1 files changed, 103 insertions, 0 deletions
diff --git a/structopt/structopt-derive/src/doc_comments.rs b/structopt/structopt-derive/src/doc_comments.rs
new file mode 100644
index 0000000..06e1b14
--- /dev/null
+++ b/structopt/structopt-derive/src/doc_comments.rs
@@ -0,0 +1,103 @@
+//! The preprocessing we apply to doc comments.
+//!
+//! structopt works in terms of "paragraphs". Paragraph is a sequence of
+//! non-empty adjacent lines, delimited by sequences of blank (whitespace only) lines.
+
+use crate::attrs::Method;
+use quote::{format_ident, quote};
+use std::iter;
+
+pub fn process_doc_comment(lines: Vec<String>, name: &str, preprocess: bool) -> Vec<Method> {
+    // multiline comments (`/** ... */`) may have LFs (`\n`) in them,
+    // we need to split so we could handle the lines correctly
+    //
+    // we also need to remove leading and trailing blank lines
+    let mut lines: Vec<&str> = lines
+        .iter()
+        .skip_while(|s| is_blank(s))
+        .flat_map(|s| s.split('\n'))
+        .collect();
+
+    while let Some(true) = lines.last().map(|s| is_blank(s)) {
+        lines.pop();
+    }
+
+    // remove one leading space no matter what
+    for line in lines.iter_mut() {
+        if line.starts_with(' ') {
+            *line = &line[1..];
+        }
+    }
+
+    if lines.is_empty() {
+        return vec![];
+    }
+
+    let short_name = format_ident!("{}", name);
+    let long_name = format_ident!("long_{}", name);
+
+    if let Some(first_blank) = lines.iter().position(|s| is_blank(s)) {
+        let (short, long) = if preprocess {
+            let paragraphs = split_paragraphs(&lines);
+            let short = paragraphs[0].clone();
+            let long = paragraphs.join("\n\n");
+            (remove_period(short), long)
+        } else {
+            let short = lines[..first_blank].join("\n");
+            let long = lines.join("\n");
+            (short, long)
+        };
+
+        vec![
+            Method::new(short_name, quote!(#short)),
+            Method::new(long_name, quote!(#long)),
+        ]
+    } else {
+        let short = if preprocess {
+            let s = merge_lines(&lines);
+            remove_period(s)
+        } else {
+            lines.join("\n")
+        };
+
+        vec![Method::new(short_name, quote!(#short))]
+    }
+}
+
+fn split_paragraphs(lines: &[&str]) -> Vec<String> {
+    let mut last_line = 0;
+    iter::from_fn(|| {
+        let slice = &lines[last_line..];
+        let start = slice.iter().position(|s| !is_blank(s)).unwrap_or(0);
+
+        let slice = &slice[start..];
+        let len = slice
+            .iter()
+            .position(|s| is_blank(s))
+            .unwrap_or(slice.len());
+
+        last_line += start + len;
+
+        if len != 0 {
+            Some(merge_lines(&slice[..len]))
+        } else {
+            None
+        }
+    })
+    .collect()
+}
+
+fn remove_period(mut s: String) -> String {
+    if s.ends_with('.') && !s.ends_with("..") {
+        s.pop();
+    }
+    s
+}
+
+fn is_blank(s: &str) -> bool {
+    s.trim().is_empty()
+}
+
+fn merge_lines(lines: &[&str]) -> String {
+    lines.iter().map(|s| s.trim()).collect::<Vec<_>>().join(" ")
+}