feat(es/minifier): Allow disabling char frequency analysis (#10259)

**Description:**

This is required for next.js

Author: kdy1

.changeset/tasty-lies-notice.md

@@ -0,0 +1,5 @@
+---
+swc_ecma_minifier: major
+---
+
+feat(es/minifier): Allow disabling char frequency analysis

crates/swc_ecma_minifier/src/lib.rs

@@ -227,12 +227,16 @@ pub fn optimize(
 
         let preserved = idents_to_preserve(mangle, marks, &n);
 
-        let chars = CharFreq::compute(
-            &n,
-            &preserved,
-            SyntaxContext::empty().apply_mark(marks.unresolved_mark),
-        )
-        .compile();
+        let chars = if !mangle.disable_char_freq {
+            CharFreq::compute(
+                &n,
+                &preserved,
+                SyntaxContext::empty().apply_mark(marks.unresolved_mark),
+            )
+            .compile()
+        } else {
+            CharFreq::default().compile()
+        };
 
         mangle_names(
             &mut n,

crates/swc_ecma_minifier/src/option/mod.rs

@@ -90,6 +90,10 @@ pub struct MangleOptions {
     /// mangle names visible in scopes where eval or with are used
     #[serde(default)]
     pub eval: bool,
+
+    /// Disable char frequency analysis.
+    #[serde(default)]
+    pub disable_char_freq: bool,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize, Merge)]

crates/swc_ecma_minifier/tests/fixture/simple/disable-char-freq/1/input.js

@@ -0,0 +1,4 @@
+
+var foo;
+var bar = 2;
+var baz;

crates/swc_ecma_minifier/tests/fixture/simple/disable-char-freq/1/mangle.json

@@ -0,0 +1,4 @@
+{
+    "disableCharFreq": true,
+    "toplevel": true
+}

crates/swc_ecma_minifier/tests/fixture/simple/disable-char-freq/1/output.js

@@ -0,0 +1 @@
+var a, b, c = 2;