support limited ufuzz testing for import (#4707)

.github/workflows/ufuzz.yml

@@ -33,10 +33,11 @@ jobs:
       - name: Install GNU Core Utilities
         if: ${{ startsWith(matrix.os, 'macos') }}
         env:
+          HOMEBREW_NO_BOTTLE_SOURCE_FALLBACK: 1
           HOMEBREW_NO_INSTALL_CLEANUP: 1
         shell: bash
         run: |
-          brew install coreutils
+          while !(brew install coreutils); do echo "'brew install' failed - retrying..."; done
       - name: Perform fuzzing
         shell: bash
         run: |

test/reduce.js

@@ -732,7 +732,7 @@ function run_code(code, toplevel, result_cache, timeout) {
     if (!value) {
         var start = Date.now();
         result_cache[key] = value = {
-            result: sandbox.run_code(sandbox.strip_exports(code), toplevel, timeout),
+            result: sandbox.run_code(sandbox.patch_module_statements(code), toplevel, timeout),
             elapsed: Date.now() - start,
         };
     }

test/sandbox.js

@@ -49,13 +49,27 @@ exports.same_stdout = semver.satisfies(process.version, "0.12") ? function(expec
 } : function(expected, actual) {
     return typeof expected == typeof actual && strip_func_ids(expected) == strip_func_ids(actual);
 };
-exports.strip_exports = function(code) {
+exports.patch_module_statements = function(code) {
-    var count = 0;
+    var count = 0, imports = [];
-    return code.replace(/\bexport(?:\s*\{[^}]*}\s*?(?:$|\n|;)|\s+default\b(?:\s*(\(|\{|class\s*\{|class\s+(?=extends\b)|(?:async\s+)?function\s*(?:\*\s*)?\())?|\b)/g, function(match, header) {
+    code = code.replace(/\bexport(?:\s*\{[^}]*}\s*?(?:$|\n|;)|\s+default\b(?:\s*(\(|\{|class\s*\{|class\s+(?=extends\b)|(?:async\s+)?function\s*(?:\*\s*)?\())?|\b)/g, function(match, header) {
         if (!header) return "";
         if (header.length == 1) return "0, " + header;
         return header.slice(0, -1) + " _" + ++count + header.slice(-1);
+    }).replace(/\bimport\b(?:\s*([^('"]+)\bfrom\b)?\s*(['"]).*?\2(?:$|\n|;)/g, function(match, symbols) {
+        if (symbols) {
+            if (!/^[{*]/.test(symbols)) symbols = "default:" + symbols;
+            symbols = symbols.replace(/[{}]/g, "").trim().replace(/\s*,\s*/g, ",");
+            symbols = symbols.replace(/\*/, '"*"').replace(/\bas\s+(?!$|,|as\s)/g, ":");
+            imports.push([
+                "var {",
+                symbols,
+                "} = new Proxy(Object.create(null), { get(_, value) { return { value }; } });",
+            ].join(""));
+        }
+        return "";
     });
+    imports.push("");
+    return imports.join("\n") + code;
 };
 
 function is_error(result) {

test/ufuzz/index.js

@@ -382,7 +382,7 @@ function strictMode() {
 }
 
 function appendExport(stmtDepth, allowDefault) {
-    if (stmtDepth == 1 && rng(20) == 0) {
+    if (SUPPORT.destructuring && stmtDepth == 1 && rng(20) == 0) {
         if (allowDefault && !export_default && rng(5) == 0) {
             export_default = true;
             return "export default ";
@@ -1009,7 +1009,7 @@ function createStatement(recurmax, canThrow, canBreak, canContinue, cannotReturn
       case STMT_SEMI:
         return use_strict && rng(20) === 0 ? '"use strict";' : ";";
       case STMT_EXPR:
-          if (stmtDepth == 1 && !export_default && rng(20) == 0) {
+          if (SUPPORT.destructuring && stmtDepth == 1 && !export_default && rng(20) == 0) {
               export_default = true;
               return "export default " + createExpression(recurmax, COMMA_OK, stmtDepth, canThrow) + ";";
           }
@@ -1019,7 +1019,26 @@ function createStatement(recurmax, canThrow, canBreak, canContinue, cannotReturn
         // note: default does not _need_ to be last
         return "switch (" + createExpression(recurmax, COMMA_OK, stmtDepth, canThrow) + ") { " + createSwitchParts(recurmax, 4, canThrow, canBreak, canContinue, cannotReturn, stmtDepth) + "}";
       case STMT_VAR:
-        if (SUPPORT.destructuring && rng(20) == 0) {
+        if (SUPPORT.destructuring && stmtDepth == 1 && rng(5) == 0) {
+            unique_vars.push("c");
+            var s = rng(2) ? " " + createVarName(MANDATORY) : "";
+            if (rng(10)) {
+                if (s) s += ",";
+                if (rng(2)) {
+                    s += " * as " + createVarName(MANDATORY);
+                } else {
+                    var names = [];
+                    for (var i = rng(4); --i >= 0;) {
+                        var name = createVarName(MANDATORY);
+                        names.push(rng(2) ? getDotKey() + " as " + name : name);
+                    }
+                    s += " { " + names.join(", ") + " }";
+                }
+            }
+            unique_vars.pop();
+            if (s) s += " from";
+            return "import" + s + ' "path/to/module.js";';
+        } else if (SUPPORT.destructuring && rng(20) == 0) {
             var pairs = createAssignmentPairs(recurmax, stmtDepth, canThrow);
             return appendExport(stmtDepth) + "var " + pairs.names.map(function(name, index) {
                 return index in pairs.values ? name + " = " + pairs.values[index] : name;
@@ -1966,7 +1985,7 @@ if (require.main !== module) {
 }
 
 function run_code(code, toplevel) {
-    return sandbox.run_code(sandbox.strip_exports(code), toplevel);
+    return sandbox.run_code(sandbox.patch_module_statements(code), toplevel);
 }
 
 function writeln(stream, msg) {
@@ -2384,8 +2403,8 @@ for (var round = 1; round <= num_iterations; round++) {
             if (!ok && /\bclass\b/.test(original_code)) {
                 var original_strict = run_code('"use strict";' + original_code, toplevel);
                 var uglify_strict = run_code('"use strict";' + uglify_code, toplevel);
-                if (typeof original_strict != "string" && /strict/.test(original_strict.message)) {
+                if (typeof original_strict != "string") {
-                    ok = typeof uglify_strict != "string" && /strict/.test(uglify_strict.message);
+                    ok = typeof uglify_strict != "string";
                 } else {
                     ok = sandbox.same_stdout(original_strict, uglify_strict);
                 }