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>

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