Auto merge of #543 - th0rex:master, r=emilio

Add option to not add enum name to bitfield or constant variants

Many C libraries prefix the variants of their enums already, because C enums are not scoped. That means if bindgen prefixes them again that can lead to ugly names like `cs_arch_CS_ARCH_ARM`. The `cs_arch_` part comes from the name of the enum itself and `CS_ARCH_ARM` is the name of the actual variant.

This pull request introduces a variable for changing this behaviour, alongside command line flags and a test case. If `prepend_enum_names` is set to false the resulting variant name will be `CS_ARCH_ARM` instead of `cs_arch_CS_ARCH_ARM` as it is now.

If there is anything that could be improved, or this toggle already exists (I have not found anything like that), please let me know.

src/codegen/mod.rs

@@ -1993,10 +1993,14 @@ impl CodeGenerator for Enum {
             Some(item.parent_id().canonical_name(ctx))
         };
 
-        let constant_mangling_prefix = if enum_ty.name().is_none() {
-            parent_canonical_name.as_ref().map(|n| &*n)
+        let constant_mangling_prefix = if ctx.options().prepend_enum_name {
+            if enum_ty.name().is_none() {
+                parent_canonical_name.as_ref().map(|n| &*n)
+            } else {
+                Some(&name)
+            }
         } else {
-            Some(&name)
+            None
         };
 
         // NB: We defer the creation of constified variants, in case we find

src/lib.rs

@@ -458,6 +458,12 @@ impl Builder {
         self
     }
 
+    /// Prepend the enum name to constant or bitfield variants.
+    pub fn prepend_enum_name(mut self, doit: bool) -> Self {
+        self.options.prepend_enum_name = doit;
+        self
+    }
+
     /// Generate the Rust bindings using the options built up thus far.
     pub fn generate<'ctx>(self) -> Result<Bindings<'ctx>, ()> {
         Bindings::generate(self.options, None)
@@ -593,6 +599,9 @@ pub struct BindgenOptions {
     ///
     /// [1]: https://github.com/servo/rust-bindgen/issues/528
     pub enable_mangling: bool,
+
+    /// Whether to prepend the enum name to bitfield or constant variants.
+    pub prepend_enum_name: bool,
 }
 
 /// TODO(emilio): This is sort of a lie (see the error message that results from
@@ -648,6 +657,7 @@ impl Default for BindgenOptions {
             whitelist_recursively: true,
             objc_extern_crate: false,
             enable_mangling: true,
+            prepend_enum_name: true,
         }
     }
 }

src/options.rs

@@ -127,6 +127,9 @@ pub fn builder_from_flags<I>
             Arg::with_name("no-convert-floats")
                 .long("no-convert-floats")
                 .help("Don't automatically convert floats to f32/f64."),
+            Arg::with_name("no-prepend-enum-name")
+                .long("no-prepend-enum-name")
+                .help("Do not prepend the enum name to bitfield or constant variants"),
             Arg::with_name("no-unstable-rust")
                 .long("no-unstable-rust")
                 .help("Do not generate unstable Rust code.")
@@ -239,6 +242,10 @@ pub fn builder_from_flags<I>
         builder = builder.derive_default(false);
     }
 
+    if matches.is_present("no-prepend-enum-name") {
+        builder = builder.prepend_enum_name(false);
+    }
+
     if let Some(prefix) = matches.value_of("ctypes-prefix") {
         builder = builder.ctypes_prefix(prefix);
     }

tests/expectations/tests/prepend_enum_name.rs

@@ -0,0 +1,9 @@
+/* automatically generated by rust-bindgen */
+
+
+#![allow(non_snake_case)]
+
+
+pub const FOO_BAR: foo = 0;
+pub const FOO_BAZ: foo = 1;
+pub type foo = ::std::os::raw::c_uint;

tests/headers/prepend_enum_name.hpp

@@ -0,0 +1,6 @@
+// bindgen-flags: --constified-enum foo --no-prepend-enum-name
+
+enum foo {
+	FOO_BAR,
+	FOO_BAZ,
+};