Add file function to async::multipart (#2106)

* Add file function to async_impl::multipart

* Add test for asynchronous file function in multipart

* Fix doc of file function in blocking::multipart

* Fix test

Follow up on this pull request
#2059

* Fix doc test

src/async_impl/multipart.rs

@@ -3,9 +3,16 @@ use std::borrow::Cow;
 use std::fmt;
 use std::pin::Pin;
 
+#[cfg(feature = "stream")]
+use std::io;
+#[cfg(feature = "stream")]
+use std::path::Path;
+
 use bytes::Bytes;
 use mime_guess::Mime;
 use percent_encoding::{self, AsciiSet, NON_ALPHANUMERIC};
+#[cfg(feature = "stream")]
+use tokio::fs::File;
 
 use futures_core::Stream;
 use futures_util::{future, stream, StreamExt};
@@ -82,6 +89,33 @@ impl Form {
         self.part(name, Part::text(value))
     }
 
+    /// Adds a file field.
+    ///
+    /// The path will be used to try to guess the filename and mime.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # async fn run() -> std::io::Result<()> {
+    /// let form = reqwest::multipart::Form::new()
+    ///     .file("key", "/path/to/file").await?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// # Errors
+    ///
+    /// Errors when the file cannot be opened.
+    #[cfg(feature = "stream")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "stream")))]
+    pub async fn file<T, U>(self, name: T, path: U) -> io::Result<Form>
+    where
+        T: Into<Cow<'static, str>>,
+        U: AsRef<Path>,
+    {
+        Ok(self.part(name, Part::file(path).await?))
+    }
+
     /// Adds a customized Part.
     pub fn part<T>(self, name: T, part: Part) -> Form
     where
@@ -218,6 +252,30 @@ impl Part {
         Part::new(value.into(), Some(length))
     }
 
+    /// Makes a file parameter.
+    ///
+    /// # Errors
+    ///
+    /// Errors when the file cannot be opened.
+    #[cfg(feature = "stream")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "stream")))]
+    pub async fn file<T: AsRef<Path>>(path: T) -> io::Result<Part> {
+        let path = path.as_ref();
+        let file_name = path
+            .file_name()
+            .map(|filename| filename.to_string_lossy().into_owned());
+        let ext = path.extension().and_then(|ext| ext.to_str()).unwrap_or("");
+        let mime = mime_guess::from_ext(ext).first_or_octet_stream();
+        let file = File::open(path).await?;
+        let field = Part::stream(file).mime(mime);
+
+        Ok(if let Some(file_name) = file_name {
+            field.file_name(file_name)
+        } else {
+            field
+        })
+    }
+
     fn new(value: Body, body_length: Option<u64>) -> Part {
         Part {
             meta: PartMetadata::new(),

src/blocking/multipart.rs

@@ -104,7 +104,7 @@ impl Form {
     ///
     /// ```no_run
     /// # fn run() -> std::io::Result<()> {
-    /// let files = reqwest::blocking::multipart::Form::new()
+    /// let form = reqwest::blocking::multipart::Form::new()
     ///     .file("key", "/path/to/file")?;
     /// # Ok(())
     /// # }

tests/multipart.rs

@@ -175,3 +175,58 @@ fn blocking_file_part() {
     assert_eq!(res.url().as_str(), &url);
     assert_eq!(res.status(), reqwest::StatusCode::OK);
 }
+
+#[cfg(feature = "stream")]
+#[tokio::test]
+async fn async_impl_file_part() {
+    let _ = env_logger::try_init();
+
+    let form = reqwest::multipart::Form::new()
+        .file("foo", "Cargo.lock")
+        .await
+        .unwrap();
+
+    let fcontents = std::fs::read_to_string("Cargo.lock").unwrap();
+
+    let expected_body = format!(
+        "\
+         --{0}\r\n\
+         Content-Disposition: form-data; name=\"foo\"; filename=\"Cargo.lock\"\r\n\
+         Content-Type: application/octet-stream\r\n\r\n\
+         {1}\r\n\
+         --{0}--\r\n\
+         ",
+        form.boundary(),
+        fcontents
+    );
+
+    let ct = format!("multipart/form-data; boundary={}", form.boundary());
+
+    let server = server::http(move |req| {
+        let ct = ct.clone();
+        let expected_body = expected_body.clone();
+        async move {
+            assert_eq!(req.method(), "POST");
+            assert_eq!(req.headers()["content-type"], ct);
+            assert_eq!(req.headers()["transfer-encoding"], "chunked");
+
+            let full = req.collect().await.unwrap().to_bytes();
+
+            assert_eq!(full, expected_body.as_bytes());
+
+            http::Response::default()
+        }
+    });
+
+    let url = format!("http://{}/multipart/3", server.addr());
+
+    let res = reqwest::Client::new()
+        .post(&url)
+        .multipart(form)
+        .send()
+        .await
+        .unwrap();
+
+    assert_eq!(res.url().as_str(), &url);
+    assert_eq!(res.status(), reqwest::StatusCode::OK);
+}