Enable the import/no-cycle ESLint plugin rule

Having cyclical imports is obviously not a good idea, and this ESLint plugin rule can help detect those; please see https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/no-cycle.md

.eslintrc

@@ -37,6 +37,7 @@
     "import/extensions": ["error", "always", { "ignorePackages": true, }],
     "import/first": "error",
     "import/named": "error",
+    "import/no-cycle": "error",
     "import/no-empty-named-blocks": "error",
     "import/no-mutable-exports": "error",
     "import/no-self-import": "error",

src/core/xfa/bind.js

@@ -36,12 +36,10 @@ import {
   $removeChild,
   $setValue,
   $text,
-  XFAAttribute,
-  XFAObjectArray,
-  XmlObject,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { BindItems, Field, Items, SetProperty, Text } from "./template.js";
 import { createDataNode, searchNode } from "./som.js";
+import { XFAAttribute, XFAObjectArray, XmlObject } from "./xfa_object.js";
 import { NamespaceIds } from "./namespaces.js";
 import { warn } from "../../shared/util.js";
 

src/core/xfa/builder.js

@@ -23,12 +23,12 @@ import {
   $onChild,
   $resolvePrototypes,
   $root,
-  XFAObject,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { NamespaceSetUp } from "./setup.js";
 import { Template } from "./template.js";
 import { UnknownNamespace } from "./unknown.js";
 import { warn } from "../../shared/util.js";
+import { XFAObject } from "./xfa_object.js";
 
 class Root extends XFAObject {
   constructor(ids) {

src/core/xfa/config.js

@@ -14,9 +14,8 @@
  */
 
 import { $buildXFAObject, NamespaceIds } from "./namespaces.js";
+import { $content, $finalize } from "./symbol_utils.js";
 import {
-  $content,
-  $finalize,
   ContentObject,
   IntegerObject,
   Option01,

src/core/xfa/data.js

@@ -20,7 +20,7 @@ import {
   $setValue,
   $toString,
   $uid,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 
 class DataHandler {
   constructor(root, data) {

src/core/xfa/datasets.js

@@ -19,10 +19,9 @@ import {
   $namespaceId,
   $nodeName,
   $onChild,
-  XFAObject,
-  XmlObject,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { $buildXFAObject, NamespaceIds } from "./namespaces.js";
+import { XFAObject, XmlObject } from "./xfa_object.js";
 
 const DATASETS_NS_ID = NamespaceIds.datasets.id;
 

src/core/xfa/factory.js

@@ -20,7 +20,7 @@ import {
   $text,
   $toHTML,
   $toPages,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { Binder } from "./bind.js";
 import { DataHandler } from "./data.js";
 import { FontFinder } from "./fonts.js";

src/core/xfa/fonts.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { $globalData } from "./xfa_object.js";
+import { $globalData } from "./symbol_utils.js";
 import { stripQuotes } from "./utils.js";
 import { warn } from "../../shared/util.js";
 

src/core/xfa/html_utils.js

@@ -24,12 +24,12 @@ import {
   $pushGlyphs,
   $text,
   $toStyle,
-  XFAObject,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { createValidAbsoluteUrl, warn } from "../../shared/util.js";
 import { getMeasurement, stripQuotes } from "./utils.js";
 import { selectFont } from "./fonts.js";
 import { TextMeasure } from "./text.js";
+import { XFAObject } from "./xfa_object.js";
 
 function measureToString(m) {
   if (typeof m === "string") {

src/core/xfa/layout.js

@@ -20,7 +20,7 @@ import {
   $getTemplateRoot,
   $isSplittable,
   $isThereMoreWidth,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { measureToString } from "./html_utils.js";
 
 // Subform and ExclGroup have a layout so they share these functions.

