Report mixed leading whitespace in recipe bodies

src/lexer.rs

@@ -349,12 +349,12 @@ impl<'src> Lexer<'src> {
       return Ok(());
     }
 
-    let body_whitespace = &whitespace[..whitespace
+    let indentation = whitespace
       .char_indices()
-      .take(self.indentation().chars().count())
-      .map(|(i, _c)| i)
-      .next()
-      .unwrap_or(0)];
+      .nth(self.indentation().chars().count())
+      .map_or(whitespace.len(), |(i, _c)| i);
+
+    let body_whitespace = &whitespace[..indentation];
 
     let spaces = whitespace.chars().any(|c| c == ' ');
     let tabs = whitespace.chars().any(|c| c == '\t');
@@ -2300,8 +2300,8 @@ mod tests {
     offset: 12,
     line:   3,
     column: 0,
-    width:  3,
-    kind:   InconsistentLeadingWhitespace{expected: "\t\t", found: "\t  "},
+    width:  2,
+    kind:   MixedLeadingWhitespace{whitespace: "\t "},
   }
 
   error! {

tests/misc.rs

@@ -861,14 +861,14 @@ fn extra_leading_whitespace() {
 #[test]
 fn inconsistent_leading_whitespace() {
   Test::new()
-    .justfile("bar:\n\t\techo hello\n\t echo goodbye")
+    .justfile("bar:\n\t\techo hello\n\techo goodbye")
     .stderr(
       "error: recipe line has inconsistent leading whitespace, \
-            started with `␉␉` but found line with `␉␠`
+            started with `␉␉` but found line with `␉`
  ——▶ justfile:3:1
   │
-3 │      echo goodbye
-  │ ^^^^^
+3 │     echo goodbye
+  │ ^^^^
 ",
     )
     .failure();
@@ -2667,3 +2667,19 @@ fn windows_interpreter_path_no_base() {
     )
     .success();
 }
+
+#[test]
+fn mixed_whitespace_in_recipe_body() {
+  Test::new()
+    .justfile("bar:\n  echo a\n \techo b")
+    .stderr(
+      "error: found a mix of tabs and spaces in leading whitespace: `␠␉`
+leading whitespace may consist of tabs or spaces, but not both
+ ——▶ justfile:3:1
+  │
+3 │      echo b
+  │ ^^^^^
+",
+    )
+    .failure();
+}