Improve error message on bad working directory

Handles two cases:

- working directory doesn't exist.
- working directory cannot be changed into due to on of the following:
    - The process lacks permissions to view the contents.
    - The path points at a non-directory file.

Addresses: casey#2295

src/error.rs

@@ -127,6 +127,11 @@ pub(crate) enum Error<'src> {
   MissingModuleFile {
     module: Name<'src>,
   },
+  WorkingDirectoryIo {
+    recipe: &'src str,
+    working_directory: PathBuf,
+    io_error: io::Error,
+  },
   NoChoosableRecipes,
   NoDefaultRecipe,
   NoRecipes,
@@ -470,6 +475,12 @@ impl<'src> ColorDisplay for Error<'src> {
       UnstableFeature { unstable_feature } => {
         write!(f, "{unstable_feature} Invoke `just` with `--unstable`, set the `JUST_UNSTABLE` environment variable, or add `set unstable` to your `justfile` to enable unstable features.")?;
       }
+      WorkingDirectoryIo { recipe, working_directory, io_error } => {
+        match io_error.kind() {
+          io::ErrorKind::NotFound => write!(f, "Recipe `{recipe}` could not be run because just could not find working directory `{}`: {io_error}", working_directory.to_string_lossy()),
+          _ => write!(f, "Recipe `{recipe}` could not be run because just could not set working directory to `{}`: {io_error}", working_directory.to_string_lossy()),
+        }?;
+      },
       WriteJustfile { justfile, io_error } => {
         let justfile = justfile.display();
         write!(f, "Failed to write justfile to `{justfile}`: {io_error}")?;

src/recipe.rs

@@ -304,6 +304,15 @@ impl<'src, D> Recipe<'src, D> {
           }
         }
         Err(io_error) => {
+          if let Some(working_directory) = self.working_directory(context) {
+            if let Err(io_error) = fs::read_dir(working_directory.clone()) {
+              return Err(Error::WorkingDirectoryIo {
+                recipe: self.name(),
+                working_directory,
+                io_error,
+              });
+            }
+          }
           return Err(Error::Io {
             recipe: self.name(),
             io_error,

tests/working_directory.rs

@@ -1,4 +1,4 @@
-use super::*;
+use {super::*, fs::Permissions, std::os::unix::fs::PermissionsExt};
 
 const JUSTFILE: &str = r#"
 foo := `cat data`
@@ -331,3 +331,61 @@ file := shell('cat file.txt')
     .stdout("FILE\n")
     .run();
 }
+
+#[test]
+fn missing_working_directory_produces_clear_message() {
+  Test::new()
+    .justfile(
+      "
+      set working-directory := 'missing'
+      default:
+        pwd
+    ",
+    )
+    .status(1)
+    .stderr_regex(
+      ".*Recipe `default` could not be run because just could not find working directory `.*/missing`.*",
+    )
+    .run();
+}
+
+#[test]
+fn unusable_working_directory_produces_clear_message() {
+  Test::new()
+  .justfile(
+    "
+    set working-directory := 'unusable'
+    default:
+      pwd
+  ",
+  )
+  .tree(tree! {
+    unusable: {}
+  })
+  .chmod("unusable", Permissions::from_mode(0o000))
+  .status(1)
+  .stderr_regex(
+    ".*Recipe `default` could not be run because just could not set working directory to `.*/unusable`:.*",
+  )
+  .run();
+}
+
+#[test]
+fn working_directory_is_not_a_directory_produces_clear_message() {
+  Test::new()
+  .justfile(
+    "
+    set working-directory := 'unusable'
+    default:
+      pwd
+  ",
+  )
+  .tree(tree! {
+    unusable: "is not a directory"
+  })
+  .status(1)
+  .stderr_regex(
+    ".*Recipe `default` could not be run because just could not set working directory to `.*/unusable`:.*",
+  )
+  .run();
+}