X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Fstring.rs;h=d45f15a1c9bab59cb85710d453c096347cd6a748;hb=6fb188bd43840f4a99c6a4b4cdbdb21ccf3304e7;hp=fd7ac89013a32cba04c94a37bd7cbd2a1bc0df62;hpb=9038da6df0a11a55255a7ea562d91d1e93679252;p=rust.git

diff --git a/src/string.rs b/src/string.rs
index fd7ac89013a..d45f15a1c9b 100644
--- a/src/string.rs
+++ b/src/string.rs
@@ -19,12 +19,19 @@
 
 const MIN_STRING: usize = 10;
 
+/// Describes the layout of a piece of text.
 pub struct StringFormat<'a> {
+    /// The opening sequence of characters for the piece of text
     pub opener: &'a str,
+    /// The closing sequence of characters for the piece of text
     pub closer: &'a str,
+    /// The opening sequence of characters for a line
     pub line_start: &'a str,
+    /// The closing sequence of characters for a line
     pub line_end: &'a str,
+    /// The allocated box to fit the text into
     pub shape: Shape,
+    /// Trim trailing whitespaces
     pub trim_end: bool,
     pub config: &'a Config,
 }
@@ -57,16 +64,21 @@ fn max_chars_with_indent(&self) -> Option<usize> {
 
     /// Like max_chars_with_indent but the indentation is not substracted.
     /// This allows to fit more graphemes from the string on a line when
-    /// SnippetState::Overflow.
+    /// SnippetState::EndWithLineFeed.
     fn max_chars_without_indent(&self) -> Option<usize> {
         Some(self.config.max_width().checked_sub(self.line_end.len())?)
     }
 }
 
-pub fn rewrite_string<'a>(orig: &str, fmt: &StringFormat<'a>) -> Option<String> {
+pub fn rewrite_string<'a>(
+    orig: &str,
+    fmt: &StringFormat<'a>,
+    newline_max_chars: usize,
+) -> Option<String> {
     let max_chars_with_indent = fmt.max_chars_with_indent()?;
     let max_chars_without_indent = fmt.max_chars_without_indent()?;
-    let indent = fmt.shape.indent.to_string_with_newline(fmt.config);
+    let indent_with_newline = fmt.shape.indent.to_string_with_newline(fmt.config);
+    let indent_without_newline = fmt.shape.indent.to_string(fmt.config);
 
     // Strip line breaks.
     // With this regex applied, all remaining whitespaces are significant
@@ -88,26 +100,55 @@ pub fn rewrite_string<'a>(orig: &str, fmt: &StringFormat<'a>) -> Option<String>
     // Snip a line at a time from `stripped_str` until it is used up. Push the snippet
     // onto result.
     let mut cur_max_chars = max_chars_with_indent;
+    let is_bareline_ok = fmt.line_start.is_empty() || is_whitespace(fmt.line_start);
     loop {
         // All the input starting at cur_start fits on the current line
         if graphemes.len() - cur_start <= cur_max_chars {
-            result.push_str(&graphemes[cur_start..].join(""));
+            for (i, grapheme) in graphemes[cur_start..].iter().enumerate() {
+                if is_line_feed(grapheme) {
+                    // take care of blank lines
+                    result = trim_right_but_line_feed(fmt.trim_end, result);
+                    result.push_str("\n");
+                    if !is_bareline_ok && cur_start + i + 1 < graphemes.len() {
+                        result.push_str(&indent_without_newline);
+                        result.push_str(fmt.line_start);
+                    }
+                } else {
+                    result.push_str(grapheme);
+                }
+            }
+            result = trim_right_but_line_feed(fmt.trim_end, result);
             break;
         }
 
