#[swift_bridge(already_declared)] causes duplicate header definitions

Here's an example. In lib.rs I have:

#[swift_bridge::bridge]
mod ffi {
    #[derive(Debug)]
    #[swift_bridge(swift_name = "MinimuxerError")]
    enum Errors {
        ...
    }

    extern "Rust" {
        ...
    }
}

In another module, I have:

#[swift_bridge::bridge]
mod ffi {
    #[swift_bridge(already_declared, swift_name = "MinimuxerError")]
    enum Errors {}

    extern "Rust" {
        fn cool_function() -> Result<(), Errors>;
    }
}

In another module, I have:

#[swift_bridge::bridge]
mod ffi {
    #[swift_bridge(already_declared, swift_name = "MinimuxerError")]
    enum Errors {}

    extern "Rust" {
        fn another_cool_function() -> Result<(), Errors>;
    }
}

This causes duplicate header definitions (ResultVoidAndErrors$Tag):

// File automatically generated by swift-bridge.
#include <stdint.h>
struct __swift_bridge__$ResultVoidAndErrors __swift_bridge__$another_cool_function();
typedef enum __swift_bridge__$ResultVoidAndErrors$Tag {__swift_bridge__$ResultVoidAndErrors$ResultOk, __swift_bridge__$ResultVoidAndErrors$ResultErr} __swift_bridge__$ResultVoidAndErrors$Tag;
union __swift_bridge__$ResultVoidAndErrors$Fields {struct __swift_bridge__$Errors err;};
typedef struct __swift_bridge__$ResultVoidAndErrors{__swift_bridge__$ResultVoidAndErrors$Tag tag; union __swift_bridge__$ResultVoidAndErrors$Fields payload;} __swift_bridge__$ResultVoidAndErrors;

// File automatically generated by swift-bridge.
#include <stdint.h>
struct __swift_bridge__$ResultVoidAndErrors __swift_bridge__$cool_function();
typedef enum __swift_bridge__$ResultVoidAndErrors$Tag {__swift_bridge__$ResultVoidAndErrors$ResultOk, __swift_bridge__$ResultVoidAndErrors$ResultErr} __swift_bridge__$ResultVoidAndErrors$Tag;
union __swift_bridge__$ResultVoidAndErrors$Fields {struct __swift_bridge__$MinimuxerError err;};
typedef struct __swift_bridge__$ResultVoidAndErrors{__swift_bridge__$ResultVoidAndErrors$Tag tag; union __swift_bridge__$ResultVoidAndErrors$Fields payload;} __swift_bridge__$ResultVoidAndErrors;

// File automatically generated by swift-bridge.
#include <stdbool.h>
typedef enum __swift_bridge__$MinimuxerErrorTag { ... } __swift_bridge__$MinimuxerErrorTag;
typedef struct __swift_bridge__$MinimuxerError { __swift_bridge__$MinimuxerErrorTag tag; } __swift_bridge__$MinimuxerError;
typedef struct __swift_bridge__$Option$MinimuxerError { bool is_some; __swift_bridge__$MinimuxerError val; } __swift_bridge__$Option$MinimuxerError;
void* __swift_bridge__$MinimuxerError$Debug(__swift_bridge__$MinimuxerError this);
void* __swift_bridge__$Vec_MinimuxerError$new(void);
void __swift_bridge__$Vec_MinimuxerError$drop(void* vec_ptr);
void __swift_bridge__$Vec_MinimuxerError$push(void* vec_ptr, __swift_bridge__$MinimuxerError item);
__swift_bridge__$Option$MinimuxerError __swift_bridge__$Vec_MinimuxerError$pop(void* vec_ptr);
__swift_bridge__$Option$MinimuxerError __swift_bridge__$Vec_MinimuxerError$get(void* vec_ptr, uintptr_t index);
__swift_bridge__$Option$MinimuxerError __swift_bridge__$Vec_MinimuxerError$get_mut(void* vec_ptr, uintptr_t index);
uintptr_t __swift_bridge__$Vec_MinimuxerError$len(void* vec_ptr);
void* __swift_bridge__$Vec_MinimuxerError$as_ptr(void* vec_ptr);

which Xcode then complains about.

A workaround is to add this to your build script:

// out_dir is probably `./generated/{crate name}/`
for path in std::fs::read_dir(out_dir).unwrap() {
    let path = path
        .unwrap()
        .path()
        .file_name()
        .unwrap()
        .to_str()
        .unwrap()
        .to_string();
    let out_path = format!("{out_dir}{path}");

    // remove duplicate lines from minimuxer.h (see https://github.com/chinedufn/swift-bridge/issues/207)
    if path.ends_with(&format!("{}.h", env!("CARGO_PKG_NAME"))) {
        let input = std::fs::read_to_string(&out_path)
            .unwrap()
            // sometimes swift-bridge won't add a newline after defintions
            .replace(";typedef", ";\ntypedef");
        let mut output: Vec<String> = vec![];
        for line in input.split("\n") {
            let line = line.to_owned();
            if !output.contains(&line) || line.len() <= 0 || line.starts_with("//") {
                output.push(line);
            }
        }
        std::fs::write(&out_path, output.join("\n")).unwrap();
    }
}

chinedufn / swift-bridge

#[swift_bridge(already_declared)] causes duplicate header definitions #207