fix(es/minifier): Check exported when optimize last expr (#10939)

**Related issue:**

 - Closes #10935

Author: Austaras

.changeset/honest-geese-rest.md

@@ -0,0 +1,6 @@
+---
+swc_core: patch
+swc_ecma_minifier: patch
+---
+
+fix(es/minifier): Check exported when optimize last expr

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

@@ -2,7 +2,7 @@ use swc_common::util::take::Take;
 use swc_ecma_ast::*;
 
 use super::{BitCtx, Optimizer};
-use crate::program_data::VarUsageInfoFlags;
+use crate::program_data::{ScopeData, VarUsageInfoFlags};
 
 /// Methods related to option `dead_code`.
 impl Optimizer<'_> {
@@ -48,14 +48,23 @@ impl Optimizer<'_> {
 
             // We only handle identifiers on lhs for now.
             if let Some(lhs) = assign.left.as_ident() {
+                let used_arguments = self
+                    .data
+                    .scopes
+                    .get(&self.ctx.scope)
+                    .map(|s| s.contains(ScopeData::USED_ARGUMENTS))
+                    .unwrap_or(false);
+
                 if self
                     .data
                     .vars
                     .get(&lhs.to_id())
                     .map(|var| {
                         var.flags.contains(
                             VarUsageInfoFlags::DECLARED.union(VarUsageInfoFlags::IS_FN_LOCAL),
-                        ) && !var.flags.contains(VarUsageInfoFlags::DECLARED_AS_FN_PARAM)
+                        ) && !(used_arguments
+                            && var.flags.contains(VarUsageInfoFlags::DECLARED_AS_FN_PARAM))
+                            && !var.flags.intersects(VarUsageInfoFlags::EXPORTED)
                     })
                     .unwrap_or(false)
                 {
@@ -78,15 +87,23 @@ impl Optimizer<'_> {
                 }
 
                 if let Some(lhs) = assign.left.as_ident() {
-                    //
+                    let used_arguments = self
+                        .data
+                        .scopes
+                        .get(&self.ctx.scope)
+                        .map(|s| s.contains(ScopeData::USED_ARGUMENTS))
+                        .unwrap_or(false);
+
                     if self
                         .data
                         .vars
                         .get(&lhs.to_id())
                         .map(|var| {
                             var.flags.contains(
                                 VarUsageInfoFlags::DECLARED.union(VarUsageInfoFlags::IS_FN_LOCAL),
-                            )
+                            ) && !(used_arguments
+                                && var.flags.contains(VarUsageInfoFlags::DECLARED_AS_FN_PARAM))
+                                && !var.flags.contains(VarUsageInfoFlags::EXPORTED)
                         })
                         .unwrap_or(false)
                     {

