Add a feature to make which dependency optional

Cargo.toml

@@ -54,7 +54,7 @@ lazy_static = "1"
 peeking_take_while = "0.1.2"
 quote = { version = "1", default-features = false }
 regex = "1.0"
-which = ">=1.0, <3.0"
+which = { version = ">=1.0, <3.0", optional = true }
 shlex = "0.1"
 fxhash = "0.2"
 # New validation in 0.3.6 breaks bindgen-integration:
@@ -70,9 +70,11 @@ optional = true
 version = "0.4"
 
 [features]
-default = ["logging", "clap"]
+default = ["logging", "clap", "which-rustfmt"]
 logging = ["env_logger", "log"]
 static = []
+# Dynamically discover a `rustfmt` binary using the `which` crate
+which-rustfmt = ["which"]
 
 # These features only exist for CI testing -- don't use them if you're not hacking
 # on bindgen!

src/lib.rs

@@ -32,6 +32,7 @@ extern crate quote;
 extern crate proc_macro2;
 extern crate regex;
 extern crate shlex;
+#[cfg(feature = "which-rustfmt")]
 extern crate which;
 
 #[cfg(feature = "logging")]
@@ -1900,18 +1901,21 @@ impl Bindings {
     }
 
     /// Gets the rustfmt path to rustfmt the generated bindings.
-    fn rustfmt_path<'a>(&'a self) -> io::Result<Cow<'a, PathBuf>> {
+    fn rustfmt_path<'a>(&'a self) -> io::Result<Option<Cow<'a, PathBuf>>> {
         debug_assert!(self.options.rustfmt_bindings);
         if let Some(ref p) = self.options.rustfmt_path {
-            return Ok(Cow::Borrowed(p));
+            return Ok(Some(Cow::Borrowed(p)));
         }
         if let Ok(rustfmt) = env::var("RUSTFMT") {
-            return Ok(Cow::Owned(rustfmt.into()));
+            return Ok(Some(Cow::Owned(rustfmt.into())));
         }
+        #[cfg(feature = "which-rustfmt")]
         match which::which("rustfmt") {
-            Ok(p) => Ok(Cow::Owned(p)),
+            Ok(p) => Ok(Some(Cow::Owned(p))),
             Err(e) => Err(io::Error::new(io::ErrorKind::Other, format!("{}", e))),
         }
+        #[cfg(not(feature = "which-rustfmt"))]
+        Ok(None)
     }
 
     /// Checks if rustfmt_bindings is set and runs rustfmt on the string
@@ -1926,7 +1930,11 @@ impl Bindings {
             return Ok(Cow::Borrowed(source));
         }
 
-        let rustfmt = self.rustfmt_path()?;
+        let rustfmt = if let Some(rustfmt) = self.rustfmt_path()? {
+            rustfmt
+        } else {
+            return Ok(Cow::Borrowed(source));
+        };
         let mut cmd = Command::new(&*rustfmt);
 
         cmd