         // The input starting at cur_start needs to be broken
-        match break_string(cur_max_chars, fmt.trim_end, &graphemes[cur_start..]) {
+        match break_string(
+            cur_max_chars,
+            fmt.trim_end,
+            fmt.line_end,
+            &graphemes[cur_start..],
+        ) {
             SnippetState::LineEnd(line, len) => {
                 result.push_str(&line);
                 result.push_str(fmt.line_end);
-                result.push_str(&indent);
+                result.push_str(&indent_with_newline);
                 result.push_str(fmt.line_start);
-                cur_max_chars = max_chars_with_indent;
+                cur_max_chars = newline_max_chars;
                 cur_start += len;
             }
-            SnippetState::Overflow(line, len) => {
+            SnippetState::EndWithLineFeed(line, len) => {
+                if line == "\n" && fmt.trim_end {
+                    result = result.trim_right().to_string();
+                }
                 result.push_str(&line);
-                cur_max_chars = max_chars_without_indent;
+                if is_bareline_ok {
+                    // the next line can benefit from the full width
+                    cur_max_chars = max_chars_without_indent;
+                } else {
+                    result.push_str(&indent_without_newline);
+                    result.push_str(fmt.line_start);
+                    cur_max_chars = max_chars_with_indent;
+                }
                 cur_start += len;
             }
             SnippetState::EndOfInput(line) => {
@@ -121,6 +162,43 @@ pub fn rewrite_string<'a>(orig: &str, fmt: &StringFormat<'a>) -> Option<String>
     wrap_str(result, fmt.config.max_width(), fmt.shape)
 }
 
+/// Returns the index to the end of the url if the given string includes an
+/// URL or alike. Otherwise, returns None;
+fn detect_url(s: &[&str], index: usize) -> Option<usize> {
+    let start = match s[..=index].iter().rposition(|g| is_whitespace(g)) {
+        Some(pos) => pos + 1,
+        None => 0,
+    };
+    if s.len() < start + 8 {
+        return None;
+    }
+    let prefix = s[start..start + 8].concat();
+    if prefix.starts_with("https://")
+        || prefix.starts_with("http://")
+        || prefix.starts_with("ftp://")
+        || prefix.starts_with("file://")
+    {
+        match s[index..].iter().position(|g| is_whitespace(g)) {
+            Some(pos) => Some(index + pos - 1),
+            None => Some(s.len() - 1),
+        }
+    } else {
+        None
+    }
+}
+
+/// Trims whitespaces to the right except for the line feed character.
+fn trim_right_but_line_feed(trim_end: bool, result: String) -> String {
+    let whitespace_except_line_feed = |c: char| c.is_whitespace() && c != '\n';
+    if trim_end && result.ends_with(whitespace_except_line_feed) {
+        result
+            .trim_right_matches(whitespace_except_line_feed)
+            .to_string()
+    } else {
+        result
+    }
+}
+
 /// Result of breaking a string so it fits in a line and the state it ended in.
 /// The state informs about what to do with the snippet and how to continue the breaking process.
 #[derive(Debug, PartialEq)]
@@ -129,55 +207,95 @@ enum SnippetState {
     EndOfInput(String),
     /// The input could be broken and the returned snippet should be ended with a
     /// `[StringFormat::line_end]`. The next snippet needs to be indented.
+    ///
+    /// The returned string is the line to print out and the number is the length that got read in
+    /// the text being rewritten. That length may be greater than the returned string if trailing
+    /// whitespaces got trimmed.
     LineEnd(String, usize),
-    /// The input could be broken but the returned snippet should not be ended with a
-    /// `[StringFormat::line_end]` because the whitespace is significant. Therefore, the next
-    /// snippet should not be indented.
-    Overflow(String, usize),
+    /// The input could be broken but a newline is present that cannot be trimmed. The next snippet
+    /// to be rewritten *could* use more width than what is specified by the given shape. For
+    /// example with a multiline string, the next snippet does not need to be indented, allowing
+    /// more characters to be fit within a line.
+    ///
+    /// The returned string is the line to print out and the number is the length that got read in
+    /// the text being rewritten.
+    EndWithLineFeed(String, usize),
+}
+
+fn not_whitespace_except_line_feed(g: &str) -> bool {
+    is_line_feed(g) || !is_whitespace(g)
 }
 
