feat(es/minifier): Respect more options (#8582)

**Description:**

This PR makes the ES minifier respect more options.

Changes:
 - `reduce_vars` now enables IIFE invoker.
 - `reduce_vars` now enables seq inliner.
 - `top_retain` is now respected by seq inliner.
 - `arguments` is now ignored by seq inliner.

---------

Co-authored-by: austaras <austaras@outlook.com>

Author: kdy1

crates/swc_ecma_minifier/src/compress/optimize/iife.rs

@@ -430,7 +430,9 @@ impl Optimizer<'_> {
     pub(super) fn invoke_iife(&mut self, e: &mut Expr) {
         trace_op!("iife: invoke_iife");
 
-        if self.options.inline == 0 {
+        if self.options.inline == 0
+            && !(self.options.reduce_vars && self.options.reduce_fns && self.options.evaluate)
+        {
             let skip = match e {
                 Expr::Call(v) => !v.callee.span().is_dummy(),
                 _ => true,

crates/swc_ecma_minifier/src/compress/optimize/mod.rs

@@ -31,7 +31,7 @@ use crate::{
     maybe_par,
     mode::Mode,
     option::{CompressOptions, MangleOptions},
-    program_data::ProgramData,
+    program_data::{ProgramData, VarUsageInfo},
     util::{
         contains_eval, contains_leaping_continue_with_label, make_number, ExprOptExt, ModuleItemExt,
     },
@@ -323,7 +323,7 @@ impl From<&Function> for FnMetadata {
 
 impl Optimizer<'_> {
     fn may_remove_ident(&self, id: &Ident) -> bool {
-        if self.ctx.is_exported {
+        if let Some(VarUsageInfo { exported: true, .. }) = self.data.vars.get(&id.clone().to_id()) {
             return false;
         }
 
@@ -2041,6 +2041,7 @@ impl VisitMut for Optimizer<'_> {
 
         let ctx = Ctx {
             top_level: false,
+            in_fn_like: true,
             is_lhs_of_assign: false,
             is_exact_lhs_of_assign: false,
             ..self.ctx
@@ -2062,7 +2063,14 @@ impl VisitMut for Optimizer<'_> {
             }
         }
 
-        e.visit_mut_children_with(self);
+        let ctx = Ctx {
+            top_level: false,
+            in_fn_like: true,
+            is_lhs_of_assign: false,
+            is_exact_lhs_of_assign: false,
+            ..self.ctx
+        };
+        e.visit_mut_children_with(&mut *self.with_ctx(ctx));
     }
 
     #[cfg_attr(feature = "debug", tracing::instrument(skip_all))]

crates/swc_ecma_minifier/src/compress/optimize/sequences.rs

@@ -557,7 +557,16 @@ impl Optimizer<'_> {
         options: &CompressOptions,
     ) -> Option<Vec<Mergable<'a>>> {
         Some(match s {
-            Stmt::Expr(e) => vec![Mergable::Expr(&mut e.expr)],
+            Stmt::Expr(e) => {
+                if self.options.sequences()
+                    || self.options.collapse_vars
+                    || self.options.side_effects
+                {
+                    vec![Mergable::Expr(&mut e.expr)]
+                } else {
+                    return None;
+                }
+            }
             Stmt::Decl(Decl::Var(v)) => {
                 if options.reduce_vars || options.collapse_vars {
                     v.decls.iter_mut().map(Mergable::Var).collect()
@@ -612,7 +621,7 @@ impl Optimizer<'_> {
     where
         T: ModuleItemExt,
     {
-        if !self.options.sequences() && !self.options.collapse_vars {
+        if !self.options.sequences() && !self.options.collapse_vars && !self.options.reduce_vars {
             log_abort!("sequences: [x] Disabled");
             return;
         }
@@ -1513,6 +1522,16 @@ impl Optimizer<'_> {
             )
         };
 
+        // Respect top_retain
+        if let Some(a_id) = a.id() {
+            if a_id.0 == "arguments"
+                || (matches!(a, Mergable::Var(_) | Mergable::FnDecl(_))
+                    && !self.may_remove_ident(&Ident::from(a_id)))
+            {
+                return Ok(false);
+            }
+        }
+
         if match &*b {
             Expr::Arrow(..)
             | Expr::Fn(..)

