implement compress defaults option

README.md

@@ -613,6 +613,10 @@ If you're using the `X-SourceMap` header instead, you can just omit `sourceMap.u
 
 - `dead_code` (default: `true`) -- remove unreachable code
 
+- `defaults` (default: `true`) -- Pass `false` to disable most default
+  enabled `compress` transforms. Useful when you only want to enable a few
+  `compress` options while disabling the rest.
+
 - `drop_console` (default: `false`) -- Pass `true` to discard calls to
   `console.*` functions. If you wish to drop a specific function call
   such as `console.info` and/or retain side effects from function arguments

lib/compress.js

@@ -47,12 +47,14 @@ function Compressor(options, false_by_default) {
     if (!(this instanceof Compressor))
         return new Compressor(options, false_by_default);
     TreeTransformer.call(this, this.before, this.after);
+    if (options.defaults !== undefined && !options.defaults) false_by_default = true;
     this.options = defaults(options, {
         booleans      : !false_by_default,
         collapse_vars : !false_by_default,
         comparisons   : !false_by_default,
         conditionals  : !false_by_default,
         dead_code     : !false_by_default,
+        defaults      : true,
         drop_console  : false,
         drop_debugger : !false_by_default,
         evaluate      : !false_by_default,

test/compress/defaults.js

@@ -0,0 +1,96 @@
+defaults_undefined: {
+    options = {
+        defaults: undefined,
+    }
+    input: {
+        if (true) {
+            console.log(1 + 2);
+        }
+    }
+    expect: {
+        if (true)
+            console.log(1 + 2);
+    }
+    expect_stdout: "3"
+}
+
+defaults_false: {
+    options = {
+        defaults: false,
+    }
+    input: {
+        if (true) {
+            console.log(1 + 2);
+        }
+    }
+    expect: {
+        if (true)
+            console.log(1 + 2);
+    }
+    expect_stdout: "3"
+}
+
+defaults_false_evaluate_true: {
+    options = {
+        defaults: false,
+        evaluate: true,
+    }
+    input: {
+        if (true) {
+            console.log(1 + 2);
+        }
+    }
+    expect: {
+        if (true)
+            console.log(3);
+    }
+    expect_stdout: "3"
+}
+
+defaults_true: {
+    options = {
+        defaults: true,
+    }
+    input: {
+        if (true) {
+            console.log(1 + 2);
+        }
+    }
+    expect: {
+        console.log(3);
+    }
+    expect_stdout: "3"
+}
+
+defaults_true_conditionals_false: {
+    options = {
+        defaults: true,
+        conditionals: false,
+    }
+    input: {
+        if (true) {
+            console.log(1 + 2);
+        }
+    }
+    expect: {
+        if (1)
+            console.log(3);
+    }
+    expect_stdout: "3"
+}
+
+defaults_true_evaluate_false: {
+    options = {
+        defaults: true,
+        evaluate: false,
+    }
+    input: {
+        if (true) {
+            console.log(1 + 2);
+        }
+    }
+    expect: {
+        1 && console.log(1 + 2);
+    }
+    expect_stdout: "3"
+}

test/input/defaults/input.js

@@ -0,0 +1,3 @@
+if (true) {
+    console.log(1 + 2);
+}

test/mocha/cli.js

@@ -682,4 +682,12 @@ describe("bin/uglifyjs", function () {
             done();
         });
     });
+    it("Should work with -c defaults=false,conditionals", function(done) {
+        var command = uglifyjscmd + " test/input/defaults/input.js -c defaults=false,conditionals";
+        exec(command, function(err, stdout, stderr) {
+            if (err) throw err;
+            assert.strictEqual(stdout, 'true&&console.log(1+2);\n');
+            done();
+        });
+    });
 });

test/mocha/minify.js

@@ -387,4 +387,25 @@ describe("minify", function() {
             }
         });
     });
+
+    it("should work with compress defaults disabled", function() {
+        var code = 'if (true) { console.log(1 + 2); }';
+        var options = {
+            compress: {
+                defaults: false,
+            }
+        };
+        assert.strictEqual(Uglify.minify(code, options).code, 'if(true)console.log(1+2);');
+    });
+
+    it("should work with compress defaults disabled and evaluate enabled", function() {
+        var code = 'if (true) { console.log(1 + 2); }';
+        var options = {
+            compress: {
+                defaults: false,
+                evaluate: true,
+            }
+        };
+        assert.strictEqual(Uglify.minify(code, options).code, 'if(true)console.log(3);');
+    });
 });

test/run-tests.js

@@ -131,7 +131,7 @@ function run_compress_tests() {
                 input.figure_out_scope(test.mangle);
                 input.expand_names(test.mangle);
             }
-            var cmp = new U.Compressor(options, true);
+            var cmp = new U.Compressor(options, options.defaults === undefined ? true : !options.defaults);
             var output = cmp.compress(input);
             output.figure_out_scope(test.mangle);
             if (test.mangle) {