Fix style being missed on patchDocument

There were scenarios in which patching a document would result in loss
of style for the template runs and, possibly, their right-adjacent run
as well (post-splitting). That was due to the run style elements not
being added to the newly created runs.

This commit addresses this issue by introducing a new, optional, flag
for the `patchDocument` function: `keepOriginalStyles`. It defaults to
`false` (current behavior) and, when `true`, ensures that there is no
loss of styling.

This should address https://github.com/dolanmiu/docx/issues/2293.

src/patcher/from-docx.ts

@@ -49,6 +49,7 @@ export type IPatch = ParagraphPatch | FilePatch;
 
 export interface PatchDocumentOptions {
     readonly patches: { readonly [key: string]: IPatch };
+    readonly keepOriginalStyles?: boolean;
 }
 
 const imageReplacer = new ImageReplacer();
@@ -128,6 +129,7 @@ export const patchDocument = async (data: InputDataType, options: PatchDocumentO
                     patchText,
                     renderedParagraphs,
                     context,
+                    options.keepOriginalStyles,
                 );
             }
 

src/patcher/replacer.spec.ts

@@ -44,6 +44,28 @@ const MOCK_JSON = {
                         },
                     ],
                 },
+                {
+                    type: "element",
+                    name: "w:p",
+                    elements: [
+                        {
+                            type: "element",
+                            name: "w:r",
+                            elements: [
+                                {
+                                    type: "element",
+                                    name: "w:rPr",
+                                    elements: [{ type: "element", name: "w:b", attributes: { "w:val": "1" } }],
+                                },
+                                {
+                                    type: "element",
+                                    name: "w:t",
+                                    elements: [{ type: "text", text: "What a {{bold}} text!" }],
+                                },
+                            ],
+                        },
+                    ],
+                },
             ],
         },
     ],
@@ -115,6 +137,93 @@ describe("replacer", () => {
             expect(JSON.stringify(output)).to.contain("Delightful Header");
         });
 
+        it("should replace paragraph type keeping original styling if keepOriginalStyles is true", () => {
+            const output = replacer(
+                MOCK_JSON,
+                {
+                    type: PatchType.PARAGRAPH,
+                    children: [new TextRun("sweet")],
+                },
+                "{{bold}}",
+                [
+                    {
+                        text: "What a {{bold}} text!",
+                        runs: [
+                            {
+                                text: "What a {{bold}} text!",
+                                parts: [{ text: "What a {{bold}} text!", index: 1, start: 0, end: 21 }],
+                                index: 0,
+                                start: 0,
+                                end: 21,
+                            },
+                        ],
+                        index: 0,
+                        path: [0, 0, 1],
+                    },
+                ],
+                {
+                    file: {} as unknown as File,
+                    viewWrapper: {
+                        Relationships: {},
+                    } as unknown as IViewWrapper,
+                    stack: [],
+                },
+                true,
+            );
+
+            expect(JSON.stringify(output)).to.contain("sweet");
+            expect(output.elements![0].elements![1].elements).toMatchObject([
+                {
+                    type: "element",
+                    name: "w:r",
+                    elements: [
+                        {
+                            type: "element",
+                            name: "w:rPr",
+                            elements: [{ type: "element", name: "w:b", attributes: { "w:val": "1" } }],
+                        },
+                        {
+                            type: "element",
+                            name: "w:t",
+                            elements: [{ type: "text", text: "What a " }],
+                        },
+                    ],
+                },
+                {
+                    type: "element",
+                    name: "w:r",
+                    elements: [
+                        {
+                            type: "element",
+                            name: "w:rPr",
+                            elements: [{ type: "element", name: "w:b", attributes: { "w:val": "1" } }],
+                        },
+                        {
+                            type: "element",
+                            name: "w:t",
+                            elements: [{ type: "text", text: "sweet" }],
+                        },
+                    ],
+                },
+                {
+                    type: "element",
+                    name: "w:r",
+                    elements: [
+                        {
+                            type: "element",
+                            name: "w:rPr",
+                            elements: [{ type: "element", name: "w:b", attributes: { "w:val": "1" } }],
+                        },
+                        {
+                            type: "element",
+                            name: "w:t",
+                            elements: [{ type: "text", text: " text!" }],
+                        },
+                    ],
+                },
+            ]);
+        });
+
         it("should replace document type", () => {
             const output = replacer(
                 MOCK_JSON,

src/patcher/replacer.ts

@@ -20,6 +20,7 @@ export const replacer = (
     patchText: string,
     renderedParagraphs: readonly IRenderedParagraphNode[],
     context: IContext,
+    keepOriginalStyles: boolean = false,
 ): Element => {
     for (const renderedParagraph of renderedParagraphs) {
         const textJson = patch.children
@@ -47,9 +48,29 @@ export const replacer = (
 
                 const index = findRunElementIndexWithToken(paragraphElement, SPLIT_TOKEN);
 
-                const { left, right } = splitRunElement(paragraphElement.elements![index], SPLIT_TOKEN);
+                const runElementToBeReplaced = paragraphElement.elements![index];
+                const { left, right } = splitRunElement(runElementToBeReplaced, SPLIT_TOKEN);
+
+                let newRunElements = textJson;
+                let patchedRightElement = right;
+
+                if (keepOriginalStyles) {
+                    const runElementNonTextualElements =
+                        runElementToBeReplaced.elements?.filter((e) => e.type === "element" && e.name !== "w:t") ?? [];
+
+                    newRunElements = textJson.map((e) => ({
+                        ...e,
+                        elements: [...runElementNonTextualElements, ...(e.elements ?? [])],
+                    }));
+
+                    patchedRightElement = {
+                        ...right,
+                        elements: [...runElementNonTextualElements, ...(right.elements ?? [])],
+                    };
+                }
+
                 // eslint-disable-next-line functional/immutable-data
-                paragraphElement.elements!.splice(index, 1, left, ...textJson, right);
+                paragraphElement.elements!.splice(index, 1, left, ...newRunElements, patchedRightElement);
                 break;
             }
         }