1 files changed, 153 insertions, 0 deletions
diff --git a/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-mixing-eager-and-lazy.js b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-mixing-eager-and-lazy.js
new file mode 100644
index 0000000000..0d158731ea
--- /dev/null
+++ b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-mixing-eager-and-lazy.js
@@ -0,0 +1,153 @@
+/**
+ * @fileoverview Reject use of lazy getters for modules that's loaded early in
+ *               the startup process and not necessarily be lazy.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+"use strict";
+const helpers = require("../helpers");
+
+function isIdentifier(node, id) {
+  return node.type === "Identifier" && node.name === id;
+}
+
+function isString(node) {
+  return node.type === "Literal" && typeof node.value === "string";
+}
+
+function checkMixed(loadedModules, context, node, type, resourceURI) {
+  if (!loadedModules.has(resourceURI)) {
+    loadedModules.set(resourceURI, type);
+  }
+
+  if (loadedModules.get(resourceURI) === type) {
+    return;
+  }
+
+  context.report({
+    node,
+    messageId: "mixedEagerAndLazy",
+    data: { uri: resourceURI },
+  });
+}
+
+module.exports = {
+  meta: {
+    docs: {
+      url:
+        "https://firefox-source-docs.mozilla.org/code-quality/lint/linters/eslint-plugin-mozilla/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-mixed-eager-and-lazy.html",
+    },
+    messages: {
+      mixedEagerAndLazy:
+        'Module "{{uri}}" is loaded eagerly, and should not be used for lazy getter.',
+    },
+    type: "problem",
+  },
+
+  create(context) {
+    const loadedModules = new Map();
+
+    return {
+      ImportDeclaration(node) {
+        const resourceURI = node.source.value;
+        checkMixed(loadedModules, context, node, "eager", resourceURI);
+      },
+      CallExpression(node) {
+        if (node.callee.type !== "MemberExpression") {
+          return;
+        }
+
+        let callerSource;
+        try {
+          callerSource = helpers.getASTSource(node.callee);
+        } catch (e) {
+          return;
+        }
+
+        if (
+          (callerSource === "ChromeUtils.import" ||
+            callerSource === "ChromeUtils.importESModule") &&
+          helpers.getIsTopLevelAndUnconditionallyExecuted(
+            context.getAncestors()
+          )
+        ) {
+          if (node.arguments.length < 1) {
+            return;
+          }
+          const resourceURINode = node.arguments[0];
+          if (!isString(resourceURINode)) {
+            return;
+          }
+          checkMixed(
+            loadedModules,
+            context,
+            node,
+            "eager",
+            resourceURINode.value
+          );
+        }
+
+        if (
+          callerSource === "XPCOMUtils.defineLazyModuleGetter" ||
+          callerSource === "ChromeUtils.defineModuleGetter"
+        ) {
+          if (node.arguments.length < 3) {
+            return;
+          }
+          if (!isIdentifier(node.arguments[0], "lazy")) {
+            return;
+          }
+
+          const resourceURINode = node.arguments[2];
+          if (!isString(resourceURINode)) {
+            return;
+          }
+          checkMixed(
+            loadedModules,
+            context,
+            node,
+            "lazy",
+            resourceURINode.value
+          );
+        } else if (
+          callerSource === "XPCOMUtils.defineLazyModuleGetters" ||
+          callerSource === "ChromeUtils.defineESModuleGetters"
+        ) {
+          if (node.arguments.length < 2) {
+            return;
+          }
+          if (!isIdentifier(node.arguments[0], "lazy")) {
+            return;
+          }
+
+          const obj = node.arguments[1];
+          if (obj.type !== "ObjectExpression") {
+            return;
+          }
+          for (let prop of obj.properties) {
+            if (prop.type !== "Property") {
+              continue;
+            }
+            if (prop.kind !== "init") {
+              continue;
+            }
+            const resourceURINode = prop.value;
+            if (!isString(resourceURINode)) {
+              continue;
+            }
+            checkMixed(
+              loadedModules,
+              context,
+              node,
+              "lazy",
+              resourceURINode.value
+            );
+          }
+        }
+      },
+    };
+  },
+};