refactor: bunpen: config/translate_opts: make the autodetect logic not pollute the hardcoded path ingestion quite so much

pkgs/additional/bunpen/config/translate_opts.ha

@@ -1,6 +1,7 @@
 // vim: set shiftwidth=2 :
 // ingest literal `cli_opts` into a more computer-friendly form
 
+use errors;
 use errors::ext;
 use fs;
 use log;
@@ -89,17 +90,38 @@ export fn ingest_cli_opts(opts: cli_opts) (cli_request | help) = {
 // if `allow_abs`, then paths with start with `/` are treated as absolute,
 // instead of as relative to `base`.
 fn ingest_paths(into: *[]path::buffer, from: []str, base: (str | void), allow_abs: bool = false, method: (void | autodetect) = void) void = {
+  // enforce file mode requirements as per autodetect (if specified)
+  let (allow_nonexistent, allow_file, allow_dir, allow_parent) = match (method) {
+    case void => yield (true, true, true, false);
+    case let detect: autodetect => yield switch (detect) {
+      case autodetect::EXISTING => yield (false, true, true, false);
+      case autodetect::EXISTING_FILE => yield (false, true, false, false);
+      case autodetect::EXISTING_FILE_OR_PARENT => yield (false, true, false, true);
+      case autodetect::EXISTING_OR_PARENT => yield (false, true, true, true);
+      case autodetect::PARENT => yield (false, false, false, true);
+    };
+  };
+
   for (let path_str .. from) {
     errors::ext::swallow("[config/path] omitting path {}",
-      try_as_path(into, path_str, base, allow_abs, method),
+      try_as_path(into, path_str, base, allow_abs, allow_nonexistent, allow_file, allow_dir, allow_parent),
       path_str
     );
   };
 };
 
-// consider the `path_arg` in the context of the autodetect `method`, and append
-// either that path, its parent, or neither.
-fn try_as_path(into: *[]path::buffer, path_arg: str, base: (str | void), allow_abs: bool, method: (void | autodetect)) (void | fs::error | path::error) = {
+// consider the `path_arg` in the context of the `allow_*` restrictions,
+// and append either that path, its parent, or neither.
+fn try_as_path(
+  into: *[]path::buffer,
+  path_arg: str,
+  base: (str | void),
+  allow_abs: bool,
+  allow_nonexistent: bool,
+  allow_file: bool,
+  allow_dir: bool,
+  allow_parent: bool,
+) (void | fs::error | path::error) = {
   let path_buf = if (allow_abs && path::abs(path_arg)) {
     yield path::init(path_arg)?;
   } else match (base) {
@@ -109,48 +131,38 @@ fn try_as_path(into: *[]path::buffer, path_arg: str, base: (str | void), allow_a
       return path::not_prefix;
   };
 
-  // enforce file mode requirements as per autodetect (if specified),
-  // possibly changes `path_buf` to point to its parent.
-  match (method) {
-    case void => void;
-    case let detect: autodetect => switch (detect) {
-      case autodetect::EXISTING =>
-        check_exists(&path_buf, true)?;
-      case autodetect::EXISTING_FILE =>
-        check_exists(&path_buf, false)?;
-      case autodetect::EXISTING_FILE_OR_PARENT =>
-        match (check_exists(&path_buf, false)) {
-          case void => void;
-          case =>
-            path::push(&path_buf, "..")?;
-            check_exists(&path_buf, true)?;
-        };
-      case autodetect::EXISTING_OR_PARENT =>
-        match (check_exists(&path_buf, true)) {
-          case void => void;
-          case =>
-            path::push(&path_buf, "..")?;
-            check_exists(&path_buf, true)?;
-        };
-      case autodetect::PARENT =>
-        path::push(&path_buf, "..")?;
-        check_exists(&path_buf, true)?;
-    };
+  if (allow_nonexistent)
+    return append(into, path_buf);
+
+  // try the path
+  let err = match (check_exists(&path_buf, allow_file, allow_dir)) {
+    case void => return append(into, path_buf);
+    case let err: (fs::error | path::error) => yield err;
   };
 
-  append(into, path_buf);
+  // try the parent
+  if (allow_parent) {
+    path::push(&path_buf, "..")?;
+    check_exists(&path_buf, false, true)?;
+    return append(into, path_buf);
+  };
+  return err;
 };
 
 // ensure that the specified path exists.
 // if it exists but not as a directory, succeed only if `dir_ok = true`.
-fn check_exists(pathbuf: *path::buffer, dir_ok: bool) (void | fs::error | path::error)  = {
+fn check_exists(pathbuf: *path::buffer, file_ok: bool, dir_ok: bool) (void | fs::error | path::error)  = {
+  if (!file_ok && !dir_ok)
+    return errors::invalid;  // save a syscall for `--bunpen-autodetect parent`
+
   // stat the path. in case of symlinks dereference to the underlying entity.
   let dereferenced = fs::realpath(os::cwd, path::string(pathbuf))?;
   let stat = fs::stat(os::cwd, dereferenced)?;
   let is_dir = (stat.mode & rt::S_IFDIR) != 0;
 
-  if (is_dir && !dir_ok) {
-    log::printfln("[config/path/try] not adding path (wanted a file, but this is a directory): {}", path::string(pathbuf));
+  if (is_dir && dir_ok || !is_dir && file_ok)
+    return
+
+  log::printfln("[config/path/try] not adding path (exists, but as wrong type): {}", path::string(pathbuf));
   return fs::wrongtype;
 };
-};