src/core/xfa/parser.js

@@ -24,7 +24,7 @@ import {
   $onChild,
   $onText,
   $setId,
-} from "./xfa_object.js";
+} from "./symbol_utils.js";
 import { XMLParserBase, XMLParserErrorCode } from "../xml_parser.js";
 import { Builder } from "./builder.js";
 import { warn } from "../../shared/util.js";

src/core/xfa/som.js

@@ -14,17 +14,11 @@
  */
 
 import {
-  $appendChild,
   $getChildren,
   $getChildrenByClass,
   $getChildrenByName,
   $getParent,
-  $namespaceId,
-  XFAObject,
-  XFAObjectArray,
-  XmlObject,
-} from "./xfa_object.js";
-import { NamespaceIds } from "./namespaces.js";
+} from "./symbol_utils.js";
 import { warn } from "../../shared/util.js";
 
 const namePattern = /^[^.[]+/;
@@ -58,7 +52,6 @@ const shortcuts = new Map([
 ]);
 
 const somCache = new WeakMap();
-const NS_DATASETS = NamespaceIds.datasets.id;
 
 function parseIndex(index) {
   index = index.trim();
@@ -193,7 +186,7 @@ function searchNode(
     const { name, cacheName, operator, index } = parsed[i];
     const nodes = [];
     for (const node of root) {
-      if (!(node instanceof XFAObject)) {
+      if (!node.isXFAObject) {
         continue;
       }
 
@@ -218,7 +211,7 @@ function searchNode(
             break;
           case operators.dotHash:
             children = node[$getChildrenByClass](name);
-            if (children instanceof XFAObjectArray) {
+            if (children.isXFAObjectArray) {
               children = children.children;
             } else {
               children = [children];
@@ -265,20 +258,6 @@ function searchNode(
   return root;
 }
 
-function createNodes(root, path) {
-  let node = null;
-  for (const { name, index } of path) {
-    for (let i = 0, ii = !isFinite(index) ? 0 : index; i <= ii; i++) {
-      const nsId = root[$namespaceId] === NS_DATASETS ? -1 : root[$namespaceId];
-      node = new XmlObject(nsId, name);
-      root[$appendChild](node);
-    }
-
-    root = node;
-  }
-  return node;
-}
-
 function createDataNode(root, container, expr) {
   const parsed = parseExpression(expr);
   if (!parsed) {
@@ -302,7 +281,7 @@ function createDataNode(root, container, expr) {
     const { name, operator, index } = parsed[i];
     if (!isFinite(index)) {
       parsed[i].index = 0;
-      return createNodes(root, parsed.slice(i));
+      return root.createNodes(parsed.slice(i));
     }
 
     let children;
@@ -315,7 +294,7 @@ function createDataNode(root, container, expr) {
         break;
       case operators.dotHash:
         children = root[$getChildrenByClass](name);
-        if (children instanceof XFAObjectArray) {
+        if (children.isXFAObjectArray) {
           children = children.children;
         } else {
           children = [children];
@@ -326,19 +305,19 @@ function createDataNode(root, container, expr) {
     }
 
     if (children.length === 0) {
-      return createNodes(root, parsed.slice(i));
+      return root.createNodes(parsed.slice(i));
     }
 
     if (index < children.length) {
       const child = children[index];
-      if (!(child instanceof XFAObject)) {
+      if (!child.isXFAObject) {
         warn(`XFA - Cannot create a node.`);
         return null;
       }
       root = child;
     } else {
       parsed[i].index = index - children.length;
-      return createNodes(root, parsed.slice(i));
+      return root.createNodes(parsed.slice(i));
     }
   }
   return null;

