fix(docs): respect custom README content when writing to a custom path

On the `docs-readme` output target it's possible to set a custom output
location with the `.dir` property and the README files generation for
components will then be output to relative paths (like
`my-component/readme.md`) within that directory.

This fixes a bug where that behavior didn't properly respect any
manually-entered content in those readme files, so that if, for
instance, you set the output to `custom-readme-output` and had `"My
Custom Text"` at the top of
`custom-readme-output/components/my-component/readme.md` then running a
build would overwrite your custom text.

This changes things so that we read the content of the custom readme and
use that as the basis for the new text that we're going to write to
disk. This has the effect of preserving the custom text that a user
might have input.

fixes #5400

src/compiler/docs/generate-doc-data.ts

@@ -377,7 +377,10 @@ export const getNameText = (name: string, tags: d.JsonDocsTag[]) => {
  * @returns the user generated content that occurs before {@link AUTO_GENERATE_COMMENT}. If no user generated content
  * exists, or if there was an issue reading the file, return `undefined`
  */
-const getUserReadmeContent = async (compilerCtx: d.CompilerCtx, readmePath: string): Promise<string | undefined> => {
+export const getUserReadmeContent = async (
+  compilerCtx: d.CompilerCtx,
+  readmePath: string,
+): Promise<string | undefined> => {
   try {
     const existingContent = await compilerCtx.fs.readFile(readmePath);
     // subtract one to get everything up to, but not including the auto generated comment

src/compiler/docs/readme/output-docs.ts

@@ -2,6 +2,7 @@ import { join, relative } from '@utils';
 
 import type * as d from '../../../declarations';
 import { AUTO_GENERATE_COMMENT } from '../constants';
+import { getUserReadmeContent } from '../generate-doc-data';
 import { stylesToMarkdown } from './markdown-css-props';
 import { depsToMarkdown } from './markdown-dependencies';
 import { eventsToMarkdown } from './markdown-events';
@@ -12,6 +13,23 @@ import { propsToMarkdown } from './markdown-props';
 import { slotsToMarkdown } from './markdown-slots';
 import { usageToMarkdown } from './markdown-usage';
 
+/**
+ * Generate a README for a given component and write it to disk.
+ *
+ * Typically the README is going to be a 'sibling' to the component's source
+ * code (i.e. written to the same directory) but the user may also configure a
+ * custom output directory by setting {@link d.OutputTargetDocsReadme.dir}.
+ *
+ * Output readme files also include {@link AUTO_GENERATE_COMMENT}, and any
+ * text located _above_ that comment is preserved when the new readme is written
+ * to disk.
+ *
+ * @param config a validated Stencil config
+ * @param compilerCtx the current compiler context
+ * @param readmeOutputs docs-readme output targets
+ * @param docsData documentation data for the component of interest
+ * @param cmps metadata for all the components in the project
+ */
 export const generateReadme = async (
   config: d.ValidatedConfig,
   compilerCtx: d.CompilerCtx,
@@ -25,10 +43,20 @@ export const generateReadme = async (
   await Promise.all(
     readmeOutputs.map(async (readmeOutput) => {
       if (readmeOutput.dir) {
-        const readmeContent = generateMarkdown(userContent, docsData, cmps, readmeOutput);
-        const relPath = relative(config.srcDir, docsData.readmePath);
-        const absPath = join(readmeOutput.dir, relPath);
-        const results = await compilerCtx.fs.writeFile(absPath, readmeContent);
+        const relativeReadmePath = relative(config.srcDir, docsData.readmePath);
+        const readmeOutputPath = join(readmeOutput.dir, relativeReadmePath);
+
+        const currentReadmeContent =
+          readmeOutput.dir !== config.srcDir
+            ? // The user set a custom `.dir` property, which is where we're going
+              // to write the updated README. We need to read the non-automatically
+              // generated content from that file and preserve that.
+              await getUserReadmeContent(compilerCtx, readmeOutputPath)
+            : userContent;
+
+        const readmeContent = generateMarkdown(currentReadmeContent, docsData, cmps, readmeOutput);
+
+        const results = await compilerCtx.fs.writeFile(readmeOutputPath, readmeContent);
         if (results.changedContent) {
           if (isUpdate) {
             config.logger.info(`updated readme docs: ${docsData.tag}`);
@@ -42,15 +70,15 @@ export const generateReadme = async (
 };
 
 export const generateMarkdown = (
-  userContent: string,
+  userContent: string | undefined,
   cmp: d.JsonDocsComponent,
   cmps: d.JsonDocsComponent[],
   readmeOutput: d.OutputTargetDocsReadme,
 ) => {
   //If the readmeOutput.dependencies is true or undefined the dependencies will be generated.
   const dependencies = readmeOutput.dependencies !== false ? depsToMarkdown(cmp, cmps) : [];
   return [
-    userContent,
+    userContent || '',
     AUTO_GENERATE_COMMENT,
     '',
     '',
@@ -78,6 +106,12 @@ const getDocsDeprecation = (cmp: d.JsonDocsComponent) => {
   return [];
 };
 
+/**
+ * Get a minimal default README for a Stencil component
+ *
+ * @param docsData documentation data for the component of interest
+ * @returns a minimal README template for that component
+ */
 const getDefaultReadme = (docsData: d.JsonDocsComponent) => {
   return [`# ${docsData.tag}`, '', '', ''].join('\n');
 };

src/declarations/stencil-public-compiler.ts

@@ -2266,6 +2266,11 @@ export interface OutputTargetDocsVscode extends OutputTargetBase {
 
 export interface OutputTargetDocsReadme extends OutputTargetBase {
   type: 'docs-readme';
+  /**
+   * The root directory where README files should be written
+   *
+   * defaults to {@link Config.srcDir}
+   */
   dir?: string;
   dependencies?: boolean;
   footer?: string;

test/docs-json/custom-readme-output/components/my-component/readme.md

@@ -0,0 +1,31 @@
+This file is in a custom location, set with `.dir` on the `docs-readme` OT.
+
+The content here above the 'auto-generation' comment shouldn't be overwritten.
+
+This is a regression test for the issue reported in ionic-team/stencil#5400.
+
+<!-- Auto Generated Below -->
+
+
+## Methods
+
+### `onDidDismiss<T>(arg: T) => Promise<ImportedInterface<T>>`
+
+A comment, which should be included, I should think!
+
+#### Parameters
+
+| Name  | Type | Description |
+| ----- | ---- | ----------- |
+| `arg` | `T`  |             |
+
+#### Returns
+
+Type: `Promise<ImportedInterface<T>>`
+
+
+
+
+----------------------------------------------
+
+*Built with [StencilJS](https://stenciljs.com/)*

test/docs-json/stencil.config.ts

@@ -8,5 +8,9 @@ export const config: Config = {
       file: 'docs.json',
       supplementalPublicTypes: 'src/components/interfaces.ts',
     },
+    {
+      type: 'docs-readme',
+      dir: 'custom-readme-output',
+    },
   ],
 };