fix(component replacer): Use symbol for DO_NOT_REPLACE instead of undefined

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/components/markdown-renderer/markdown-extension/blockquote/blockquote-color-extra-tag-replacer.tsx

@@ -22,22 +22,20 @@ import { Optional } from '@mrdrogdrog/optional'
  */
 export class BlockquoteColorExtraTagReplacer extends ComponentReplacer {
   replace(element: Element): NodeReplacement {
-    if (
+    return Optional.of(element)
-      element.tagName === BlockquoteExtraTagMarkdownExtension.tagName &&
+      .filter(
-      element.attribs?.['data-label'] === 'color' &&
+        (element) =>
-      element.children !== undefined
+          element.tagName === BlockquoteExtraTagMarkdownExtension.tagName && element.attribs?.['data-label'] === 'color'
-    ) {
+      )
-      let index = 0
+      .map((element) => element.children[0])
-      return Optional.ofNullable(element.children[0])
       .filter(isText)
       .map((child) => (child as Text).data)
       .filter((content) => cssColor.test(content))
       .map((color) => (
-          <span className={'blockquote-extra'} key={(index += 1)} style={{ color: color }}>
+        <span className={'blockquote-extra'} key={1} style={{ color: color }}>
           <ForkAwesomeIcon key='icon' className={'mx-1'} icon={'tag'} />
         </span>
       ))
       .orElse(DO_NOT_REPLACE)
   }
-  }
 }

src/components/markdown-renderer/markdown-extension/blockquote/blockquote-extra-tag-replacer.tsx

@@ -23,16 +23,17 @@ import { BlockquoteExtraTagMarkdownExtension } from './blockquote-extra-tag-mark
  */
 export class BlockquoteExtraTagReplacer extends ComponentReplacer {
   replace(element: Element, subNodeTransform: SubNodeTransform): NodeReplacement {
-    if (element.tagName !== BlockquoteExtraTagMarkdownExtension.tagName || !element.attribs) {
+    return Optional.of(element)
-      return DO_NOT_REPLACE
+      .filter(
-    }
+        (element) => element.tagName === BlockquoteExtraTagMarkdownExtension.tagName && element.attribs !== undefined
-
+      )
-    return (
+      .map((element) => (
-      <span className={'blockquote-extra'}>
+        <span className={'blockquote-extra'} key={1}>
           {this.buildIconElement(element)}
           {BlockquoteExtraTagReplacer.transformChildren(element, subNodeTransform)}
         </span>
-    )
+      ))
+      .orElse(DO_NOT_REPLACE)
   }
 
   /**

src/components/markdown-renderer/markdown-extension/csv/csv-replacer.tsx

@@ -1,12 +1,13 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { Element } from 'domhandler'
 import React from 'react'
-import { ComponentReplacer } from '../../replace-components/component-replacer'
+import type { NodeReplacement } from '../../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import { CsvTable } from './csv-table'
 import { CodeBlockComponentReplacer } from '../../replace-components/code-block-component-replacer'
 
@@ -14,10 +15,10 @@ import { CodeBlockComponentReplacer } from '../../replace-components/code-block-
  * Detects code blocks with "csv" as language and renders them as table.
  */
 export class CsvReplacer extends ComponentReplacer {
-  public replace(codeNode: Element): React.ReactElement | undefined {
+  public replace(codeNode: Element): NodeReplacement {
     const code = CodeBlockComponentReplacer.extractTextFromCodeNode(codeNode, 'csv')
     if (!code) {
-      return
+      return DO_NOT_REPLACE
     }
 
     const extraData = codeNode.attribs['data-extra']

src/components/markdown-renderer/markdown-extension/highlighted-fence/highlighted-code-replacer.tsx

@@ -1,12 +1,13 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { Element } from 'domhandler'
 import React from 'react'
-import { ComponentReplacer } from '../../replace-components/component-replacer'
+import type { NodeReplacement } from '../../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import { HighlightedCode } from './highlighted-code'
 
 /**
@@ -21,10 +22,10 @@ export class HighlightedCodeReplacer extends ComponentReplacer {
       : undefined
   }
 
-  public replace(codeNode: Element): React.ReactElement | undefined {
+  public replace(codeNode: Element): NodeReplacement {
     const code = HighlightedCodeReplacer.extractCode(codeNode)
     if (!code) {
-      return
+      return DO_NOT_REPLACE
     }
 
     const language = codeNode.attribs['data-highlight-language']

src/components/markdown-renderer/markdown-extension/iframe-capsule/iframe-capsule-replacer.tsx

