2 files changed, 104 insertions, 19 deletions
diff --git a/Biz/Bild/Builder.nix b/Biz/Bild/Builder.nix
index 04002d0..214c110 100644
--- a/Biz/Bild/Builder.nix
+++ b/Biz/Bild/Builder.nix
@@ -1,33 +1,88 @@
-{ srcs # list of files
+/*
+This is the library of nix builders. Some rules to follow:
+- Keep this code as minimal as possible. I'd rather write Haskell than Nix,
+  wouldn't you?
+- Try to reuse as much upstream Nix as possible.
+- Path-like args such as 'srcs' should always be absolute paths.
+*/
+{ srcs ? "" # list of all source files, as a space-separated string
+, main # the entrypoint or main module (not a path)
 , root # path to git root
 , packageSet # name mapped to private.${packageSet}, e.g. 'ghcWith'
-, langDeps ? null # list of deps (as a string), split and passed to packageSet
+, langdeps ? null # list of deps (as a string), split and passed to packageSet
+, sysdeps ? null
 , name # exe name
-, buildPhase
+, compileLine ? "" # Target.compiler <> Target.compilerFlags
 }:
 with import (/. + root + "/Biz/Bild.nix") {};
 with builtins;
 let
-  srcs_ = lib.strings.splitString " " srcs;
+  srcs_ = (lib.strings.splitString " " srcs) ++ [main];
+
   skip = ["_" ".direnv"];
   filter = file: type:
     if elem (baseNameOf file) skip then false
-    # TODO: this means any new directory will cause a rebuild. this bad.
-    # i should recurse into the directory and match against the srcsr
+    # TODO: this means any new directory will cause a rebuild. this bad.  i
+    # should recurse into the directory and match against the srcs. for now I
+    # just use postUnpack to delete empty dirs
     else if type == "directory" then true
-    else if type == "regular" then builtins.elem file srcs_
+    else if type == "regular" then (builtins.elem file srcs_)
     else false;
-   deps = pkgset:
-     if langDeps != null then
-       private.selectAttrs (lib.strings.splitString " " langDeps) pkgset
-     else
-       [];
-in stdenv.mkDerivation rec {
-  inherit name buildPhase;
+
+  # clean up empty dirs
+  postUnpack = "find . -type d -empty -delete";
+
   src = lib.sources.cleanSourceWith {inherit filter; src = lib.sources.cleanSource root;};
-  BIZ_ROOT = src;
-  buildInputs = [ (private.${packageSet} deps) ];
-  installPhase = ''
-    mkdir -p $out/bin && cp ${name} $out/bin
-  '';
+
+  langdeps_ = pkgset:
+    if langdeps == null || langdeps == [] then
+      []
+    else
+      private.selectAttrs (lib.strings.splitString " " langdeps) pkgset;
+  sysdeps_ =
+    if sysdeps == null || sysdeps == [] then
+      []
+    else
+      private.selectAttrs (lib.strings.splitString " " sysdeps) private.nixpkgs.pkgs;
+  BIZ_ROOT = ".";
+in {
+  base = stdenv.mkDerivation rec {
+    inherit name src BIZ_ROOT postUnpack;
+    buildInputs = [ (private.${packageSet} langdeps_) ] ++ sysdeps_;
+    installPhase = "install -D ${name} $out/bin/${name}";
+    buildPhase = compileLine;
+  };
+
+  python = buildPythonApplication rec {
+    inherit name src BIZ_ROOT postUnpack;
+    propagatedBuildInputs = [ (private.${packageSet} langdeps_) ] ++ sysdeps_;
+    buildInputs = sysdeps_;
+    checkInputs = [(private.pythonWith (p: with p; [black mypy pylint]))];
+    checkPhase = ''
+      black --quiet --exclude 'setup\.py$' --check .
+      pylint --errors-only .
+      mypy --strict --no-error-summary --exclude 'setup\.py$' .
+      python -m ${main} test
+    '';
+    preBuild = ''
+      # initialize possibly-empty subdirectories as python modules
+      find . -type d -exec touch {}/__init__.py \;
+      # generate a minimal setup.py
+      cat > setup.py << EOF
+      from setuptools import setup, find_packages
+      setup(
+          name='${name}',
+          entry_points={'console_scripts':['${name} = ${main}:main']},
+          version='0.0.0',
+          url='git://simatime.com/biz.git',
+          author='dev',
+          author_email='dev@simatime.com',
+          description='nil',
+          packages=find_packages(),
+          install_requires=[],
+      )
+      EOF
+    '';
+    pythonImportsCheck = [main]; # sanity check
+  };
 }
diff --git a/Biz/Bild/Example.py b/Biz/Bild/Example.py
new file mode 100644
index 0000000..78a8a6a
--- /dev/null
+++ b/Biz/Bild/Example.py
@@ -0,0 +1,30 @@
+# : out example
+# : dep cryptography
+import sys
+from typing import List
+
+from cryptography.fernet import Fernet
+
+
+def cryptic_hello(name: str) -> str:
+    "Example taken from `cryptography` docs."
+    key = Fernet.generate_key()
+    f = Fernet(key)
+    token = f.encrypt(hello(name).encode("utf-8"))
+    ret = f.decrypt(token).decode("utf-8")
+    assert ret == hello(name)
+    return ret
+
+
+def hello(name: str) -> str:
+    return f"Hello {name}"
+
+
+def main() -> None:
+    if "test" in sys.argv:
+        print("testing success")
+    print(cryptic_hello("world"))
+
+
+if __name__ == "__main__":
+    main()