feature: @putout/plugin-remove-unreachable-code: backtracking parents and enhancements (#226)

Author: echo094

packages/plugin-remove-unreachable-code/lib/remove-unreachable-code.js

@@ -17,24 +17,38 @@ module.exports.fix = ({siblings}) => {
     }
 };
 
-module.exports.traverse = ({push}) => ({
-    'ReturnStatement|ThrowStatement'(path) {
-        const siblings = path.getAllNextSiblings();
-        
-        if (!siblings.length)
-            return;
-        
+const processBlock = (push, path, leaf) => {
+    const siblings = path.getAllNextSiblings();
+    
+    if (!siblings.length)
+        return;
+    
+    if (leaf) {
         const [first] = siblings;
 
         if (!path.node.argument && (isBlockStatement(first) || isExpressionStatement(first)))
             return false;
-        
-        if (siblings.find(isFunctionDeclaration))
-            return;
+    }
+    
+    for (const sibling of siblings) {
+        if (isFunctionDeclaration(sibling))
+            continue;
 
         push({
-            path: siblings[0],
-            siblings,
+            path: sibling,
+            siblings: [sibling],
         });
+    }
+};
+
+module.exports.traverse = ({push}) => ({
+    'ReturnStatement|ThrowStatement'(path) {
+        let leaf = true;
+        
+        while (path.parentPath?.isBlockStatement()) {
+            processBlock(push, path, leaf);
+            path = path.parentPath;
+            leaf = false;
+        }
     },
 });

packages/plugin-remove-unreachable-code/test/fixture/backtrack-func.js

@@ -0,0 +1,9 @@
+let x3 = 1;
+function fun3(f) {
+  {
+    let x3 = f + 2;
+    return x3 * 2;
+  }
+  function m() {}
+}
+fun3(x3)

packages/plugin-remove-unreachable-code/test/fixture/backtrack-normal-fix.js

@@ -0,0 +1,10 @@
+let x3 = 1;
+
+function fun3(f) {
+    {
+        let x3 = f + 2;
+        return x3 * 2;
+    }
+}
+
+fun3(x3);

packages/plugin-remove-unreachable-code/test/fixture/backtrack-normal.js

@@ -0,0 +1,11 @@
+let x3 = 1;
+
+function fun3(f) {
+    {
+        let x3 = f + 2;
+        return x3 * 2;
+    }
+    return 3;
+}
+
+fun3(x3);

packages/plugin-remove-unreachable-code/test/fixture/hoist-and-other-fix.js

@@ -0,0 +1,4 @@
+function f() {
+    return x;
+    function m() {}
+}

packages/plugin-remove-unreachable-code/test/fixture/hoist-and-other.js

@@ -0,0 +1,5 @@
+function f() {
+    return x;
+    function m() {}
+    return 1;
+}

packages/plugin-remove-unreachable-code/test/remove-unreachable-code.js

@@ -33,3 +33,18 @@ test('plugin-remove-unreachable-code: no report: return-no-arg', (t) => {
     t.noReport('return-no-arg');
     t.end();
 });
+
+test('plugin-remove-unreachable-code: transform: hoist-and-other', (t) => {
+    t.transform('hoist-and-other');
+    t.end();
+});
+
+test('plugin-remove-unreachable-code: transform: backtrack-normal', (t) => {
+    t.transform('backtrack-normal');
+    t.end();
+});
+
+test('plugin-remove-unreachable-code: no report: backtrack-func', (t) => {
+    t.noReport('backtrack-func');
+    t.end();
+});