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
@@ -16,8 +16,9 @@ import { ClickShield } from '../../replace-components/click-shield/click-shield'
  */
 export class IframeCapsuleReplacer extends ComponentReplacer {
   replace(node: Element, subNodeTransform: SubNodeTransform, nativeRenderer: NativeRenderer): NodeReplacement {
-    if (node.name === 'iframe') {
+    return node.name !== 'iframe' ? (
-      return (
+      DO_NOT_REPLACE
+    ) : (
       <ClickShield
         hoverIcon={'globe'}
         targetDescription={node.attribs.src}
@@ -25,8 +26,5 @@ export class IframeCapsuleReplacer extends ComponentReplacer {
         {nativeRenderer()}
       </ClickShield>
     )
-    } else {
-      return DO_NOT_REPLACE
-    }
   }
 }

src/components/markdown-renderer/markdown-extension/image/proxy-image-replacer.tsx

@@ -1,12 +1,13 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { Element } from 'domhandler'
 import React from 'react'
-import { ComponentReplacer } from '../../replace-components/component-replacer'
+import type { NodeReplacement } from '../../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import { ProxyImageFrame } from './proxy-image-frame'
 
 export type ImageClickHandler = (event: React.MouseEvent<HTMLImageElement, MouseEvent>) => void
@@ -22,9 +23,10 @@ export class ProxyImageReplacer extends ComponentReplacer {
     this.clickHandler = clickHandler
   }
 
-  public replace(node: Element): React.ReactElement | undefined {
+  public replace(node: Element): NodeReplacement {
-    if (node.name === 'img') {
+    return node.name !== 'img' ? (
-      return (
+      DO_NOT_REPLACE
+    ) : (
       <ProxyImageFrame
         id={node.attribs.id}
         className={`${node.attribs.class} cursor-zoom-in`}
@@ -37,5 +39,4 @@ export class ProxyImageReplacer extends ComponentReplacer {
       />
     )
   }
-  }
 }

src/components/markdown-renderer/markdown-extension/katex/katex-replacer.tsx

@@ -7,6 +7,7 @@
 import type { Element } from 'domhandler'
 import { isTag } from 'domhandler'
 import React from 'react'
+import type { NodeReplacement } from '../../replace-components/component-replacer'
 import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import { KatexMarkdownExtension } from './katex-markdown-extension'
 import { Optional } from '@mrdrogdrog/optional'
@@ -17,7 +18,7 @@ const KaTeX = React.lazy(() => import(/* webpackChunkName: "katex" */ './katex-f
  * Detects LaTeX syntax and renders it with KaTeX.
  */
 export class KatexReplacer extends ComponentReplacer {
-  public replace(node: Element): React.ReactElement | undefined {
+  public replace(node: Element): NodeReplacement {
     return this.extractKatexContent(node)
       .map((latexContent) => {
         const isInline = !!node.attribs?.['data-inline']

src/components/markdown-renderer/markdown-extension/linemarker/linemarker-replacer.tsx

@@ -1,18 +1,19 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { Element } from 'domhandler'
-import { ComponentReplacer } from '../../replace-components/component-replacer'
+import type { NodeReplacement } from '../../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import { LinemarkerMarkdownExtension } from './linemarker-markdown-extension'
 
 /**
  * Detects line markers and suppresses them in the resulting DOM.
  */
 export class LinemarkerReplacer extends ComponentReplacer {
-  public replace(codeNode: Element): null | undefined {
+  public replace(codeNode: Element): NodeReplacement {
-    return codeNode.name === LinemarkerMarkdownExtension.tagName ? null : undefined
+    return codeNode.name === LinemarkerMarkdownExtension.tagName ? null : DO_NOT_REPLACE
   }
 }

src/components/markdown-renderer/markdown-extension/link-replacer/jump-anchor-replacer.tsx

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
@@ -22,10 +22,10 @@ export class JumpAnchorReplacer extends ComponentReplacer {
     const jumpId = node.attribs['data-jump-target-id']
     delete node.attribs['data-jump-target-id']
     const replacement = nativeRenderer()
-    if (replacement === null || typeof replacement === 'string') {
+    return replacement === null || typeof replacement === 'string' ? (
-      return replacement
+      replacement
-    } else {
+    ) : (
-      return <JumpAnchor {...(replacement.props as AllHTMLAttributes<HTMLAnchorElement>)} jumpTargetId={jumpId} />
+      <JumpAnchor {...(replacement.props as AllHTMLAttributes<HTMLAnchorElement>)} jumpTargetId={jumpId} />
-    }
+    )
   }
 }

src/components/markdown-renderer/markdown-extension/task-list/task-list-replacer.tsx