crates/swc_ecma_minifier/tests/benches-full/echarts.js

@@ -11474,7 +11474,7 @@
                 // check: category-no-encode-has-axis-data in dataset.html
                 var data = series.getData(), isValueMultipleLine = reduce(value, function(isValueMultipleLine, val, idx) {
                     var dimItem = data.getDimensionInfo(idx);
-                    return isValueMultipleLine = isValueMultipleLine || dimItem && !1 !== dimItem.tooltip && null != dimItem.displayName;
+                    return isValueMultipleLine || dimItem && !1 !== dimItem.tooltip && null != dimItem.displayName;
                 }, !1), inlineValues = [], inlineValueTypes = [], blocks = [];
                 function setEachItem(val, dim) {
                     var dimInfo = data.getDimensionInfo(dim); // If `dimInfo.tooltip` is not set, show tooltip.
@@ -18950,7 +18950,7 @@
      */ function(tpl, value, isUTC) {
             deprecateReplaceLog('echarts.format.formatTime', 'echarts.time.format'), ('week' === tpl || 'month' === tpl || 'quarter' === tpl || 'half-year' === tpl || 'year' === tpl) && (tpl = 'MM-dd\nyyyy');
             var date = parseDate(value), utc = isUTC ? 'UTC' : '', y = date['get' + utc + 'FullYear'](), M = date['get' + utc + 'Month']() + 1, d = date['get' + utc + 'Date'](), h = date['get' + utc + 'Hours'](), m = date['get' + utc + 'Minutes'](), s = date['get' + utc + 'Seconds'](), S = date['get' + utc + 'Milliseconds']();
-            return tpl = tpl.replace('MM', pad(M, 2)).replace('M', M).replace('yyyy', y).replace('yy', y % 100 + '').replace('dd', pad(d, 2)).replace('d', d).replace('hh', pad(h, 2)).replace('h', h).replace('mm', pad(m, 2)).replace('m', m).replace('ss', pad(s, 2)).replace('s', s).replace('SSS', pad(S, 3));
+            return tpl.replace('MM', pad(M, 2)).replace('M', M).replace('yyyy', y).replace('yy', y % 100 + '').replace('dd', pad(d, 2)).replace('d', d).replace('hh', pad(h, 2)).replace('h', h).replace('mm', pad(m, 2)).replace('m', m).replace('ss', pad(s, 2)).replace('s', s).replace('SSS', pad(S, 3));
         },
         capitalFirst: /**
      * Capital first

crates/swc_ecma_minifier/tests/benches-full/terser.js

@@ -19779,7 +19779,7 @@
             mangle_options: options.mangle
         }).compress(toplevel)), timings && (timings.scope = Date.now()), options.mangle && toplevel.figure_out_scope(options.mangle), timings && (timings.mangle = Date.now()), options.mangle && (toplevel.compute_char_frequency(options.mangle), toplevel.mangle_names(options.mangle), toplevel = function(ast, options) {
             var cprivate = -1, private_cache = new Map(), nth_identifier = options.nth_identifier || base54;
-            return ast = ast.transform(new TreeTransformer(function(node) {
+            return ast.transform(new TreeTransformer(function(node) {
                 node instanceof AST_ClassPrivateProperty || node instanceof AST_PrivateMethod || node instanceof AST_PrivateGetter || node instanceof AST_PrivateSetter || node instanceof AST_PrivateIn ? node.key.name = mangle_private(node.key.name) : node instanceof AST_DotHash && (node.property = mangle_private(node.property));
             }));
             function mangle_private(name) {

