fix terser#510: inline identity functions

michens · Nov 15, 2019 · c1ab100 · c1ab100
1 parent 6589965
commit c1ab100
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Showing 5 changed files with 80 additions and 14 deletions.
diff --git a/lib/compress/index.js b/lib/compress/index.js
@@ -5214,6 +5214,19 @@ def_optimize(AST_Call, function(self, compressor) {
             var args = self.args.concat(value);
             return make_sequence(self, args).optimize(compressor);
         }
+
+        // optimize identity function
+        if (
+            fn.argnames.length === 1
+            && value.start.type === "name"
+            && value.name === fn.argnames[0].name
+        ) {
+            // replace call with first argument or undefined if none passed
+            return make_sequence(
+                self,
+                [self.args[0] || make_node(AST_Undefined)]
+            ).optimize(compressor);
+        }
     }
     if (can_inline) {
         var scope, in_loop, level = -1;

diff --git a/test/compress/async.js b/test/compress/async.js
@@ -165,9 +165,8 @@ async_inline: {
         !async function(){await 3}();
         !async function(x){await console.log(4)}();
 
-        function echo(x){return x}
-        echo(async function(){return await 1}());
-        echo(async function(x){await console.log(2)}());
+        !async function(){await 1}();
+        !async function(x){await console.log(2)}();
 
         console.log("top");
 

diff --git a/test/compress/functions.js b/test/compress/functions.js
@@ -409,11 +409,7 @@ inner_ref: {
         }(2));
     }
     expect: {
-        console.log(function(a) {
-            return a;
-        }(1), function(a) {
-            return a;
-        }());
+        console.log(1, void 0);
     }
     expect_stdout: "1 undefined"
 }
@@ -2107,8 +2103,7 @@ duplicate_arg_var: {
         }("PASS"));
     }
     expect: {
-        console.log((b = "PASS", b));
-        var b;
+        console.log("PASS");
     }
     expect_stdout: "PASS"
 }

diff --git a/test/compress/identity.js b/test/compress/identity.js
@@ -0,0 +1,61 @@
+inline_identity: {
+    options = {
+        defaults: true,
+        toplevel: true
+    }
+    input: {
+        const id = x => x;
+        console.log(id(1), id(2));
+    }
+    expect: {
+        console.log(1, 2);
+    }
+    expect_stdout: "1 2"
+}
+
+inline_identity_no_params: {
+    options = {
+        defaults: true,
+        toplevel: true
+    }
+    input: {
+        const id = x => x;
+        console.log(id(), id());
+    }
+    expect: {
+        console.log(void 0, void 0);
+    }
+    expect_stdout: "undefined undefined"
+}
+
+inline_identity_extra_params: {
+    options = {
+        defaults: true,
+        toplevel: true
+    }
+    input: {
+        const id = x => x;
+        console.log(id(1, 2), id(3, 4));
+    }
+    expect: {
+        console.log(1, 3);
+    }
+    expect_stdout: "1 3"
+}
+
+inline_identity_higher_order: {
+    options = {
+        defaults: true,
+        toplevel: true
+    }
+    input: {
+        const id = x => x;
+        const inc = x => x + 1;
+        console.log(id(inc)(1), id(inc)(2));
+    }
+    expect: {
+        const inc = x => x + 1;
+        console.log(inc(1), inc(2));
+    }
+    expect_stdout: "2 3"
+}
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
@@ -1429,6 +1429,7 @@ defun_inline_3: {
 
 defun_call: {
     options = {
+        evaluate: true,
         inline: true,
         reduce_funcs: true,
         reduce_vars: true,
@@ -1447,10 +1448,7 @@ defun_call: {
     }
     expect: {
         function f() {
-            return 4 + h(1) - h(4);
-            function h(a) {
-                return a;
-            }
+            return 1;
         }
     }
 }