 /// Break the input string at a boundary character around the offset `max_chars`. A boundary
 /// character is either a punctuation or a whitespace.
-fn break_string(max_chars: usize, trim_end: bool, input: &[&str]) -> SnippetState {
+fn break_string(max_chars: usize, trim_end: bool, line_end: &str, input: &[&str]) -> SnippetState {
     let break_at = |index /* grapheme at index is included */| {
-        // Take in any whitespaces to the left/right of `input[index]` and
-        // check if there is a line feed, in which case whitespaces needs to be kept.
-        let mut index_minus_ws = index;
-        for (i, grapheme) in input[0..=index].iter().enumerate().rev() {
-            if !trim_end && is_line_feed(grapheme) {
-                return SnippetState::Overflow(input[0..=i].join("").to_string(), i + 1);
-            } else if !is_whitespace(grapheme) {
-                index_minus_ws = i;
+        // Take in any whitespaces to the left/right of `input[index]` while
+        // preserving line feeds
+        let index_minus_ws = input[0..=index]
+            .iter()
+            .rposition(|grapheme| not_whitespace_except_line_feed(grapheme))
+            .unwrap_or(index);
+        // Take into account newlines occuring in input[0..=index], i.e., the possible next new
+        // line. If there is one, then text after it could be rewritten in a way that the available
+        // space is fully used.
+        for (i, grapheme) in input[0..=index].iter().enumerate() {
+            if is_line_feed(grapheme) {
+                if i <= index_minus_ws {
+                    let mut line = &input[0..i].concat()[..];
+                    if trim_end {
+                        line = line.trim_right();
+                    }
+                    return SnippetState::EndWithLineFeed(format!("{}\n", line), i + 1);
+                }
                 break;
             }
         }
+
         let mut index_plus_ws = index;
         for (i, grapheme) in input[index + 1..].iter().enumerate() {
             if !trim_end && is_line_feed(grapheme) {
-                return SnippetState::Overflow(
-                    input[0..=index + 1 + i].join("").to_string(),
+                return SnippetState::EndWithLineFeed(
+                    input[0..=index + 1 + i].concat(),
                     index + 2 + i,
                 );
-            } else if !is_whitespace(grapheme) {
+            } else if not_whitespace_except_line_feed(grapheme) {
                 index_plus_ws = index + i;
                 break;
             }
         }
 
         if trim_end {
-            SnippetState::LineEnd(
-                input[0..=index_minus_ws].join("").to_string(),
-                index_plus_ws + 1,
-            )
+            SnippetState::LineEnd(input[0..=index_minus_ws].concat(), index_plus_ws + 1)
         } else {
-            SnippetState::LineEnd(
-                input[0..=index_plus_ws].join("").to_string(),
-                index_plus_ws + 1,
-            )
+            SnippetState::LineEnd(input[0..=index_plus_ws].concat(), index_plus_ws + 1)
         }
     };
 
     // Find the position in input for breaking the string
+    if line_end.is_empty()
+        && trim_end
+        && !is_whitespace(input[max_chars - 1])
+        && is_whitespace(input[max_chars])
+    {
+        // At a breaking point already
+        // The line won't invalidate the rewriting because:
+        // - no extra space needed for the line_end character
+        // - extra whitespaces to the right can be trimmed
+        return break_at(max_chars - 1);
+    }
+    if let Some(url_index_end) = detect_url(input, max_chars) {
+        let index_plus_ws = url_index_end + input[url_index_end..]
+            .iter()
+            .skip(1)
+            .position(|grapheme| not_whitespace_except_line_feed(grapheme))
+            .unwrap_or(0);
+        return if trim_end {
+            SnippetState::LineEnd(input[..=url_index_end].concat(), index_plus_ws + 1)
+        } else {
+            return SnippetState::LineEnd(input[..=index_plus_ws].concat(), index_plus_ws + 1);
+        };
+    }
     match input[0..max_chars]
         .iter()
         .rposition(|grapheme| is_whitespace(grapheme))
@@ -200,7 +318,7 @@ fn break_string(max_chars: usize, trim_end: bool, input: &[&str]) -> SnippetStat
                 // A boundary was found after the line limit
                 Some(index) => break_at(max_chars + index),
                 // No boundary to the right, the input cannot be broken
-                None => SnippetState::EndOfInput(input.join("").to_string()),
+                None => SnippetState::EndOfInput(input.concat()),
             },
         },
     }
@@ -223,7 +341,8 @@ fn is_punctuation(grapheme: &str) -> bool {
 
 #[cfg(test)]
 mod test {
-    use super::{break_string, rewrite_string, SnippetState, StringFormat};
+    use super::{break_string, detect_url, rewrite_string, SnippetState, StringFormat};
+    use config::Config;
     use shape::{Indent, Shape};
     use unicode_segmentation::UnicodeSegmentation;
 
@@ -231,7 +350,7 @@ mod test {
     fn issue343() {
         let config = Default::default();
         let fmt = StringFormat::new(Shape::legacy(2, Indent::empty()), &config);
-        rewrite_string("eq_", &fmt);
+        rewrite_string("eq_", &fmt, 2);
     }
 
