Add support for UTF-8 BOM encoding (#28)

The UTF-8 Byte Order Mark `\ufeff` will be ignored when parsing.

See #27

dotenv/src/iter.rs

@@ -22,7 +22,9 @@ impl<R: Read> Iter<R> {
     }
 
     /// Loads all variables found in the `reader` into the environment.
-    pub fn load(self) -> Result<()> {
+    pub fn load(mut self) -> Result<()> {
+        self.remove_bom()?;
+
         for item in self {
             let (key, value) = item?;
             if env::var(&key).is_err() {
@@ -32,6 +34,16 @@ impl<R: Read> Iter<R> {
 
         Ok(())
     }
+
+    fn remove_bom(&mut self) -> Result<()> {
+        let buffer = self.lines.buf.fill_buf().map_err(Error::Io)?;
+        // https://www.compart.com/en/unicode/U+FEFF
+        if buffer.starts_with(&[0xEF, 0xBB, 0xBF]) {
+            // remove the BOM from the bufreader
+            self.lines.buf.consume(3);
+        }
+        Ok(())
+    }
 }
 
 struct QuotedLines<B> {

dotenv/tests/test-ignore-bom.rs

@@ -0,0 +1,22 @@
+mod common;
+
+use crate::common::*;
+use dotenvy::*;
+use std::{env, error::Error, result::Result};
+
+#[test]
+fn test_ignore_bom() -> Result<(), Box<dyn Error>> {
+    let bom = "\u{feff}";
+    let dir = tempdir_with_dotenv(&format!("{}TESTKEY=test_val", bom))?;
+
+    let mut path = env::current_dir()?;
+    path.push(".env");
+
+    from_path(&path)?;
+
+    assert_eq!(env::var("TESTKEY")?, "test_val");
+
+    env::set_current_dir(dir.path().parent().unwrap())?;
+    dir.close()?;
+    Ok(())
+}