crates/swc_ecma_minifier/tests/benches-full/victory.js

@@ -14507,7 +14507,7 @@
                         "left",
                         "right"
                     ].reduce(function(memo, opt) {
-                        return memo = handles[opt] && _this.withinBounds(point, handles[opt]) ? memo.concat(opt) : memo;
+                        return handles[opt] && _this.withinBounds(point, handles[opt]) ? memo.concat(opt) : memo;
                     }, []);
                     return activeHandles.length && activeHandles;
                 },
@@ -14909,7 +14909,7 @@
                                     "left",
                                     "right"
                                 ].reduce(function(memo, curr) {
-                                    return memo = handleProps[curr] ? memo.concat(react__WEBPACK_IMPORTED_MODULE_3___default.a.cloneElement(handleComponent, lodash_assign__WEBPACK_IMPORTED_MODULE_1___default()({
+                                    return handleProps[curr] ? memo.concat(react__WEBPACK_IMPORTED_MODULE_3___default.a.cloneElement(handleComponent, lodash_assign__WEBPACK_IMPORTED_MODULE_1___default()({
                                         key: "".concat(name, "-handle-").concat(curr)
                                     }, handleProps[curr]))) : memo;
                                 }, []);
@@ -17898,16 +17898,16 @@
                 switch(textAnchor){
                     case "start":
                         return widths.reduce(function(memo, width, i) {
-                            return memo = i < index ? memo + width : memo;
+                            return i < index ? memo + width : memo;
                         }, 0);
                     case "end":
                         return widths.reduce(function(memo, width, i) {
-                            return memo = i > index ? memo - width : memo;
+                            return i > index ? memo - width : memo;
                         }, 0);
                     default:
                         // middle
                         return widths.reduce(function(memo, width, i) {
-                            return memo = i === index ? memo + width / 2 : memo + (i < index ? width : 0);
+                            return i === index ? memo + width / 2 : memo + (i < index ? width : 0);
                         }, -totalWidth / 2);
                 }
             }, getChildBackgrounds = function(calculatedProps, tspanValues) {
@@ -19937,7 +19937,7 @@
                         value: function(props, externalMutations) {
                             if (!lodash_isEmpty__WEBPACK_IMPORTED_MODULE_2___default()(externalMutations)) {
                                 var callbacks = props.externalEventMutations.reduce(function(memo, mutation) {
-                                    return memo = lodash_isFunction__WEBPACK_IMPORTED_MODULE_5___default()(mutation.callback) ? memo.concat(mutation.callback) : memo;
+                                    return lodash_isFunction__WEBPACK_IMPORTED_MODULE_5___default()(mutation.callback) ? memo.concat(mutation.callback) : memo;
                                 }, []), compiledCallbacks = callbacks.length ? function() {
                                     callbacks.forEach(function(c) {
                                         return c();
@@ -21385,7 +21385,7 @@
                         if (!lodash_isEmpty__WEBPACK_IMPORTED_MODULE_7___default()(eventReturn)) {
                             var callbacks = compileCallbacks(eventReturn);
                             _this2.setState(Array.isArray(eventReturn) ? eventReturn.reduce(function(memo, props) {
-                                return memo = lodash_assign__WEBPACK_IMPORTED_MODULE_8___default()({}, memo, parseEvent(props, eventKey));
+                                return lodash_assign__WEBPACK_IMPORTED_MODULE_8___default()({}, memo, parseEvent(props, eventKey));
                             }, {}) : parseEvent(eventReturn, eventKey), callbacks);
                         }
                     }; // Returns the state object with the mutation caused by a given eventReturn
@@ -21509,8 +21509,8 @@
            * i.e. any static `defaultEvents` on `labelComponent` will be returned
            */ getComponentEvents: function(props, components) {
                     var events = Array.isArray(components) && components.reduce(function(memo, componentName) {
-                        var _memo, component = props[componentName], defaultEvents = component && component.type && component.type.defaultEvents, componentEvents = lodash_isFunction__WEBPACK_IMPORTED_MODULE_6___default()(defaultEvents) ? defaultEvents(component.props) : defaultEvents;
-                        return memo = Array.isArray(componentEvents) ? (_memo = memo).concat.apply(_memo, _toConsumableArray(componentEvents)) : memo;
+                        var component = props[componentName], defaultEvents = component && component.type && component.type.defaultEvents, componentEvents = lodash_isFunction__WEBPACK_IMPORTED_MODULE_6___default()(defaultEvents) ? defaultEvents(component.props) : defaultEvents;
+                        return Array.isArray(componentEvents) ? memo.concat.apply(memo, _toConsumableArray(componentEvents)) : memo;
                     }, []);
                     return events && events.length ? events : void 0;
                 },
@@ -31426,7 +31426,7 @@
                 filterDatasets: function(props, datasets, bounds) {
                     var _this = this, filtered = datasets.reduce(function(memo, dataset) {
                         var selectedData = _this.getSelectedData(props, dataset.data, bounds);
-                        return memo = selectedData ? memo.concat({
+                        return selectedData ? memo.concat({
                             childName: dataset.childName,
                             eventKey: selectedData.eventKey,
                             data: selectedData.data
@@ -31850,7 +31850,7 @@
                         value: function(props, externalMutations) {
                             if (!lodash_isEmpty__WEBPACK_IMPORTED_MODULE_3___default()(externalMutations)) {
                                 var callbacks = props.externalEventMutations.reduce(function(memo, mutation) {
-                                    return memo = lodash_isFunction__WEBPACK_IMPORTED_MODULE_5___default()(mutation.callback) ? memo.concat(mutation.callback) : memo;
+                                    return lodash_isFunction__WEBPACK_IMPORTED_MODULE_5___default()(mutation.callback) ? memo.concat(mutation.callback) : memo;
                                 }, []), compiledCallbacks = callbacks.length ? function() {
                                     callbacks.forEach(function(c) {
                                         return c();
@@ -33246,7 +33246,7 @@
                                     }) : [
                                         style
                                     ];
-                                    return memo = memo.concat(styleArray);
+                                    return memo.concat(styleArray);
                                 }, []);
                             }
                         },