     #[test]
@@ -239,11 +358,11 @@ fn should_break_on_whitespace() {
         let string = "Placerat felis. Mauris porta ante sagittis purus.";
         let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
         assert_eq!(
-            break_string(20, false, &graphemes[..]),
+            break_string(20, false, "", &graphemes[..]),
             SnippetState::LineEnd("Placerat felis. ".to_string(), 16)
         );
         assert_eq!(
-            break_string(20, true, &graphemes[..]),
+            break_string(20, true, "", &graphemes[..]),
             SnippetState::LineEnd("Placerat felis.".to_string(), 16)
         );
     }
@@ -253,7 +372,7 @@ fn should_break_on_punctuation() {
         let string = "Placerat_felis._Mauris_porta_ante_sagittis_purus.";
         let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
         assert_eq!(
-            break_string(20, false, &graphemes[..]),
+            break_string(20, false, "", &graphemes[..]),
             SnippetState::LineEnd("Placerat_felis.".to_string(), 15)
         );
     }
@@ -263,11 +382,11 @@ fn should_break_forward() {
         let string = "Venenatis_tellus_vel_tellus. Aliquam aliquam dolor at justo.";
         let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
         assert_eq!(
-            break_string(20, false, &graphemes[..]),
+            break_string(20, false, "", &graphemes[..]),
             SnippetState::LineEnd("Venenatis_tellus_vel_tellus. ".to_string(), 29)
         );
         assert_eq!(
-            break_string(20, true, &graphemes[..]),
+            break_string(20, true, "", &graphemes[..]),
             SnippetState::LineEnd("Venenatis_tellus_vel_tellus.".to_string(), 29)
         );
     }
@@ -277,7 +396,7 @@ fn nothing_to_break() {
         let string = "Venenatis_tellus_vel_tellus";
         let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
         assert_eq!(
-            break_string(20, false, &graphemes[..]),
+            break_string(20, false, "", &graphemes[..]),
             SnippetState::EndOfInput("Venenatis_tellus_vel_tellus".to_string())
         );
     }
@@ -287,21 +406,21 @@ fn significant_whitespaces() {
         let string = "Neque in sem.      \n      Pellentesque tellus augue.";
         let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
         assert_eq!(
-            break_string(15, false, &graphemes[..]),
-            SnippetState::Overflow("Neque in sem.      \n".to_string(), 20)
+            break_string(15, false, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Neque in sem.      \n".to_string(), 20)
         );
         assert_eq!(
-            break_string(25, false, &graphemes[..]),
-            SnippetState::Overflow("Neque in sem.      \n".to_string(), 20)
+            break_string(25, false, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Neque in sem.      \n".to_string(), 20)
         );
-        // if `StringFormat::line_end` is true, then the line feed does not matter anymore
+
         assert_eq!(
-            break_string(15, true, &graphemes[..]),
-            SnippetState::LineEnd("Neque in sem.".to_string(), 26)
+            break_string(15, true, "", &graphemes[..]),
+            SnippetState::LineEnd("Neque in sem.".to_string(), 19)
         );
         assert_eq!(
-            break_string(25, true, &graphemes[..]),
-            SnippetState::LineEnd("Neque in sem.".to_string(), 26)
+            break_string(25, true, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Neque in sem.\n".to_string(), 20)
         );
     }
 
