Switch excludes to be Option like exclusives

src/args.rs

@@ -26,14 +26,8 @@ pub struct Args {
     pub min_count: u64,
 
     /// Exclude any words from a comma-delimited list.
-    #[arg(
-        short,
-        long,
-        default_value = "",
-        use_value_delimiter = true,
-        value_name = "WORDS"
-    )]
-    pub exclude: Vec<String>,
+    #[arg(short, long, use_value_delimiter = true, value_name = "WORDS")]
+    pub exclude: Option<Vec<String>>,
 
     /// Only include words from a comma-delimited list.
     #[arg(short = 'O', long, use_value_delimiter = true, value_name = "WORDS")]

src/lib.rs

@@ -176,11 +176,11 @@ impl From<u64> for MinCount {
 
 /// A list of words that should not be tallied.
 #[derive(Clone, Debug, Default, Eq, PartialEq, PartialOrd, Ord, Hash)]
-pub struct WordsExclude(pub Vec<String>);
+pub struct WordsExclude(pub Option<Vec<String>>);
 
 impl From<Vec<String>> for WordsExclude {
     fn from(raw: Vec<String>) -> Self {
-        Self(raw)
+        Self(Some(raw))
     }
 }
 
@@ -279,13 +279,13 @@ impl WordTally {
         }
 
         // Remove any words on the `exclude` word list.
-        let normalized_excludes: Vec<_> = filters
-            .words_exclude
-            .0
-            .iter()
-            .map(|exclude| Self::normalize_case(exclude, case))
-            .collect();
-        tally_map.retain(|word, _| !normalized_excludes.contains(word));
+        if let Some(excludes) = filters.words_exclude.0 {
+            let normalized_excludes: Vec<_> = excludes
+                .iter()
+                .map(|exclude| Self::normalize_case(exclude, case))
+                .collect();
+            tally_map.retain(|word, _| !normalized_excludes.contains(word));
+        }
 
         // Remove any words absent from the `only` word list.
         if let Some(exclusives) = filters.words_only.0 {

tests/lib.rs

@@ -293,7 +293,7 @@ fn test_excluding_words() {
     let input = "The tree that would grow to heaven must send its roots to hell.".as_bytes();
     let excluded_words = vec!["Heaven".to_string(), "Hell".to_string()];
     let filters = Filters {
-        words_exclude: WordsExclude(excluded_words),
+        words_exclude: WordsExclude(Some(excluded_words)),
         ..Filters::default()
     };
     let tally = WordTally::new(input, Case::Lower, Sort::Unsorted, filters);
@@ -346,7 +346,10 @@ fn test_min_count_from() {
 #[test]
 fn test_words_exclude_from() {
     let excluded = vec!["beep".to_string(), "boop".to_string()];
-    assert_eq!(WordsExclude::from(excluded.clone()), WordsExclude(excluded));
+    assert_eq!(
+        WordsExclude::from(excluded.clone()),
+        WordsExclude(Some(excluded))
+    );
 }
 
 #[test]