🚀 Flatten Literals in TemplateLiterals

build-system/babel-plugins/babel-plugin-transform-templates/index.js

@@ -0,0 +1,73 @@
+/**
+ * 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.
+ */
+
+module.exports = function ({types: t}) {
+  function whichCloneQuasi(clonedQuasis, index) {
+    for (let i = index; i >= 0; i--) {
+      const quasi = clonedQuasis[i];
+      if (quasi !== null) {
+        return index;
+      }
+    }
+  }
+
+  return {
+    name: 'flatten-template-literals',
+    visitor: {
+      TemplateLiteral(path) {
+        const {expressions, quasis} = path.node;
+        let newQuasis = [...quasis.map((quasi) => t.cloneNode(quasi))];
+        let newExpressions = [
+          ...expressions.map((expression) => t.cloneNode(expression)),
+        ];
+        let conversions = 0;
+
+        for (let index = expressions.length; index >= 0; index--) {
+          const expression = expressions[index];
+          if (
+            t.isStringLiteral(expression) ||
+            t.isNumericLiteral(expression) ||
+            t.isBooleanLiteral(expression)
+          ) {
+            const {value} = expression;
+            const readIndex = whichCloneQuasi(newQuasis, index + 1);
+            const modifyIndex = whichCloneQuasi(newQuasis, index);
+            const {value: changedValue} = newQuasis[readIndex];
+            const {value: previousValue} = newQuasis[modifyIndex];
+
+            newQuasis[modifyIndex] = t.templateElement({
+              raw: previousValue.raw + value + changedValue.raw,
+              cooked: previousValue.cooked + value + changedValue.cooked,
+            });
+            newQuasis[index + 1] = null;
+            newExpressions[index] = null;
+            conversions++;
+          }
+        }
+
+        if (conversions === 0) {
+          return;
+        }
+
+        newQuasis = newQuasis.filter(Boolean);
+        newExpressions = newExpressions.filter(Boolean);
+
+        path.replaceWith(t.templateLiteral(newQuasis, newExpressions));
+        path.skip();
+      },
+    },
+  };
+};

build-system/babel-plugins/babel-plugin-transform-templates/test/fixtures/transform/literals/input.js

@@ -0,0 +1,24 @@
+/**
+ * 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.
+ */
+
+let none = `/rtv/100/log-messages.simple.json`;
+let start = `${'123'}/foo`;
+let middle = `/rtv/${'012003312116250'}/log-messages.simple.json`;
+let end = `rtv/${'123'}`;
+
+
+let number = `${123}/foo`;
+let boolean = `${true}/foo`;

build-system/babel-plugins/babel-plugin-transform-templates/test/fixtures/transform/literals/options.json

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

build-system/babel-plugins/babel-plugin-transform-templates/test/fixtures/transform/literals/output.js

@@ -0,0 +1,21 @@
+/**
+ * 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.
+ */
+let none = `/rtv/100/log-messages.simple.json`;
+let start = `123/foo`;
+let middle = `/rtv/012003312116250/log-messages.simple.json`;
+let end = `rtv/123`;
+let number = `123/foo`;
+let boolean = `true/foo`;

build-system/babel-plugins/babel-plugin-transform-templates/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);

build-system/compile/build.conf.js

@@ -46,6 +46,7 @@ const postCompilationPlugins = (isEsmBuild) =>
     ? [
         localPlugin('transform-minified-comments'),
         localPlugin('transform-function-declarations'),
+        localPlugin('transform-templates'),
       ]
     : [];