🚀 Transformer for removing AMP devAssert, working on existing known cases

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/index.js

@@ -0,0 +1,165 @@
+/**
+ * Copyright 2020 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Is a MemberExpression "thenable", `foo().then(() => {});`
+ *
+ * @param {babel.MemberExpression} memberExpression
+ * @return {boolean}
+ */
+function isThenable(memberExpression) {
+  return memberExpression.get('property').isIdentifier({name: 'then'});
+}
+
+/**
+ * Does a MemberExpression have a inner CallExpression? Return it.
+ *
+ * @param {babel.MemberExpression} memberExpression
+ * @return {undefined | babel.CallExpression}
+ */
+function getMatchingInnerCallExpression(memberExpression) {
+  const memberObject = memberExpression.get('object');
+
+  if (
+    memberObject.isCallExpression() &&
+    memberObject.get('callee').isIdentifier({name: 'devAssert'})
+  ) {
+    return memberObject;
+  }
+
+  return undefined;
+}
+
+/**
+ * Extend babel's path.evaluate with extra confidence for very specific scenarios in this transform.
+ *
+ * @param {babel.CallExpression} callExpression
+ * @return {babel.Evaluation}
+ */
+function evaluateDevAssert(callExpression) {
+  const argument = callExpression.get('arguments.0');
+  if (argument.isMemberExpression()) {
+    return {confident: true};
+  }
+  if (argument.isStringLiteral()) {
+    return {confident: true, value: argument.node.value};
+  }
+
+  return argument.evaluate();
+}
+
+module.exports = function ({types: t}) {
+  /**
+   * Given a potentially literal value, attempt to create a babel AST Literal Node for it.
+   *
+   * @param {*} value to try and create a babel literal for.
+   * @return {undefined | babel.NumericLiteral | babel.StringLiteral | babel.BooleanLiteral} value
+   */
+  function usableEvaluateValue(value) {
+    switch (typeof value) {
+      case 'number':
+        return t.numericLiteral(value);
+      case 'string':
+        return t.stringLiteral(value);
+      case 'boolean':
+        return t.booleanLiteral(value);
+      case 'object':
+        if (String(value) === 'null') {
+          return t.nullLiteral();
+        }
+        return undefined;
+      default:
+        return undefined;
+    }
+  }
+
+  /**
+   * Given a wrapping CallExpression and inner MemberExpression.
+   * Attempt to find and replace the contents of a CallExpression inside the MemberExpression.
+   *
+   * @param {babel.CallExpression} callExpression
+   * @param {babel.MemberExpression} memberExpression
+   * @return {boolean}
+   */
+  function handleInnerMemberExpression(callExpression, memberExpression) {
+    const innerCallExpression = getMatchingInnerCallExpression(
+      memberExpression
+    );
+    if (innerCallExpression) {
+      const evalutedDevAssert = evaluateDevAssert(innerCallExpression);
+      if (!evalutedDevAssert.confident) {
+        return;
+      }
+
+      // MemberExpression has an inner CallExpression with a removable `devAssert`.
+      if (isThenable(memberExpression)) {
+        // MemberExpression is thenable, so removing the `devAssert` means thenabling the first argument of `devAssert`.
+        const newCallee = innerCallExpression.get('arguments.0');
+        const newArguments = callExpression.get('arguments');
+        const newCallExpression = t.callExpression(
+          t.cloneDeep(newCallee.node),
+          [...newArguments.map((arg) => t.cloneDeep(arg.node))]
+        );
+
+        callExpression.replaceWith(newCallExpression);
+        return true;
+      }
+
+      return false;
+    }
+
+    return true;
+  }
+
+  return {
+    visitor: {
+      CallExpression(path) {
+        const callee = path.get('callee');
+
+        if (callee.isMemberExpression()) {
+          handleInnerMemberExpression(path, callee);
+          return;
+        }
+
+        if (callee.isIdentifier({name: 'devAssert'})) {
+          const evaluatedDevAssert = evaluateDevAssert(path);
+
+          if (
+            evaluatedDevAssert.confident &&
+            evaluatedDevAssert.value !== undefined
+          ) {
+            const replacement = usableEvaluateValue(evaluatedDevAssert.value);
+            if (replacement !== undefined) {
+              if (t.isExpressionStatement(path.parent)) {
+                // When the direct parent of a `devAssert` is a ExpressionStatement, it can safely be removed.
+                // This is only true when the replacement was statically analyseable.
+                path.remove();
+                return;
+              }
+
+              // Given the replacement can be statically analysed, replace the value with the static replacement.
+              path.replaceWith(replacement);
+              return;
+            }
+          }
+
+          // In other conditions, simply remove the `devAssert()` wrapper and allow the first argument to exist.
+          path.replaceWith(path.get('arguments.0'));
+        }
+      },
+    },
+  };
+};

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/fixtures/transform-assertions/invoked/input.js

@@ -0,0 +1,22 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+devAssert(1 + 1);
+devAssert('');
+devAssert(false);
+devAssert(null);
+devAssert(0);
+devAssert(dev().assert(2 + 2));
+let result = devAssert(foo, 'hello', 'world');

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/fixtures/transform-assertions/invoked/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../.."]
+}

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/fixtures/transform-assertions/invoked/output.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright 2019 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+dev().assert(2 + 2);
+let result = foo;

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/fixtures/transform-assertions/thenable/input.js

@@ -0,0 +1,33 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class ThenableSuccess {
+  refresh() {
+    return devAssert(this.promise_).then(() => {
+      console.log('success');
+    });
+  }
+}
+
+class ThenableSuccessFailure {
+  refresh() {
+    return devAssert(this.promise_).then(() => {
+      console.log('success');
+    }, () => {
+      console.log('failure');
+    });
+  }
+}

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/fixtures/transform-assertions/thenable/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../.."]
+}

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/fixtures/transform-assertions/thenable/output.js

@@ -0,0 +1,34 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+class ThenableSuccess {
+  refresh() {
+    return this.promise_(() => {
+      console.log('success');
+    });
+  }
+
+}
+
+class ThenableSuccessFailure {
+  refresh() {
+    return this.promise_(() => {
+      console.log('success');
+    }, () => {
+      console.log('failure');
+    });
+  }
+
+}

build-system/babel-plugins/babel-plugin-amp-dev-assert-transformer/test/index.js

@@ -0,0 +1,19 @@
+/**
+ * Copyright 2020 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const runner = require('@babel/helper-plugin-test-runner').default;
+
+runner(__dirname);