@@ -1,13 +1,13 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { Element } from 'domhandler'
-import type { ReactElement } from 'react'
 import React from 'react'
-import { ComponentReplacer } from '../../replace-components/component-replacer'
+import type { NodeReplacement } from '../../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import { TaskListCheckbox } from './task-list-checkbox'
 
 export type TaskCheckedChangeHandler = (lineInMarkdown: number, checked: boolean) => void
@@ -20,23 +20,17 @@ export class TaskListReplacer extends ComponentReplacer {
 
   constructor(onTaskCheckedChange?: TaskCheckedChangeHandler) {
     super()
-    this.onTaskCheckedChange = (lineInMarkdown, checked) => {
+    this.onTaskCheckedChange = (lineInMarkdown, checked) => onTaskCheckedChange?.(lineInMarkdown, checked)
-      if (onTaskCheckedChange === undefined) {
-        return
-      }
-      onTaskCheckedChange(lineInMarkdown, checked)
-    }
   }
 
-  public replace(node: Element): ReactElement | undefined {
+  public replace(node: Element): NodeReplacement {
     if (node.attribs?.class !== 'task-list-item-checkbox') {
-      return
+      return DO_NOT_REPLACE
     }
     const lineInMarkdown = Number(node.attribs['data-line'])
-    if (isNaN(lineInMarkdown)) {
+    return isNaN(lineInMarkdown) ? (
-      return undefined
+      DO_NOT_REPLACE
-    }
+    ) : (
-    return (
       <TaskListCheckbox
         onTaskCheckedChange={this.onTaskCheckedChange}
         checked={node.attribs.checked !== undefined}

src/components/markdown-renderer/markdown-extension/upload-indicating-image-frame/upload-indicating-image-frame-replacer.tsx

@@ -1,11 +1,11 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { NodeReplacement } from '../../replace-components/component-replacer'
-import { ComponentReplacer } from '../../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../../replace-components/component-replacer'
 import type { Element } from 'domhandler'
 import { UploadIndicatingFrame } from './upload-indicating-frame'
 
@@ -16,8 +16,10 @@ const uploadIdRegex = /^upload-(.+)$/
  */
 export class UploadIndicatingImageFrameReplacer extends ComponentReplacer {
   replace(node: Element): NodeReplacement {
-    if (node.name === 'img' && uploadIdRegex.test(node.attribs.src)) {
+    return node.name !== 'img' || !uploadIdRegex.test(node.attribs.src) ? (
-      return <UploadIndicatingFrame width={node.attribs.width} height={node.attribs.height} />
+      DO_NOT_REPLACE
-    }
+    ) : (
+      <UploadIndicatingFrame width={node.attribs.width} height={node.attribs.height} />
+    )
   }
 }

src/components/markdown-renderer/replace-components/code-block-component-replacer.ts

@@ -1,11 +1,11 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import type { ValidReactDomElement } from './component-replacer'
+import type { NodeReplacement } from './component-replacer'
-import { ComponentReplacer } from './component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from './component-replacer'
 import type { FunctionComponent } from 'react'
 import React from 'react'
 import type { Element } from 'domhandler'
@@ -22,9 +22,9 @@ export class CodeBlockComponentReplacer extends ComponentReplacer {
     super()
   }
 
-  replace(node: Element): ValidReactDomElement | undefined {
+  replace(node: Element): NodeReplacement {
     const code = CodeBlockComponentReplacer.extractTextFromCodeNode(node, this.language)
-    return code ? React.createElement(this.component, { code: code }) : undefined
+    return code ? React.createElement(this.component, { code: code }) : DO_NOT_REPLACE
   }
 
   /**

src/components/markdown-renderer/replace-components/component-replacer.ts

@@ -10,13 +10,13 @@ import type { ReactElement } from 'react'
 
 export type ValidReactDomElement = ReactElement | string | null
 
-export type SubNodeTransform = (node: Node, subKey: number | string) => NodeReplacement
+export type SubNodeTransform = (node: Node, subKey: number | string) => ValidReactDomElement
 
 export type NativeRenderer = () => ValidReactDomElement
 
-export const REPLACE_WITH_NOTHING = null
+export const DO_NOT_REPLACE = Symbol()
-export const DO_NOT_REPLACE = undefined
+
-export type NodeReplacement = ValidReactDomElement | typeof REPLACE_WITH_NOTHING | typeof DO_NOT_REPLACE
+export type NodeReplacement = ValidReactDomElement | typeof DO_NOT_REPLACE
 
