
-chomp( my $pldflags = ldopts() );
+my @nix_ldflags = split " ", $ENV{'NIX_LDFLAGS'};
+chomp( my $pldflags = ldopts(0,"",\@nix_ldflags) );
 my $dynperl = $Config{useshrplib} && ($Config{useshrplib} ne 'false');
 
 $dynperl = 1 if $pldflags =~ /\B-lperl\b/; # Gentoo lies to us!
diff --git a/myldr/boot.c b/myldr/boot.c
index 55dedab..8812156 100644
--- a/myldr/boot.c
+++ b/myldr/boot.c
@@ -33,7 +33,7 @@ typedef struct
  * return EXTRACT_ALREADY if the extracted file already exists (and has the
  * expected size), EXTRACT_OK if successful, EXTRACT_FAIL otherwise
  */
-static 
+static
 int extract_embedded_file(embedded_file_t *emb_file, const char* ext_name, const char* stmpdir, char** ext_path) {
     int fd;
     chunk_t *chunk;
@@ -48,20 +48,27 @@ int extract_embedded_file(embedded_file_t *emb_file, const char* ext_name, const
         return EXTRACT_ALREADY; /* file already exists and has the expected size */
 
     tmp_path = malloc(len + 1 + 20 + 1); /* 20 decimal digits should be enough to hold up to 2^64-1 */
-    sprintf(tmp_path, "%s.%lu", *ext_path, (unsigned long)getpid());
+    sprintf(tmp_path, "%s.%lu", stmpdir, (unsigned long)getpid());
 
     fd = open(tmp_path, O_CREAT | O_WRONLY | OPEN_O_BINARY, 0755);
-    if ( fd == -1 ) 
+    if ( fd == -1 )  {
+        fprintf(stderr, "boot: open failed %s)\n",
+                tmp_path);
         return EXTRACT_FAIL;
+    }
 
     chunk = emb_file->chunks;
     while (chunk->len) {
-        if ( write(fd, chunk->buf, chunk->len) != chunk->len ) 
+      if ( write(fd, chunk->buf, chunk->len) != chunk->len )  {
+        fprintf(stderr, "boot: write failed)\n");
             return EXTRACT_FAIL;
+      }
         chunk++;
     }
-    if (close(fd) == -1)
+    if (close(fd) == -1) {
+        fprintf(stderr, "boot: close failed)\n");
         return EXTRACT_FAIL;
+    }
 
     chmod(tmp_path, 0750);
     if (rename(tmp_path, *ext_path) == -1)

sqitch-module.nix

self: super:
{
  perlPackages = super.perlPackages // {
    AppSqitch = super.perlPackages.AppSqitch.overrideAttrs (old: {
      installPhase = ''
        runHook preInstall
        mkdir cpanm
        export PERL_CPANM_HOME=$(pwd)/cpanm
        ./Build bundle --install_base $out --with postgres
        runHook postInstall
      '';
      buildInputs = [ super.perlPackages.MenloLegacy ] ++ old.buildInputs;
    });
  };
}

sqitchPg.nix

self: super:
let
  PAR = super.buildPerlPackage rec {
    pname = "PAR";
    version = "1.016";
    src = super.fetchurl {
      url = "mirror://cpan/authors/id/R/RS/RSCHUPP/${pname}-${version}.tar.gz";
      sha256 = "15wxvm27di5yv2mp4wa5kdsfgw0d1175y440m30r5bk76fpzn98a";
    };
    buildInputs = [
      self.perlPackages.ArchiveZip
      self.perlPackages.AutoLoader
      self.perlPackages.CompressZlib
      self.perlPackages.DigestSHA
      self.perlPackages.FileTemp
      self.perlPackages.PARDist
    ];
  };
  pp = super.buildPerlPackage rec {
    pname = "PAR-Packer";
    version = "1.050";
    src = super.fetchurl {
      url = "mirror://cpan/authors/id/R/RS/RSCHUPP/${pname}-${version}.tar.gz";
      sha256 = "1zfwb6x8gjz2f8nm18l3hchpxixhzpbsj97lhsdvsmmw8pdqlxp3";
    };
    buildInputs = [
      self.perlPackages.ArchiveZip
      self.perlPackages.GetoptArgvFile
      self.perlPackages.IPCRun3
      self.perlPackages.ModuleScanDeps
      self.perlPackages.PARDist
      PAR
    ];
    patches = [ ./PAR-Packer.diff ];
  };
in
{
  sqitchPg = super.stdenv.mkDerivation {
    inherit (super.sqitchPg) name;
    src = super.sqitchPg;
    buildPhase = ''
      ${pp}/bin/pp -o bin/sqitch-standalone bin/.sqitch-wrapped
    '';
    installPhase = ''
      mkdir -p $out/bin
      install bin/sqitch-standalone $out/bin/sqitch
    '';
  };
}