src/core/xfa/symbol_utils.js

@@ -0,0 +1,156 @@
+/* Copyright 2021 Mozilla Foundation
+ *
+ * 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.
+ */
+
+// We use these symbols to avoid name conflict between tags
+// and properties/methods names.
+const $acceptWhitespace = Symbol();
+const $addHTML = Symbol();
+const $appendChild = Symbol();
+const $childrenToHTML = Symbol();
+const $clean = Symbol();
+const $cleanPage = Symbol();
+const $cleanup = Symbol();
+const $clone = Symbol();
+const $consumed = Symbol();
+const $content = Symbol("content");
+const $data = Symbol("data");
+const $dump = Symbol();
+const $extra = Symbol("extra");
+const $finalize = Symbol();
+const $flushHTML = Symbol();
+const $getAttributeIt = Symbol();
+const $getAttributes = Symbol();
+const $getAvailableSpace = Symbol();
+const $getChildrenByClass = Symbol();
+const $getChildrenByName = Symbol();
+const $getChildrenByNameIt = Symbol();
+const $getDataValue = Symbol();
+const $getExtra = Symbol();
+const $getRealChildrenByNameIt = Symbol();
+const $getChildren = Symbol();
+const $getContainedChildren = Symbol();
+const $getNextPage = Symbol();
+const $getSubformParent = Symbol();
+const $getParent = Symbol();
+const $getTemplateRoot = Symbol();
+const $globalData = Symbol();
+const $hasSettableValue = Symbol();
+const $ids = Symbol();
+const $indexOf = Symbol();
+const $insertAt = Symbol();
+const $isCDATAXml = Symbol();
+const $isBindable = Symbol();
+const $isDataValue = Symbol();
+const $isDescendent = Symbol();
+const $isNsAgnostic = Symbol();
+const $isSplittable = Symbol();
+const $isThereMoreWidth = Symbol();
+const $isTransparent = Symbol();
+const $isUsable = Symbol();
+const $lastAttribute = Symbol();
+const $namespaceId = Symbol("namespaceId");
+const $nodeName = Symbol("nodeName");
+const $nsAttributes = Symbol();
+const $onChild = Symbol();
+const $onChildCheck = Symbol();
+const $onText = Symbol();
+const $pushGlyphs = Symbol();
+const $popPara = Symbol();
+const $pushPara = Symbol();
+const $removeChild = Symbol();
+const $root = Symbol("root");
+const $resolvePrototypes = Symbol();
+const $searchNode = Symbol();
+const $setId = Symbol();
+const $setSetAttributes = Symbol();
+const $setValue = Symbol();
+const $tabIndex = Symbol();
+const $text = Symbol();
+const $toPages = Symbol();
+const $toHTML = Symbol();
+const $toString = Symbol();
+const $toStyle = Symbol();
+const $uid = Symbol("uid");
+
+export {
+  $acceptWhitespace,
+  $addHTML,
+  $appendChild,
+  $childrenToHTML,
+  $clean,
+  $cleanPage,
+  $cleanup,
+  $clone,
+  $consumed,
+  $content,
+  $data,
+  $dump,
+  $extra,
+  $finalize,
+  $flushHTML,
+  $getAttributeIt,
+  $getAttributes,
+  $getAvailableSpace,
+  $getChildren,
+  $getChildrenByClass,
+  $getChildrenByName,
+  $getChildrenByNameIt,
+  $getContainedChildren,
+  $getDataValue,
+  $getExtra,
+  $getNextPage,
+  $getParent,
+  $getRealChildrenByNameIt,
+  $getSubformParent,
+  $getTemplateRoot,
+  $globalData,
+  $hasSettableValue,
+  $ids,
+  $indexOf,
+  $insertAt,
+  $isBindable,
+  $isCDATAXml,
+  $isDataValue,
+  $isDescendent,
+  $isNsAgnostic,
+  $isSplittable,
+  $isThereMoreWidth,
+  $isTransparent,
+  $isUsable,
+  $lastAttribute,
+  $namespaceId,
+  $nodeName,
+  $nsAttributes,
+  $onChild,
+  $onChildCheck,
+  $onText,
+  $popPara,
+  $pushGlyphs,
+  $pushPara,
+  $removeChild,
+  $resolvePrototypes,
+  $root,
+  $searchNode,
+  $setId,
+  $setSetAttributes,
+  $setValue,
+  $tabIndex,
+  $text,
+  $toHTML,
+  $toPages,
+  $toString,
+  $toStyle,
+  $uid,
+};