 /**
  * Base class for all component replacers.
@@ -42,7 +42,7 @@ export abstract class ComponentReplacer {
    * @param subNodeTransform The transformer that should be used.
    * @return The children as react elements.
    */
-  protected static transformChildren(node: Element, subNodeTransform: SubNodeTransform): NodeReplacement[] {
+  protected static transformChildren(node: Element, subNodeTransform: SubNodeTransform): ValidReactDomElement[] {
     return node.children.map((value, index) => subNodeTransform(value, index))
   }
 

src/components/markdown-renderer/replace-components/custom-tag-with-id-component-replacer.ts

@@ -1,11 +1,11 @@
 /*
- * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
 import type { NodeReplacement } from './component-replacer'
-import { ComponentReplacer } from './component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from './component-replacer'
 import type { FunctionComponent } from 'react'
 import React from 'react'
 import type { Element } from 'domhandler'
@@ -24,7 +24,7 @@ export class CustomTagWithIdComponentReplacer extends ComponentReplacer {
 
   public replace(node: Element): NodeReplacement {
     const id = this.extractId(node)
-    return id ? React.createElement(this.component, { id: id }) : undefined
+    return id ? React.createElement(this.component, { id: id }) : DO_NOT_REPLACE
   }
 
   /**

src/components/markdown-renderer/utils/node-to-react-transformer.test.tsx

@@ -8,7 +8,7 @@ import { NodeToReactTransformer } from './node-to-react-transformer'
 import { Element } from 'domhandler'
 import type { ReactElement, ReactHTMLElement } from 'react'
 import type { NodeReplacement } from '../replace-components/component-replacer'
-import { ComponentReplacer, DO_NOT_REPLACE, REPLACE_WITH_NOTHING } from '../replace-components/component-replacer'
+import { ComponentReplacer, DO_NOT_REPLACE } from '../replace-components/component-replacer'
 
 describe('node to react transformer', () => {
   let nodeToReactTransformer: NodeToReactTransformer
@@ -30,7 +30,7 @@ describe('node to react transformer', () => {
       nodeToReactTransformer.setReplacers([
         new (class extends ComponentReplacer {
           replace(): NodeReplacement {
-            return REPLACE_WITH_NOTHING
+            return null
           }
         })()
       ])

src/components/markdown-renderer/utils/node-to-react-transformer.tsx

@@ -8,7 +8,7 @@ import type { Element, Node } from 'domhandler'
 import { isTag } from 'domhandler'
 import { convertNodeToReactElement } from '@hedgedoc/html-to-react/dist/convertNodeToReactElement'
 import type { ComponentReplacer, NodeReplacement, ValidReactDomElement } from '../replace-components/component-replacer'
-import { DO_NOT_REPLACE, REPLACE_WITH_NOTHING } from '../replace-components/component-replacer'
+import { DO_NOT_REPLACE } from '../replace-components/component-replacer'
 import React from 'react'
 import type { LineWithId } from '../markdown-extension/linemarker/types'
 import { Optional } from '@mrdrogdrog/optional'
@@ -45,7 +45,7 @@ export class NodeToReactTransformer {
    * @param index The index of the node within its parents child list.
    * @return the created react element
    */
-  public translateNodeToReactElement(node: Node, index: number | string): ValidReactDomElement | undefined {
+  public translateNodeToReactElement(node: Node, index: number | string): ValidReactDomElement {
     return isTag(node)
       ? this.translateElementToReactElement(node, index)
       : convertNodeToReactElement(node, index, this.translateNodeToReactElement.bind(this))
@@ -58,10 +58,10 @@ export class NodeToReactTransformer {
    * @param index The index of the element within its parents child list.
    * @return the created react element
    */
-  private translateElementToReactElement(element: Element, index: number | string): ValidReactDomElement | undefined {
+  private translateElementToReactElement(element: Element, index: number | string): ValidReactDomElement {
     const elementKey = this.calculateUniqueKey(element).orElseGet(() => (-index).toString())
     const replacement = this.findElementReplacement(element, elementKey)
-    if (replacement === REPLACE_WITH_NOTHING) {
+    if (replacement === null) {
       return null
     } else if (replacement === DO_NOT_REPLACE) {
       return this.renderNativeNode(element, elementKey)
@@ -101,7 +101,7 @@ export class NodeToReactTransformer {
    *
    * @param element The {@link Element} that should be checked.
    * @param elementKey The unique key for the element
-   * @return The replacement or {@link DO_NOT_REPLACE} if the element shouldn't be replaced or {@link REPLACE_WITH_NOTHING} if the node shouldn't be rendered at all.
+   * @return The replacement or {@link DO_NOT_REPLACE} if the element shouldn't be replaced with a custom component.
    */
   private findElementReplacement(element: Element, elementKey: string): NodeReplacement {
     const transformer = this.translateNodeToReactElement.bind(this)