Display error messages in the wasm demo (#31)

.github/workflows/CI.yml

@@ -167,7 +167,7 @@ jobs:
             -o ./wasm/uroborosql-fmt.js
             -s ALLOW_MEMORY_GROWTH=1
             -s STACK_SIZE=5MB
-            -s EXPORTED_FUNCTIONS=['_format_sql','_free_format_string']
+            -s EXPORTED_FUNCTIONS=['_format_sql','_get_result_address','_get_error_msg_address']
             -s EXPORTED_RUNTIME_METHODS=ccall
 
       - name: Upload artifact

build.sh

@@ -11,7 +11,7 @@ export EMCC_CFLAGS="-O3
                     -o ./wasm/uroborosql-fmt.js
                     -s ALLOW_MEMORY_GROWTH=1
                     -s STACK_SIZE=5MB
-                    -s EXPORTED_FUNCTIONS=['_format_sql','_free_format_string'] 
+                    -s EXPORTED_FUNCTIONS=['_format_sql','_get_result_address','_get_error_msg_address']
                     -s EXPORTED_RUNTIME_METHODS=ccall"
 # 全体のビルドを実行
 cargo build --package uroborosql-fmt-wasm --target wasm32-unknown-emscripten --release

crates/uroborosql-fmt-wasm/Cargo.toml

@@ -13,4 +13,5 @@ repository.workspace = true
 crate-type = ["cdylib"]
 
 [dependencies]
+once_cell = "1.18.0"
 uroborosql-fmt = { workspace = true }

crates/uroborosql-fmt-wasm/src/lib.rs

@@ -1,7 +1,34 @@
-use std::ffi::{c_char, CStr, CString};
+use once_cell::sync::Lazy;
+use std::{
+    ffi::{c_char, CStr, CString},
+    sync::Mutex,
+};
+
+static RESULT: Lazy<Mutex<CString>> = Lazy::new(|| Mutex::new(CString::new("").unwrap()));
+static ERROR_MSG: Lazy<Mutex<CString>> = Lazy::new(|| Mutex::new(CString::new("").unwrap()));
 
 use uroborosql_fmt::{config::Config, format_sql_with_config};
 
+/// Returns the address of the result string.
+///
+/// # Safety
+///
+/// This is unsafe because it returns a raw pointer.
+#[no_mangle]
+pub unsafe extern "C" fn get_result_address() -> *const c_char {
+    RESULT.lock().unwrap().as_c_str().as_ptr()
+}
+
+/// Returns the address of the error message string.
+///
+/// # Safety
+///
+/// This is unsafe because it returns a raw pointer.
+#[no_mangle]
+pub unsafe extern "C" fn get_error_msg_address() -> *const c_char {
+    ERROR_MSG.lock().unwrap().as_c_str().as_ptr()
+}
+
 /// Formats SQL code given as char pointer `src` by WASM (JavaScript).
 ///
 /// # Safety
@@ -10,31 +37,20 @@ use uroborosql_fmt::{config::Config, format_sql_with_config};
 /// [`CStr::from_ptr`](https://doc.rust-lang.org/stable/std/ffi/struct.CStr.html#method.from_ptr).
 #[export_name = "format_sql"]
 #[no_mangle]
-pub unsafe extern "C" fn format_sql_for_wasm(
-    src: *mut c_char,
-    config_json_str: *mut c_char,
-) -> *mut c_char {
+pub unsafe extern "C" fn format_sql_for_wasm(src: *const c_char, config_json_str: *const c_char) {
+    // Clear previous format result
+    *RESULT.lock().unwrap() = CString::new("").unwrap();
+    *ERROR_MSG.lock().unwrap() = CString::new("").unwrap();
+
     let src = CStr::from_ptr(src).to_str().unwrap().to_owned();
 
     let config_json_str = CStr::from_ptr(config_json_str).to_str().unwrap();
     let config = Config::from_json_str(config_json_str).unwrap();
 
-    // TODO: error handling
-    let result = format_sql_with_config(&src, config).unwrap();
-
-    CString::new(result).unwrap().into_raw()
-}
+    let result = format_sql_with_config(&src, config);
 
-/// Free the string `s` allocated by Rust.
-///
-/// # Safety
-///
-/// This is unsafe because it uses the unsafe function
-/// [`CString::from_war()`](https://doc.rust-lang.org/std/ffi/struct.CString.html#method.from_raw).
-#[no_mangle]
-pub unsafe extern "C" fn free_format_string(s: *mut c_char) {
-    if s.is_null() {
-        return;
+    match result {
+        Ok(result) => *RESULT.lock().unwrap() = CString::new(result).unwrap(),
+        Err(err) => *ERROR_MSG.lock().unwrap() = CString::new(err.to_string()).unwrap(),
     }
-    let _ = CString::from_raw(s);
 }

wasm/index.html

@@ -201,6 +201,8 @@ <h2>Japanese<h2>
     </div>
   </div>
 
+  <div id="error_msg" style="color: red;"></div>
+
   <script src="https://cdnjs.cloudflare.com/ajax/libs/monaco-editor/0.43.0/min/vs/loader.min.js"></script>
   <script src="main.js"></script>
   <script async src="uroborosql-fmt.js"></script>

wasm/ja.html

@@ -197,6 +197,8 @@ <h2>English<h2>
     </div>
   </div>
 
+  <div id="error_msg" style="color: red;"></div>
+
   <script src="https://cdnjs.cloudflare.com/ajax/libs/monaco-editor/0.43.0/min/vs/loader.min.js"></script>
   <script src="main.js"></script>
   <script async src="uroborosql-fmt.js"></script>

wasm/main.js

@@ -221,9 +221,9 @@ function initialize() {
     // タイマースタート
     const startTime = performance.now();
 
-    const ptr = ccall(
+    ccall(
       "format_sql",
-      "number",
+      null,
       ["string", "string"],
       [target, config_str]
     );
@@ -233,13 +233,16 @@ function initialize() {
     // 何ミリ秒かかったかを表示する
     console.log("format complete: " + (endTime - startTime) + "ms");
 
-    // Module.UTF8ToString() でポインタを js の string に変換
-    const res = UTF8ToString(ptr);
+    // Rust側で確保したメモリのポインタを取得
+    const result_ptr = ccall("get_result_address", "number", [], []);
+    const error_ptr = ccall("get_error_msg_address", "number", [], []);
 
-    // Rust 側で確保したフォーマット文字列の所有権を返す
-    ccall("free_format_string", null, ["number"], [ptr]);
+    // Module.UTF8ToString() でポインタを js の string に変換
+    const res = UTF8ToString(result_ptr);
+    const err = UTF8ToString(error_ptr);
 
     dst_editor.setValue(res);
+    document.getElementById("error_msg").innerText = err;
 
     src_editor.updateOptions({ tabSize: tab_size });
     dst_editor.updateOptions({ tabSize: tab_size });