fix(es/minifier): Fix if_return bug related to await and yield (#…

…8328)

**Related issue:**

 - Closes #8324

crates/swc/tests/fixture/issues-8xxx/8324/input/.swcrc

@@ -0,0 +1,65 @@
+{
+    "jsc": {
+        "parser": {
+            "syntax": "ecmascript",
+            "jsx": false
+        },
+        "target": "es2022",
+        "loose": false,
+        "minify": {
+            "compress": {
+                "arguments": false,
+                "arrows": false,
+                "booleans": false,
+                "booleans_as_integers": false,
+                "collapse_vars": false,
+                "comparisons": false,
+                "computed_props": false,
+                "conditionals": false,
+                "dead_code": false,
+                "directives": false,
+                "drop_console": false,
+                "drop_debugger": false,
+                "evaluate": false,
+                "expression": false,
+                "hoist_funs": false,
+                "hoist_props": false,
+                "hoist_vars": false,
+                "if_return": true,
+                "join_vars": false,
+                "keep_classnames": false,
+                "keep_fargs": false,
+                "keep_fnames": false,
+                "keep_infinity": false,
+                "loops": false,
+                "negate_iife": false,
+                "properties": false,
+                "reduce_funcs": false,
+                "reduce_vars": false,
+                "side_effects": false,
+                "switches": false,
+                "typeofs": false,
+                "unsafe": false,
+                "unsafe_arrows": false,
+                "unsafe_comps": false,
+                "unsafe_Function": false,
+                "unsafe_math": false,
+                "unsafe_symbols": false,
+                "unsafe_methods": false,
+                "unsafe_proto": false,
+                "unsafe_regexp": false,
+                "unsafe_undefined": false,
+                "unused": false,
+                "const_to_let": false,
+                "pristine_globals": false,
+                "passes": 3
+            },
+            "mangle": false
+        }
+    },
+    "module": {
+        "type": "es6"
+    },
+    "minify": false,
+    "isModule": true
+}

crates/swc/tests/fixture/issues-8xxx/8324/input/1.js

@@ -0,0 +1,24 @@
+function Deferred() {
+    const deferred = this;
+    deferred.promise = new Promise(function (resolve, reject) {
+        deferred.resolve = resolve;
+        deferred.reject = reject;
+    });
+}
+
+export async function bug() {
+    const s = `next`;
+    if (!window[s]) {
+        for (window[s] = new Deferred(); ;)
+            if (window.current) await window.current.promise;
+            else {
+                window.current = window[s];
+                try {
+                    return await window[s].promise // This line compressed to 'break'. I guess compressor intended jump to 23 line which is looks like same code.
+                } finally {
+                    delete window.current // Above 'break' makes unintended delete
+                }
+            }
+    }
+    return await window[s].promise
+}

crates/swc/tests/fixture/issues-8xxx/8324/output/1.js

@@ -0,0 +1,19 @@
+function Deferred() {
+    const deferred = this;
+    deferred.promise = new Promise(function(resolve, reject) {
+        deferred.resolve = resolve, deferred.reject = reject;
+    });
+}
+export async function bug() {
+    const s = "next";
+    if (!window[s]) for(window[s] = new Deferred();;)if (window.current) await window.current.promise;
+    else {
+        window.current = window[s];
+        try {
+            return await window[s].promise;
+        } finally{
+            delete window.current;
+        }
+    }
+    return await window[s].promise;
+}

crates/swc_ecma_minifier/src/compress/pure/dead_code.rs

@@ -6,7 +6,11 @@ use swc_ecma_utils::{extract_var_ids, ExprExt, StmtExt, StmtLike, Value};
 use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
 
 use super::Pure;
-use crate::{compress::util::is_fine_for_if_cons, maybe_par, util::ModuleItemExt};
+use crate::{
+    compress::util::is_fine_for_if_cons,
+    maybe_par,
+    util::{contains_await_or_yield, ModuleItemExt},
+};
 
 /// Methods related to option `dead_code`.
 impl Pure<'_> {
@@ -285,6 +289,10 @@ impl Pure<'_> {
             _ => return,
         };
 
+        if contains_await_or_yield(last) {
+            return;
+        }
+
         fn drop<T: StmtLike>(stmt: &mut T, last: &Stmt, need_break: bool) -> bool {
             match stmt.as_stmt_mut() {
                 Some(s) if s.eq_ignore_span(last) => {

crates/swc_ecma_minifier/src/util/mod.rs

@@ -211,6 +211,7 @@ where
 
 #[derive(Default)]
 pub(crate) struct LeapFinder {
+    found_await: bool,
     found_yield: bool,
     found_continue_with_label: bool,
     target_label: Option<Id>,
@@ -219,6 +220,12 @@ pub(crate) struct LeapFinder {
 impl Visit for LeapFinder {
     noop_visit_type!();
 
+    fn visit_await_expr(&mut self, n: &AwaitExpr) {
+        n.visit_children_with(self);
+
+        self.found_await = true;
+    }
+
     fn visit_arrow_expr(&mut self, _: &ArrowExpr) {}
 
     fn visit_class_method(&mut self, _: &ClassMethod) {}
@@ -249,6 +256,16 @@ impl Visit for LeapFinder {
     }
 }
 
+#[allow(unused)]
+pub(crate) fn contains_await_or_yield<N>(n: &N) -> bool
+where
+    N: VisitWith<LeapFinder>,
+{
+    let mut v = LeapFinder::default();
+    n.visit_with(&mut v);
+    v.found_yield || v.found_await
+}
+
 /// This method returns true only if `T` is `var`. (Not `const` or `let`)
 pub(crate) fn is_hoisted_var_decl_without_init<T>(t: &T) -> bool
 where

crates/swc_ecma_minifier/tests/fixture/issues/8324/config.json

@@ -0,0 +1,5 @@
+{
+    "defaults": false,
+    "if_return": true,
+    "passes": 3
+}

crates/swc_ecma_minifier/tests/fixture/issues/8324/input.js

@@ -0,0 +1,24 @@
+function Deferred() {
+    const deferred = this;
+    deferred.promise = new Promise(function (resolve, reject) {
+        deferred.resolve = resolve;
+        deferred.reject = reject;
+    });
+}
+
+export async function bug() {
+    const s = `next`;
+    if (!window[s]) {
+        for (window[s] = new Deferred(); ;)
+            if (window.current) await window.current.promise;
+            else {
+                window.current = window[s];
+                try {
+                    return await window[s].promise // This line compressed to 'break'. I guess compressor intended jump to 23 line which is looks like same code.
+                } finally {
+                    delete window.current // Above 'break' makes unintended delete
+                }
+            }
+    }
+    return await window[s].promise
+}

crates/swc_ecma_minifier/tests/fixture/issues/8324/output.js

@@ -0,0 +1,22 @@
+function Deferred() {
+    const deferred = this;
+    deferred.promise = new Promise(function(resolve, reject) {
+        deferred.resolve = resolve;
+        deferred.reject = reject;
+    });
+}
+export async function bug() {
+    const s = "next";
+    if (!window[s]) {
+        for(window[s] = new Deferred();;)if (window.current) await window.current.promise;
+        else {
+            window.current = window[s];
+            try {
+                return await window[s].promise;
+            } finally{
+                delete window.current;
+            }
+        }
+    }
+    return await window[s].promise;
+}