add configuration to multipart::Form to choose percent-encoding format

Sets the default back to `path-segment`, since the "fix" breaks anyone
using reqwest from before.

Closes #363

src/multipart.rs

@@ -6,8 +6,7 @@ use std::io::{self, Cursor, Read};
 use std::path::Path;
 
 use mime_guess::{self, Mime};
-use url::percent_encoding;
-use url::percent_encoding::EncodeSet;
+use url::percent_encoding::{self, EncodeSet, PATH_SEGMENT_ENCODE_SET};
 use uuid::Uuid;
 use http::HeaderMap;
 
@@ -18,6 +17,12 @@ pub struct Form {
     boundary: String,
     fields: Vec<(Cow<'static, str>, Part)>,
     headers: Vec<Vec<u8>>,
+    percent_encoding: PercentEncoding,
+}
+
+enum PercentEncoding {
+    PathSegment,
+    AttrChar,
 }
 
 impl Form {
@@ -27,6 +32,7 @@ impl Form {
             boundary: format!("{}", Uuid::new_v4().to_simple()),
             fields: Vec::new(),
             headers: Vec::new(),
+            percent_encoding: PercentEncoding::PathSegment,
         }
     }
 
@@ -84,6 +90,18 @@ impl Form {
         self
     }
 
+    /// Configure this `Form` to percent-encode using the `path-segment` rules.
+    pub fn percent_encode_path_segment(mut self) -> Form {
+        self.percent_encoding = PercentEncoding::PathSegment;
+        self
+    }
+
+    /// Configure this `Form` to percent-encode using the `attr-char` rules.
+    pub fn percent_encode_attr_chars(mut self) -> Form {
+        self.percent_encoding = PercentEncoding::AttrChar;
+        self
+    }
+
     pub(crate) fn reader(self) -> Reader {
         Reader::new(self)
     }
@@ -98,7 +116,7 @@ impl Form {
                 Some(value_length) => {
                     // We are constructing the header just to get its length. To not have to
                     // construct it again when the request is sent we cache these headers.
-                    let header = header(name, field);
+                    let header = self.percent_encoding.encode_headers(name, field);
                     let header_length = header.len();
                     self.headers.push(header);
                     // The additions mimick the format string out of which the field is constructed
@@ -277,7 +295,7 @@ impl Reader {
                 let mut h = if self.form.headers.len() > 0 {
                     self.form.headers.remove(0)
                 } else {
-                    header(&name, &field)
+                    self.form.percent_encoding.encode_headers(&name, &field)
                 };
                 h.extend_from_slice(b"\r\n\r\n");
                 h
@@ -350,12 +368,13 @@ impl EncodeSet for AttrCharEncodeSet {
 
 }
 
-fn header(name: &str, field: &Part) -> Vec<u8> {
+impl PercentEncoding {
+    fn encode_headers(&self, name: &str, field: &Part) -> Vec<u8> {
         let s = format!(
             "Content-Disposition: form-data; {}{}{}",
-        format_parameter("name", name),
+            self.format_parameter("name", name),
             match field.file_name {
-            Some(ref file_name) => format!("; {}", format_parameter("filename", file_name)),
+                Some(ref file_name) => format!("; {}", self.format_parameter("filename", file_name)),
                 None => String::new(),
             },
             match field.mime {
@@ -372,10 +391,17 @@ fn header(name: &str, field: &Part) -> Vec<u8> {
         })
     }
 
-fn format_parameter(name: &str, value: &str) -> String {
-    let legal_value =
+    fn format_parameter(&self, name: &str, value: &str) -> String {
+        let legal_value = match *self {
+            PercentEncoding::PathSegment => {
+                percent_encoding::utf8_percent_encode(value, PATH_SEGMENT_ENCODE_SET)
+                    .to_string()
+            },
+            PercentEncoding::AttrChar => {
                 percent_encoding::utf8_percent_encode(value, AttrCharEncodeSet)
-            .to_string();
+                    .to_string()
+            },
+        };
         if value.len() == legal_value.len() {
             // nothing has been percent encoded
             format!("{}=\"{}\"", name, value)
@@ -384,6 +410,8 @@ fn format_parameter(name: &str, value: &str) -> String {
             format!("{}*=utf-8''{}", name, legal_value)
         }
     }
+}
+
 
 #[cfg(test)]
 mod tests {
@@ -507,8 +535,15 @@ mod tests {
     fn header_percent_encoding() {
         let name = "start%'\"\r\nßend";
         let field = Part::text("");
-        let expected = "Content-Disposition: form-data; name*=utf-8''start%25%27%22%0D%0A%C3%9Fend";
 
-        assert_eq!(header(name, &field), expected.as_bytes());
+        assert_eq!(
+            PercentEncoding::PathSegment.encode_headers(name, &field),
+            &b"Content-Disposition: form-data; name*=utf-8''start%25'%22%0D%0A%C3%9Fend"[..]
+        );
+
+        assert_eq!(
+            PercentEncoding::AttrChar.encode_headers(name, &field),
+            &b"Content-Disposition: form-data; name*=utf-8''start%25%27%22%0D%0A%C3%9Fend"[..]
+        );
     }
 }