Fix usage of split_inclusive in event parser (#31)

* Use cimg/rust 1.59

* Fix usage of split_inclusive in event parser logic

It was relying on old behavior where Some(empty slice) would be returned
if there were no matches. This was updated in more recent rust versions to return None,
but CircleCI was using a much older version of rust than I have locally.

* Add a property-test to exercise event parsing logic

Author: cwaldren-ld

.circleci/config.yml

@@ -2,18 +2,14 @@ version: 2
 jobs:
   build:
     docker:
-      - image: circleci/rust:latest
-
+      - image: cimg/rust:1.59.0
     steps:
       - checkout
-
       - run:
-          name: Install clippy
-          command: rustup component add clippy
-      - run:
-          name: Install rustfmt
-          command: rustup component add rustfmt
-
+          name: Check Version
+          command: |
+            cargo --version
+            rustc --version
       - run:
           name: Check consistent formatting
           command: cargo fmt && git diff --exit-code

eventsource-client/Cargo.toml

@@ -27,6 +27,8 @@ maplit = "1.0.1"
 simplelog = "0.5.3"
 tokio = { version = "1.2.0", features = ["macros", "rt-multi-thread"] }
 test-case = "1.2.3"
+proptest = "1.0.0"
+
 
 [features]
 default = ["rustls"]

eventsource-client/src/event_parser.rs

@@ -281,42 +281,39 @@ impl EventParser {
     // incomplete lines from previous chunks.
     fn decode_and_buffer_lines(&mut self, chunk: Bytes) {
         let mut lines = chunk.split_inclusive(|&b| b == b'\n' || b == b'\r');
-
         // The first and last elements in this split are special. The spec requires lines to be
         // terminated. But lines may span chunks, so:
         //  * the last line, if non-empty (i.e. if chunk didn't end with a line terminator),
         //    should be buffered as an incomplete line
         //  * the first line should be appended to the incomplete line, if any
 
         if let Some(incomplete_line) = self.incomplete_line.as_mut() {
-            let line = lines
-                .next()
-                // split always returns at least one item
-                .unwrap();
-            trace!(
-                "extending line from previous chunk: {:?}+{:?}",
-                logify(incomplete_line),
-                logify(line)
-            );
+            if let Some(line) = lines.next() {
+                trace!(
+                    "extending line from previous chunk: {:?}+{:?}",
+                    logify(incomplete_line),
+                    logify(line)
+                );
 
-            self.last_char_was_cr = false;
-            if !line.is_empty() {
-                // Checking the last character handles lines where the last character is a
-                // terminator, but also where the entire line is a terminator.
-                match line.last().unwrap() {
-                    b'\r' => {
-                        incomplete_line.extend_from_slice(&line[..line.len() - 1]);
-                        let il = self.incomplete_line.take();
-                        self.complete_lines.push_back(il.unwrap());
-                        self.last_char_was_cr = true;
-                    }
-                    b'\n' => {
-                        incomplete_line.extend_from_slice(&line[..line.len() - 1]);
-                        let il = self.incomplete_line.take();
-                        self.complete_lines.push_back(il.unwrap());
-                    }
-                    _ => incomplete_line.extend_from_slice(line),
-                };
+                self.last_char_was_cr = false;
+                if !line.is_empty() {
+                    // Checking the last character handles lines where the last character is a
+                    // terminator, but also where the entire line is a terminator.
+                    match line.last().unwrap() {
+                        b'\r' => {
+                            incomplete_line.extend_from_slice(&line[..line.len() - 1]);
+                            let il = self.incomplete_line.take();
+                            self.complete_lines.push_back(il.unwrap());
+                            self.last_char_was_cr = true;
+                        }
+                        b'\n' => {
+                            incomplete_line.extend_from_slice(&line[..line.len() - 1]);
+                            let il = self.incomplete_line.take();
+                            self.complete_lines.push_back(il.unwrap());
+                        }
+                        _ => incomplete_line.extend_from_slice(line),
+                    };
+                }
             }
         }
 
@@ -375,6 +372,7 @@ impl EventParser {
 #[cfg(test)]
 mod tests {
     use super::{Error::*, *};
+    use proptest::proptest;
     use test_case::test_case;
 
     fn field<'a>(key: &'a str, value: &'a str) -> Result<Option<(&'a str, &'a str)>> {
@@ -671,4 +669,13 @@ mod tests {
         std::fs::read(format!("test-data/{}", name))
             .unwrap_or_else(|_| panic!("couldn't read {}", name))
     }
+
+    proptest! {
+        #[test]
+        fn test_decode_and_buffer_lines_does_not_crash(next in "(\r\n|\r|\n)*event: [^\n\r:]*(\r\n|\r|\n)", previous in "(\r\n|\r|\n)*event: [^\n\r:]*(\r\n|\r|\n)") {
+            let mut parser = EventParser::new();
+            parser.incomplete_line = Some(previous.as_bytes().to_vec());
+            parser.decode_and_buffer_lines(Bytes::from(next));
+        }
+    }
 }