crates/swc_ecma_minifier/tests/TODO.txt

@@ -43,7 +43,6 @@ collapse_vars/issue_1858/input.js
 collapse_vars/issue_2187_2/input.js
 collapse_vars/issue_2203_2/input.js
 collapse_vars/issue_2203_4/input.js
-collapse_vars/issue_2298/input.js
 collapse_vars/issue_2319_1/input.js
 collapse_vars/issue_2319_3/input.js
 collapse_vars/issue_2436_1/input.js
@@ -119,11 +118,8 @@ drop_unused/issue_2660_2/input.js
 drop_unused/issue_2665/input.js
 drop_unused/issue_2846/input.js
 drop_unused/issue_t161_top_retain_10/input.js
-drop_unused/issue_t161_top_retain_11/input.js
 drop_unused/issue_t161_top_retain_12/input.js
 drop_unused/issue_t161_top_retain_15/input.js
-drop_unused/issue_t161_top_retain_8/input.js
-drop_unused/issue_t161_top_retain_9/input.js
 drop_unused/issue_t183/input.js
 drop_unused/keep_assign/input.js
 drop_unused/reassign_const/input.js
@@ -159,7 +155,6 @@ functions/issue_2107/input.js
 functions/issue_2114_1/input.js
 functions/issue_2114_2/input.js
 functions/issue_2601_2/input.js
-functions/issue_2604_2/input.js
 functions/issue_2620_2/input.js
 functions/issue_2620_3/input.js
 functions/issue_2630_2/input.js
@@ -297,13 +292,8 @@ reduce_vars/iife/input.js
 reduce_vars/iife_new/input.js
 reduce_vars/inner_var_for_2/input.js
 reduce_vars/inverted_var/input.js
-reduce_vars/issue_1595_3/input.js
-reduce_vars/issue_1670_2/input.js
-reduce_vars/issue_1670_4/input.js
-reduce_vars/issue_1670_5/input.js
 reduce_vars/issue_1850_2/input.js
 reduce_vars/issue_2485/input.js
-reduce_vars/issue_2757_1/input.js
 reduce_vars/issue_2799_2/input.js
 reduce_vars/issue_2836/input.js
 reduce_vars/issue_2860_2/input.js

crates/swc_ecma_minifier/tests/fixture/next/56408/output.js

@@ -188,6 +188,7 @@ collapse_vars/issue_2203_1/input.js
 collapse_vars/issue_2203_3/input.js
 collapse_vars/issue_2250_1/input.js
 collapse_vars/issue_2250_2/input.js
+collapse_vars/issue_2298/input.js
 collapse_vars/issue_2313_1/input.js
 collapse_vars/issue_2313_2/input.js
 collapse_vars/issue_2319_2/input.js
@@ -459,6 +460,7 @@ drop_unused/issue_3192/input.js
 drop_unused/issue_805_1/input.js
 drop_unused/issue_805_2/input.js
 drop_unused/issue_t161_top_retain_1/input.js
+drop_unused/issue_t161_top_retain_11/input.js
 drop_unused/issue_t161_top_retain_13/input.js
 drop_unused/issue_t161_top_retain_14/input.js
 drop_unused/issue_t161_top_retain_2/input.js
@@ -467,6 +469,8 @@ drop_unused/issue_t161_top_retain_4/input.js
 drop_unused/issue_t161_top_retain_5/input.js
 drop_unused/issue_t161_top_retain_6/input.js
 drop_unused/issue_t161_top_retain_7/input.js
+drop_unused/issue_t161_top_retain_8/input.js
+drop_unused/issue_t161_top_retain_9/input.js
 drop_unused/keep_fnames/input.js
 drop_unused/unused_block_decls/input.js
 drop_unused/unused_block_decls_in_catch/input.js
@@ -624,6 +628,7 @@ functions/issue_2531_2/input.js
 functions/issue_2531_3/input.js
 functions/issue_2601_1/input.js
 functions/issue_2604_1/input.js
+functions/issue_2604_2/input.js
 functions/issue_2616/input.js
 functions/issue_2620_1/input.js
 functions/issue_2620_4/input.js
@@ -1308,10 +1313,14 @@ reduce_vars/issue_1533_1/input.js
 reduce_vars/issue_1533_2/input.js
 reduce_vars/issue_1595_1/input.js
 reduce_vars/issue_1595_2/input.js
+reduce_vars/issue_1595_3/input.js
 reduce_vars/issue_1595_4/input.js
 reduce_vars/issue_1606/input.js
 reduce_vars/issue_1670_1/input.js
+reduce_vars/issue_1670_2/input.js
 reduce_vars/issue_1670_3/input.js
+reduce_vars/issue_1670_4/input.js
+reduce_vars/issue_1670_5/input.js
 reduce_vars/issue_1670_6/input.js
 reduce_vars/issue_1814_1/input.js
 reduce_vars/issue_1814_2/input.js
@@ -1352,6 +1361,7 @@ reduce_vars/issue_2496/input.js
 reduce_vars/issue_2598/input.js
 reduce_vars/issue_2669/input.js
 reduce_vars/issue_2670/input.js
+reduce_vars/issue_2757_1/input.js
 reduce_vars/issue_2757_2/input.js
 reduce_vars/issue_2774/input.js
 reduce_vars/issue_2799_1/input.js