@@ -310,12 +429,250 @@ fn big_whitespace() {
         let string = "Neque in sem.            Pellentesque tellus augue.";
         let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
         assert_eq!(
-            break_string(20, false, &graphemes[..]),
+            break_string(20, false, "", &graphemes[..]),
             SnippetState::LineEnd("Neque in sem.            ".to_string(), 25)
         );
         assert_eq!(
-            break_string(20, true, &graphemes[..]),
+            break_string(20, true, "", &graphemes[..]),
             SnippetState::LineEnd("Neque in sem.".to_string(), 25)
         );
     }
+
+    #[test]
+    fn newline_in_candidate_line() {
+        let string = "Nulla\nconsequat erat at massa. Vivamus id mi.";
+
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(25, false, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Nulla\n".to_string(), 6)
+        );
+        assert_eq!(
+            break_string(25, true, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Nulla\n".to_string(), 6)
+        );
+
+        let mut config: Config = Default::default();
+        config.set().max_width(27);
+        let fmt = StringFormat::new(Shape::legacy(25, Indent::empty()), &config);
+        let rewritten_string = rewrite_string(string, &fmt, 27);
+        assert_eq!(
+            rewritten_string,
+            Some("\"Nulla\nconsequat erat at massa. \\\n Vivamus id mi.\"".to_string())
+        );
+    }
+
+    #[test]
+    fn last_line_fit_with_trailing_whitespaces() {
+        let string = "Vivamus id mi.  ";
+        let config: Config = Default::default();
+        let mut fmt = StringFormat::new(Shape::legacy(25, Indent::empty()), &config);
+
+        fmt.trim_end = true;
+        let rewritten_string = rewrite_string(string, &fmt, 25);
+        assert_eq!(rewritten_string, Some("\"Vivamus id mi.\"".to_string()));
+
+        fmt.trim_end = false; // default value of trim_end
+        let rewritten_string = rewrite_string(string, &fmt, 25);
+        assert_eq!(rewritten_string, Some("\"Vivamus id mi.  \"".to_string()));
+    }
+
+    #[test]
+    fn last_line_fit_with_newline() {
+        let string = "Vivamus id mi.\nVivamus id mi.";
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(100, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let rewritten_string = rewrite_string(string, &fmt, 100);
+        assert_eq!(
+            rewritten_string,
+            Some("Vivamus id mi.\n    // Vivamus id mi.".to_string())
+        );
+    }
+
+    #[test]
+    fn overflow_in_non_string_content() {
+        let comment = "Aenean metus.\nVestibulum ac lacus. Vivamus porttitor";
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(30, Indent::from_width(&config, 8)),
+            trim_end: true,
+            config: &config,
+        };
+
+        assert_eq!(
+            rewrite_string(comment, &fmt, 30),
+            Some(
+                "Aenean metus.\n        // Vestibulum ac lacus. Vivamus\n        // porttitor"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn overflow_in_non_string_content_with_line_end() {
+        let comment = "Aenean metus.\nVestibulum ac lacus. Vivamus porttitor";
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "@",
+            shape: Shape::legacy(30, Indent::from_width(&config, 8)),
+            trim_end: true,
+            config: &config,
+        };
+
+        assert_eq!(
+            rewrite_string(comment, &fmt, 30),
+            Some(
+                "Aenean metus.\n        // Vestibulum ac lacus. Vivamus@\n        // porttitor"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn blank_line_with_non_empty_line_start() {
+        let config: Config = Default::default();
+        let mut fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(30, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let comment = "Aenean metus. Vestibulum\n\nac lacus. Vivamus porttitor";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 30),
+            Some(
+                "Aenean metus. Vestibulum\n    //\n    // ac lacus. Vivamus porttitor".to_string()
+            )
+        );
+
+        fmt.shape = Shape::legacy(15, Indent::from_width(&config, 4));
+        let comment = "Aenean\n\nmetus. Vestibulum ac lacus. Vivamus porttitor";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 15),
+            Some(
+                r#"Aenean
+    //
+    // metus. Vestibulum
+    // ac lacus. Vivamus
+    // porttitor"#
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn retain_blank_lines() {
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(20, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let comment = "Aenean\n\nmetus. Vestibulum ac lacus.\n\n";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 20),
+            Some(
+                "Aenean\n    //\n    // metus. Vestibulum ac\n    // lacus.\n    //\n".to_string()
+            )
+        );
+
+        let comment = "Aenean\n\nmetus. Vestibulum ac lacus.\n";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 20),
+            Some("Aenean\n    //\n    // metus. Vestibulum ac\n    // lacus.\n".to_string())
+        );
+
+        let comment = "Aenean\n        \nmetus. Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 20),
+            Some("Aenean\n    //\n    // metus. Vestibulum ac\n    // lacus.".to_string())
+        );
+    }
+
+    #[test]
+    fn boundary_on_edge() {
+        let config: Config = Default::default();
+        let mut fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(13, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let comment = "Aenean metus. Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 13),
+            Some("Aenean metus.\n    // Vestibulum ac\n    // lacus.".to_string())
+        );
+
+        fmt.trim_end = false;
+        let comment = "Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 13),
+            Some("Vestibulum \n    // ac lacus.".to_string())
+        );
+
+        fmt.trim_end = true;
+        fmt.line_end = "\\";
+        let comment = "Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 13),
+            Some("Vestibulum\\\n    // ac lacus.".to_string())
+        );
+    }
+
+    #[test]
+    fn detect_urls() {
+        let string = "aaa http://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(21));
+
+        let string = "https://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 0), Some(18));
+
+        let string = "aaa ftp://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(20));
+
+        let string = "aaa file://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(21));
+
+        let string = "aaa http not an url";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 6), None);
+
+        let string = "aaa file://example.org";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(21));
+    }
 }