Collapse consecutive hyphens in slugs

Previously, a heading or page called something like 'Name - subtitle'
would become the slug 'name---subtitle' because the hyphen is stuck
between spaces which also become hyphens. This looks silly. The new
function will generate the slug 'name-subtitle' instead.

1 files changed, 13 insertions, 5 deletions

diff --git a/src/string_utils.rs b/src/string_utils.rs
index 2061110..cceb575 100644
--- a/src/string_utils.rs
+++ b/src/string_utils.rs
@@ -66,11 +66,19 @@ impl From<&str> for Name {
 
 // Turn a string into a tidy URL slug.
 pub fn to_slug(text: &str) -> String {
-    text.to_ascii_lowercase().chars().filter_map(|c|
-        if c.is_alphanumeric() || "-_~.+/#".contains(c) { Some(c) }
-        else if c == ' ' { Some('-') }
-        else { None } )
-    .collect()
+    let mut string = String::new();
+    let mut prev = ' ';
+    for c in text.to_lowercase().chars() {
+        let c = match c == ' ' {
+            true => '-',
+            false => c,
+        };
+        if c.is_alphanumeric()     { string.push(c) }
+        if "_~.+/#".contains(c)    { string.push(c) }
+        if c == '-' && prev != '-' { string.push(c) }
+        prev = c;
+    }
+    return string;
 }
 
 // Prevent link hrefs from breaking out of quotations.