texdoc: install zsh completion

pkgs/tools/typesetting/tex/texlive/default.nix

@@ -4,7 +4,7 @@
 */
 { stdenv, lib, fetchurl, runCommand, writeText, buildEnv
 , callPackage, ghostscript_headless, harfbuzz
-, makeWrapper
+, makeWrapper, installShellFiles
 , python3, ruby, perl, tk, jdk, bash, snobol4
 , coreutils, findutils, gawk, getopt, gnugrep, gnumake, gnupg, gnused, gzip, ncurses, zip
 , libfaketime, asymptote, biber-ms, makeFontsConf
@@ -376,6 +376,8 @@ let
         extraRevision = "-tlpdb${toString tlpdbVersion.revision}";
         extraVersion = "-tlpdb-${toString tlpdbVersion.revision}";
 
+        extraNativeBuildInputs = [ installShellFiles ];
+
         # build Data.tlpdb.lua (part of the 'tlType == "run"' package)
         postUnpack = ''
           if [[ -f "$out"/scripts/texdoc/texdoc.tlu ]]; then
@@ -392,6 +394,18 @@ let
             cp texdoc/cache-tlpdb.lua "$out"/scripts/texdoc/Data.tlpdb.lua
           fi
         '';
+
+        # install zsh completion
+        postFixup = ''
+          TEXMFCNF="${bin.core}"/share/texmf-dist/web2c TEXMF="$scriptsFolder/../.." \
+            texlua "$out"/bin/texdoc --print-completion zsh > "$TMPDIR"/_texdoc
+          substituteInPlace "$TMPDIR"/_texdoc \
+            --replace 'compdef __texdoc texdoc' '#compdef texdoc' \
+            --replace '$(kpsewhich -var-value TEXMFROOT)/tlpkg/texlive.tlpdb' '$(kpsewhich Data.tlpdb.lua)' \
+            --replace '/^name[^.]*$/ {print $2}' '/^  \["[^"]*"\] = {$/ { print substr($1,3,length($1)-4) }'
+          echo '__texdoc' >> "$TMPDIR"/_texdoc
+          installShellCompletion --zsh "$TMPDIR"/_texdoc
+        '';
       };
 
       "texlive.infra" = {