support ExtendScript parser quirks (#5648)

closes #1144

README.md

@@ -930,6 +930,9 @@ can pass additional arguments that control the code output:
   }
   ```
 
+- `extendscript` (default: `false`) — enable workarounds for Adobe ExtendScript
+  bugs
+
 - `galio` (default: `false`) — enable workarounds for ANT Galio bugs
 
 - `indent_level` (default: `4`) — indent by specified number of spaces or the
@@ -1446,3 +1449,17 @@ To allow for better optimizations, the compiler makes various assumptions:
   // Actual:   TypeError: invalid assignment to const 'f'
   ```
   UglifyJS may modify the input which in turn may suppress those errors.
+- Adobe ExtendScript will give incorrect results with the following:
+  ```javascript
+  alert(true ? "PASS" : false ? "FAIL" : null);
+  // Expected: "PASS"
+  // Actual:   "FAIL"
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.
+- Adobe ExtendScript will give incorrect results with the following:
+  ```javascript
+  alert(42 ? null ? "FAIL" : "PASS" : "FAIL");
+  // Expected: "PASS"
+  // Actual:   SyntaxError: Expected: :
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.

lib/output.js

@@ -55,6 +55,7 @@ function OutputStream(options) {
         beautify         : false,
         braces           : false,
         comments         : false,
+        extendscript     : false,
         galio            : false,
         ie               : false,
         indent_level     : 4,
@@ -700,6 +701,7 @@ function OutputStream(options) {
         if (p instanceof AST_Class) return true;
         // (x++)[y]
         // (typeof x).y
+        // https://github.com/mishoo/UglifyJS/issues/115
         if (p instanceof AST_PropAccess) return p.expression === this;
         // (~x)`foo`
         if (p instanceof AST_Template) return p.tag === this;
@@ -875,7 +877,9 @@ function OutputStream(options) {
         return needs_parens_assign_cond(this, output);
     });
     PARENS(AST_Conditional, function(output) {
-        return needs_parens_assign_cond(this, output);
+        return needs_parens_assign_cond(this, output)
+            // https://github.com/mishoo/UglifyJS/issues/1144
+            || output.option("extendscript") && output.parent() instanceof AST_Conditional;
     });
     PARENS(AST_Yield, function(output) {
         return needs_parens_assign_cond(this, output);

test/compress/conditionals.js

@@ -1176,6 +1176,52 @@ trivial_boolean_ternary_expressions : {
     }
 }
 
+extendscript_1: {
+    beautify = {
+        extendscript: true,
+    }
+    input: {
+        var alert = console.log;
+        function f(a, b) {
+            return a ? b ? "foo" : "bar" : "baz";
+        }
+        alert(f());
+        alert(f(42));
+        alert(f(null, true));
+        alert(f([], {}));
+    }
+    expect_exact: 'var alert=console.log;function f(a,b){return a?(b?"foo":"bar"):"baz"}alert(f());alert(f(42));alert(f(null,true));alert(f([],{}));'
+    expect_stdout: [
+        "baz",
+        "bar",
+        "baz",
+        "foo",
+    ]
+}
+
+extendscript_2: {
+    beautify = {
+        extendscript: true,
+    }
+    input: {
+        var alert = console.log;
+        function f(a, b) {
+            return a ? "foo" : b ? "bar" : "baz";
+        }
+        alert(f());
+        alert(f(42));
+        alert(f(null, true));
+        alert(f([], {}));
+    }
+    expect_exact: 'var alert=console.log;function f(a,b){return a?"foo":(b?"bar":"baz")}alert(f());alert(f(42));alert(f(null,true));alert(f([],{}));'
+    expect_stdout: [
+        "baz",
+        "foo",
+        "bar",
+        "foo",
+    ]
+}
+
 issue_1154: {
     options = {
         booleans: true,