crates/swc_ecma_minifier/tests/passing.txt

@@ -4,7 +4,7 @@ class Alpha {
     }
 }
 let x = 2, z = 4;
-console.log(2, 3, 4, 6, 8, 12, 2, 3, 4, new Alpha().num(), new class {
+console.log(2, 3, z, 6, 2 * z, 3 * z, 2, 3, z, new Alpha().num(), new class {
     num() {
         return 3;
     }

crates/swc_ecma_minifier/tests/terser/compress/drop_unused/issue_t161_top_retain_14/output.js

@@ -1 +1,4 @@
-console.log(2, 3);
+function f() {
+    return 2;
+}
+console.log(f(), 3);

crates/swc_ecma_minifier/tests/terser/compress/drop_unused/issue_t161_top_retain_3/output.js

@@ -1,6 +1,5 @@
 function f() {
-    var a = (function () {
+    return (function() {
         return x();
-    })();
-    return a(42);
+    })()(42);
 }

crates/swc_ecma_minifier/tests/terser/compress/drop_unused/vardef_value/output.js

@@ -1,12 +1,11 @@
 (function(outputs) {
     var handlers = [];
     for(var i = 0; i < outputs.length; i++){
-        var output = outputs[i];
         var handleEventClosure = function(eventName) {
             return function() {
                 return console.log(eventName);
             };
-        }(output.eventName);
+        }(outputs[i].eventName);
         handlers.push(handleEventClosure);
     }
     return handlers;

crates/swc_ecma_minifier/tests/terser/compress/functions/issue_2663_3/output.js

@@ -1,14 +1,11 @@
 (function() {
     (function() {
-        {
-            const data = function(data) {
-                return data[data[0]];
-            }([
-                1,
-                2,
-                3
-            ]);
-            console.log(data);
-        }
+        console.log(function(data) {
+            return data[data[0]];
+        }([
+            1,
+            2,
+            3
+        ]));
     })();
 })();

crates/swc_ecma_minifier/tests/terser/compress/functions/issue_2842/output.js

@@ -1,5 +1 @@
-(function () {
-    (function () {
-        f(1).bar = 1;
-    })();
-})();
+f(1).bar = 1;

crates/swc_ecma_minifier/tests/terser/compress/issue_1609/chained_evaluation_1/output.js

@@ -1,6 +1,4 @@
-(function () {
-    (function () {
-        var b = "long piece of string";
-        f(b).bar = b;
-    })();
+(function() {
+    var b;
+    b = "long piece of string", f(b).bar = b;
 })();

crates/swc_ecma_minifier/tests/terser/compress/issue_1609/chained_evaluation_2/output.js

@@ -1,4 +1,2 @@
 var b = 10;
-!function() {
-    b = 100;
-}(), console.log(100, b);
+console.log(100, b = 100);

crates/swc_ecma_minifier/tests/terser/compress/issue_1656/f7/output.js

@@ -1,4 +1,4 @@
-!(function () {
+!function() {
     var a;
     console.log(a);
-})();
+}();

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/boolean_binary_assign/output.js

