fix: strip bom (#14)

src/format_text.rs

@@ -8,16 +8,24 @@ use crate::configuration::Configuration;
 use crate::generation::generate;
 
 pub fn format_text(_file_path: &Path, text: &str, config: &Configuration) -> Result<Option<String>> {
-  let node = parse_node(text)?;
-
-  let result = dprint_core::formatting::format(|| generate(&node, text, config), config_to_print_options(text, config));
+  let result = format_inner(text, config)?;
   if result == text {
     Ok(None)
   } else {
     Ok(Some(result))
   }
 }
 
+fn format_inner(text: &str, config: &Configuration) -> Result<String> {
+  let text = strip_bom(text);
+  let node = parse_node(text)?;
+
+  Ok(dprint_core::formatting::format(
+    || generate(&node, text, config),
+    config_to_print_options(text, config),
+  ))
+}
+
 #[cfg(feature = "tracing")]
 pub fn trace_file(_file_path: &Path, text: &str, config: &Configuration) -> dprint_core::formatting::TracingResult {
   let node = parse_node(text).unwrap();
@@ -29,6 +37,10 @@ fn parse_node(text: &str) -> Result<Dockerfile> {
   Ok(Dockerfile::parse(text)?)
 }
 
+fn strip_bom(text: &str) -> &str {
+  text.strip_prefix("\u{FEFF}").unwrap_or(text)
+}
+
 fn config_to_print_options(text: &str, config: &Configuration) -> PrintOptions {
   PrintOptions {
     indent_width: 1,
@@ -37,3 +49,22 @@ fn config_to_print_options(text: &str, config: &Configuration) -> PrintOptions {
     new_line_text: resolve_new_line_kind(text, config.new_line_kind),
   }
 }
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[test]
+  fn strips_bom() {
+    for input_text in ["\u{FEFF}FROM example:12.16.1\n", "\u{FEFF}FROM    example:12.16.1\n"] {
+      let text = format_text(
+        &std::path::PathBuf::from("test.dockerfile"),
+        input_text,
+        &crate::configuration::ConfigurationBuilder::new().build(),
+      )
+      .unwrap()
+      .unwrap();
+      assert_eq!(text, "FROM example:12.16.1\n");
+    }
+  }
+}