crates/swc_ecma_minifier/tests/fixture/issues/10935/input.js

@@ -0,0 +1,2 @@
+export let foo;
+foo = 1;

crates/swc_ecma_minifier/tests/fixture/issues/10935/output.js

@@ -0,0 +1,2 @@
+export let foo;
+foo = 1;

crates/swc_ecma_minifier/tests/fixture/issues/2257/full/output.js

@@ -15065,7 +15065,7 @@
             }, R.updateQueue = b, b.lastEffect = a.next = a) : null === (c = b.lastEffect) ? b.lastEffect = a.next = a : (d = c.next, c.next = a, a.next = d, b.lastEffect = a), a;
         }
         function Sh(a) {
-            return Hh().memoizedState = a = {
+            return Hh().memoizedState = {
                 current: a
             };
         }
@@ -15555,13 +15555,13 @@
                         case 0:
                         case 2:
                         case 15:
-                            return a = Pa(a.type, !1);
+                            return Pa(a.type, !1);
                         case 11:
-                            return a = Pa(a.type.render, !1);
+                            return Pa(a.type.render, !1);
                         case 22:
-                            return a = Pa(a.type._render, !1);
+                            return Pa(a.type._render, !1);
                         case 1:
-                            return a = Pa(a.type, !0);
+                            return Pa(a.type, !0);
                         default:
                             return "";
                     }
@@ -17293,7 +17293,7 @@
                 if ("function" == typeof a.render) throw Error(y(188));
                 throw Error(y(268, Object.keys(a)));
             }
-            return a = null === (a = cc(b)) ? null : a.stateNode;
+            return null === (a = cc(b)) ? null : a.stateNode;
         }, exports.flushSync = function(a, b) {
             var c = X;
             if (0 != (48 & c)) return a(b);

crates/swc_ecma_minifier/tests/fixture/issues/typescript/1/output.js

@@ -686,7 +686,7 @@ var ts, ts1, dynamicImportUMDHelper;
          * @param allowComments Whether to allow comments on the export.
          */ function appendExportStatement(statements, exportName, expression, location, allowComments, liveBinding) {
         var statement;
-        return statements = ts1.append(statements, (statement = ts1.setTextRange(factory.createExpressionStatement(createExportExpression(exportName, expression, /* location */ void 0, liveBinding)), location), ts1.startOnNewLine(statement), allowComments || ts1.setEmitFlags(statement, 1536 /* NoComments */ ), statement));
+        return ts1.append(statements, (statement = ts1.setTextRange(factory.createExpressionStatement(createExportExpression(exportName, expression, /* location */ void 0, liveBinding)), location), ts1.startOnNewLine(statement), allowComments || ts1.setEmitFlags(statement, 1536 /* NoComments */ ), statement));
     }
     function createUnderscoreUnderscoreESModule() {
         var statement;

crates/swc_ecma_minifier/tests/fixture/next/react-pdf-renderer/output.js

@@ -25724,7 +25724,7 @@
                         ];
                     },
                     useRef: function(e) {
-                        return rD().memoizedState = e = {
+                        return rD().memoizedState = {
                             current: e
                         };
                     },