From 18158f5456667f8d258abd1b4ad96625b3edf383 Mon Sep 17 00:00:00 2001
From: Jasper-Bekkers <bekkers@gmail.com>
Date: Tue, 10 Dec 2019 16:12:16 +0100
Subject: [PATCH] Add support for wasm_import_module

---
 src/codegen/mod.rs                            | 18 ++++++++++++++---
 src/lib.rs                                    | 20 +++++++++++++++++++
 src/options.rs                                | 10 ++++++++++
 .../expectations/tests/wasm-import-module.rs  | 13 ++++++++++++
 tests/headers/wasm-import-module.h            |  3 +++
 5 files changed, 61 insertions(+), 3 deletions(-)
 create mode 100644 tests/expectations/tests/wasm-import-module.rs
 create mode 100644 tests/headers/wasm-import-module.h

diff --git a/src/codegen/mod.rs b/src/codegen/mod.rs
index d9ac4aa071..b1612c706a 100644
--- a/src/codegen/mod.rs
+++ b/src/codegen/mod.rs
@@ -3611,10 +3611,22 @@ impl CodeGenerator for Function {
             attributes.push(attributes::link_name(link_name));
         }
 
+        // Unfortunately this can't piggyback on the `attributes` list because
+        // the #[link(wasm_import_module)] needs to happen before the `extern "C"` block.
+        // it doesn't get picked up properly otherwise
+        let wasm_link_attribute =
+            ctx.options().wasm_import_module_name.as_ref().map(|name| {
+                quote! {
+                    #[link(wasm_import_module = #name)]
+                }
+            });
+
         let ident = ctx.rust_ident(canonical_name);
-        let tokens = quote!( extern #abi {
-            #(#attributes)*
-            pub fn #ident ( #( #args ),* ) #ret;
+        let tokens = quote!(
+            #wasm_link_attribute
+            extern #abi {
+                #(#attributes)*
+                pub fn #ident ( #( #args ),* ) #ret;
         });
         result.push(tokens);
     }
diff --git a/src/lib.rs b/src/lib.rs
index 877dbd9adc..a818409be0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -522,6 +522,13 @@ impl Builder {
             output_vector.push("--use-array-pointers-in-arguments".into());
         }
 
+        if let Some(ref wasm_import_module_name) =
+            self.options.wasm_import_module_name
+        {
+            output_vector.push("--wasm-import-module-name".into());
+            output_vector.push(wasm_import_module_name.clone());
+        }
+
         self.options
             .opaque_types
             .get_items()
@@ -1491,6 +1498,15 @@ impl Builder {
         self.options.array_pointers_in_arguments = doit;
         self
     }
+
+    /// Set the wasm import module name
+    pub fn wasm_import_module_name<T: Into<String>>(
+        mut self,
+        import_name: T,
+    ) -> Self {
+        self.options.wasm_import_module_name = Some(import_name.into());
+        self
+    }
 }
 
 /// Configuration options for generated bindings.
@@ -1750,6 +1766,9 @@ struct BindgenOptions {
 
     /// Decide if C arrays should be regular pointers in rust or array pointers
     array_pointers_in_arguments: bool,
+
+    /// Wasm import module name.
+    wasm_import_module_name: Option<String>,
 }
 
 /// TODO(emilio): This is sort of a lie (see the error message that results from
@@ -1875,6 +1894,7 @@ impl Default for BindgenOptions {
             no_copy_types: Default::default(),
             no_hash_types: Default::default(),
             array_pointers_in_arguments: false,
+            wasm_import_module_name: None,
         }
     }
 }
diff --git a/src/options.rs b/src/options.rs
index b09ba91905..01982f13cf 100644
--- a/src/options.rs
+++ b/src/options.rs
@@ -434,6 +434,11 @@ where
             Arg::with_name("use-array-pointers-in-arguments")
                 .long("use-array-pointers-in-arguments")
                 .help("Use `*const [T; size]` instead of `*const T` for C arrays"),
+            Arg::with_name("wasm-import-module-name")
+                .long("wasm-import-module-name")
+                .value_name("name")
+                .takes_value(true)
+                .help("The name to be used in a #[link(wasm_import_module = ...)] statement")
         ]) // .args()
         .get_matches_from(args);
 
@@ -601,6 +606,11 @@ where
         builder = builder.array_pointers_in_arguments(true);
     }
 
+    if let Some(wasm_import_name) = matches.value_of("wasm-import-module-name")
+    {
+        builder = builder.wasm_import_module_name(wasm_import_name);
+    }
+
     if let Some(prefix) = matches.value_of("ctypes-prefix") {
         builder = builder.ctypes_prefix(prefix);
     }
diff --git a/tests/expectations/tests/wasm-import-module.rs b/tests/expectations/tests/wasm-import-module.rs
new file mode 100644
index 0000000000..afbc58462a
--- /dev/null
+++ b/tests/expectations/tests/wasm-import-module.rs
@@ -0,0 +1,13 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+#[link(wasm_import_module = "test-module")]
+extern "C" {
+    pub fn test_function();
+}
\ No newline at end of file
diff --git a/tests/headers/wasm-import-module.h b/tests/headers/wasm-import-module.h
new file mode 100644
index 0000000000..db4fe85c8d
--- /dev/null
+++ b/tests/headers/wasm-import-module.h
@@ -0,0 +1,3 @@
+// bindgen-flags: --wasm-import-module-name test-module
+
+void test_function();
\ No newline at end of file