@@ -1,4 +1,4 @@
-!(function () {
+!function() {
     var a;
     console.log(a);
-})();
+}();

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/cond_assign/output.js

@@ -3,10 +3,7 @@ function f() {
         x();
         return a;
     }
-    var a = function() {
-        y();
-        return 2;
-    }();
+    var a = (y(), 2);
     var b = 2;
     return a + 2;
 }

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/defun_reference/output.js

@@ -1,10 +1 @@
-!(function () {
-    var a = 1,
-        b = 0;
-    !(function () {
-        b++;
-        return;
-        a = 2;
-    })();
-    console.log(a);
-})();
+console.log(1);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/iife_assign/output.js

@@ -1,3 +1 @@
-!(function () {
-    console.log("test".indexOf("e"));
-})();
+console.log("test".indexOf("e"));

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/immutable/output.js

@@ -1,11 +1,7 @@
 function f() {
-    var a = 1,
-        b = 2;
-    for (b in (function () {
-        return x(1, b, c);
-    })()) {
-        var c = 3,
-            d = 4;
+    var a = 1, b = 2;
+    for(b in x(1, b, c)){
+        var c = 3, d = 4;
         x(1, b, c, d);
     }
     x(1, b, c, d);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/inner_var_for_in_1/output.js

@@ -1,3 +1 @@
-(function(a) {
-    return g(3);
-})(0);
+g(3);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1595_2/output.js

@@ -1,3 +1 @@
-(function (a) {
-    return g(3);
-})();
+g(3);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1595_3/output.js

@@ -1,4 +1 @@
-(function () {
-    var a;
-    void 0 === a ? console.log("PASS") : console.log("FAIL");
-})();
+console.log("PASS");

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1670_1/output.js

@@ -1,3 +1 @@
-(function () {
-    console.log("PASS");
-})();
+console.log("PASS");

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1670_2/output.js

@@ -1,4 +1 @@
-(function () {
-    var a;
-    void 0 === a ? console.log("PASS") : console.log("FAIL");
-})();
+console.log("PASS");

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1670_3/output.js

@@ -1,3 +1 @@
-(function () {
-    console.log("PASS");
-})();
+console.log("PASS");

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1670_4/output.js

@@ -1,3 +1 @@
-(function () {
-    console.log(1);
-})();
+console.log(1);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1670_5/output.js

@@ -1,6 +1,5 @@
 const a = 42;
 !function() {
-    !function(a) {
-        console.log(a++, 42);
-    }(0);
+    var a;
+    a = 0, console.log(a++, 42);
 }();

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1814_1/output.js

@@ -1,6 +1,5 @@
 const a = "32";
 !function() {
-    !function(a) {
-        console.log("321", a++);
-    }(0);
+    var a;
+    a = 0, console.log("321", a++);
 }();

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/issue_1814_2/output.js

@@ -1,3 +1,3 @@
-var b = 1;
-var a = b += 1, b = NaN;
+var b;
+var a = b = 2, b = NaN;
 console.log(a, b);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/lvalues_def_2/output.js

@@ -1,5 +1,3 @@
 var x = 3;
-do (function() {
-    console.log("bar:", --x);
-})();
+do console.log("bar:", --x);
 while (x)

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/toplevel_on_loops_1/output.js

@@ -1,3 +1 @@
-for(;;)(function() {
-    console.log("bar:");
-})();
+for(;;)console.log("bar:");

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/toplevel_on_loops_2/output.js

@@ -1,3 +1 @@
-!(function () {
-    console.log(2);
-})();
+console.log(2);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/var_assign_1/output.js

@@ -1,3 +1 @@
-!function() {
-    console.log(2);
-}();
+console.log(2);

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/var_assign_2/output.js

@@ -1,6 +1,5 @@
 !function() {
     var a;
-    !function(b) {
-        console.log(a = 2, b);
-    }(a);
+    var b;
+    b = a, console.log(a = 2, b);
 }();

crates/swc_ecma_minifier/tests/terser/compress/reduce_vars/var_assign_5/output.js

@@ -1,4 +1,4 @@
-!(function () {
-    var a = (function () {})((a = 1));
+!function() {
+    var a = void (a = 1);
     console.log(a);
-})();
+}();