More execline experiments & testing

Improves the “execline experience” and adds some basic tests.
The idea is that the final result doesn’t use coreutils and provides a
feasible alternative to bash-based tooling.

2 files changed, 119 insertions, 7 deletions

diff --git a/pkgs/profpatsch/execline/run-execline-tests.nix b/pkgs/profpatsch/execline/run-execline-tests.nix
new file mode 100644
index 00000000..c2c4c23e
--- /dev/null
+++ b/pkgs/profpatsch/execline/run-execline-tests.nix
@@ -0,0 +1,86 @@
+{ stdenv, drvSeqL, runExecline
+, ifCommand, redirfdCommand, s6GrepCommand
+, importasCommand, s6TouchCommand, s6CatCommand
+, execlinebCommand, s6TestCommand, s6ChmodCommand
+# https://www.mail-archive.com/skaware@list.skarnet.org/msg01256.html
+, coreutils }:
+
+# TODO: run all of these locally! runExeclineLocal
+
+let
+
+  # lol
+  writeScript = name: script: runExecline {
+    inherit name;
+    derivationArgs = {
+      inherit script;
+      passAsFile = [ "script" ];
+    };
+    execline = ''
+      importas -ui s scriptPath
+      importas -ui out out
+      foreground {
+        ${coreutils}/bin/mv $s $out
+      }
+      ${s6ChmodCommand} 0755 $out
+    '';
+   };
+
+  # execline block of depth 1
+  block = args: builtins.map (arg: " ${arg}") args ++ [ "" ];
+
+  # derivation that tests whether a given line exists
+  # in the given file. Does not use runExecline, because
+  # that should be tested after all.
+  fileHasLine = line: file: derivation {
+    name = "file-${file.name}-has-line";
+    inherit (stdenv) system;
+    builder = ifCommand;
+    args =
+      (block [
+        redirfdCommand "-r" "0" file   # read file to stdin
+        s6GrepCommand "-F" "-q" line      # and grep for the line
+      ])
+      ++ [
+        # if the block succeeded, touch $out
+        importasCommand "-ui" "out" "out"
+        s6TouchCommand "$out"
+      ];
+  };
+
+  # basic test that touches out
+  basic = runExecline {
+    name = "basic";
+    execline = ''
+      importas -ui out out
+      ${s6TouchCommand} $out
+    '';
+  };
+
+  # whether the stdin argument works as intended
+  stdin = fileHasLine "foo" (runExecline {
+    name = "stdin";
+    stdin = "foo\nbar\nfoo";
+    execline = ''
+      importas -ui out out
+      # this pipes stdout of s6-cat to $out
+      # and s6-cat redirects from stdin to stdout
+      redirfd -w 1 $out ${s6CatCommand}
+    '';
+  });
+
+  wrapWithVar = runExecline {
+    name = "wrap-with-var";
+    builderWrapper = writeScript "var-wrapper" ''
+      #!${execlinebCommand} -S0
+      export myvar myvalue $@
+    '';
+    execline = ''
+      importas -ui v myvar
+      if { ${s6TestCommand} myvalue = $v }
+        importas out out
+        ${s6TouchCommand} $out
+    '';
+  };
+
+in args: drvSeqL [ basic stdin wrapWithVar ] (runExecline args)
diff --git a/pkgs/profpatsch/execline/run-execline.nix b/pkgs/profpatsch/execline/run-execline.nix
index 40915f25..61c8c2e6 100644
--- a/pkgs/profpatsch/execline/run-execline.nix
+++ b/pkgs/profpatsch/execline/run-execline.nix
@@ -1,7 +1,12 @@
-{ stdenv, importasCommand, execlinebCommand }:
+{ stdenv, importasCommand, execCommand, redirfdCommand, execlinebCommand }:
 { name
-# the execline script
+# the execline script as string
 , execline
+# a string to pass as stdin to the execline script
+, stdin ? ""
+# a program wrapping the acutal execline invocation;
+# should be in Bernstein-chaining style
+, builderWrapper ? execCommand
 # additional arguments to pass to the derivation
 , derivationArgs ? {}
 }:
@@ -18,20 +23,41 @@ derivation (derivationArgs // {
 
   # okay, `builtins.toFile` does not accept strings
   # that reference drv outputs. This means we need
-  # to pass the script as envvar;
+  # to pass the script and stdin as envvar;
   # this might clash with another passed envar,
   # so we give it a long & unique name
   _runExeclineScript = execline;
-  passAsFile = [ "_runExeclineScript" ]
-            ++ derivationArgs.passAsFile or [];
+  _runExeclineStdin = stdin;
+  passAsFile = [
+    "_runExeclineScript"
+    "_runExeclineStdin"
+  ] ++ derivationArgs.passAsFile or [];
+
+  # the default, exec acts as identity executable
+  builder = builderWrapper;
 
-  builder = importasCommand;
   args = [
+    importasCommand          # import script file as $script
     "-ui"                    # drop the envvar afterwards
     "script"                 # substitution name
     "_runExeclineScriptPath" # passed script file
+
+    # TODO: can we scrap stdin via builderWrapper?
+    importasCommand          # do the same for $stdin
+    "-ui"
+    "stdin"
+    "_runExeclineStdinPath"
+
+    redirfdCommand           # now we
+    "-r"                     # read the file
+    "0"                      # into the stdin of execlineb
+    "$stdin"                 # that was given via stdin
+
     execlinebCommand         # the actual invocation
-    "-P"                     # ignore command line arguments
+    # TODO: depending on the use-case, -S0 might not be enough
+    # in all use-cases, then a wrapper for execlineb arguments
+    # should be added (-P, -S, -s).
+    "-S0"                    # set $@ inside the execline script
     "-W"                     # die on syntax error
     "$script"                # substituted by importas
   ];