fix(md)!: warn if region not found, strip #regions

when a region is not in the source file,
instead of including the whole file,
warn that the #region was not found in it.

fix #4625

---

`<<<` snippets now also strip out all #region markers:

```file.ts
// #region A
// #region B
console.log("Hello, World!");
// #endregion
// #endregion
```

<<< file.ts#A
...does not include "#region B" anymore

Author: its-miroma

__tests__/e2e/markdown-extensions/markdown-extensions.test.ts

@@ -216,7 +216,7 @@ describe('Line Numbers', () => {
 describe('Import Code Snippets', () => {
   test('basic', async () => {
     const lines = page.locator('#basic-code-snippet + div code > span')
-    expect(await lines.count()).toBe(11)
+    expect(await lines.count()).toBe(9)
   })
 
   test('specify region', async () => {
@@ -269,7 +269,7 @@ describe('Code Groups', () => {
 
     // blocks
     const blocks = div.locator('.blocks > div')
-    expect(await blocks.nth(0).locator('code > span').count()).toBe(11)
+    expect(await blocks.nth(0).locator('code > span').count()).toBe(9)
     expect(await getClassList(blocks.nth(1))).toContain('line-numbers-mode')
     expect(await getClassList(blocks.nth(1))).toContain('language-ts')
     expect(await blocks.nth(1).locator('code > span').count()).toBe(3)

__tests__/unit/node/markdown/plugins/snippet.test.ts

@@ -1,7 +1,8 @@
 import {
   dedent,
   findRegions,
-  rawPathToToken
+  rawPathToToken,
+  stripRegionMarkers
 } from 'node/markdown/plugins/snippet'
 import { expect } from 'vitest'
 
@@ -406,5 +407,74 @@ describe('node/markdown/plugins/snippet', () => {
         expect(extracted).toBe(expected)
       }
     })
+
+    it('handles region names with hyphens and special characters', () => {
+      const lines = [
+        '// #region complex-name_123',
+        'const x = 1;',
+        '// #endregion complex-name_123'
+      ]
+      const result = findRegions(lines, 'complex-name_123')
+      expect(result).toHaveLength(1)
+      if (result) {
+        const extracted = result
+          .flatMap((r) =>
+            lines
+              .slice(r.start, r.end)
+              .filter((l) => !(r.re.start.test(l) || r.re.end.test(l)))
+          )
+          .join('\n')
+        expect(extracted).toBe('const x = 1;')
+      }
+    })
+  })
+
+  describe('stripRegionMarkers', () => {
+    it('removes #region and #endregion lines', () => {
+      const src = [
+        '// #region A',
+        '// #region B',
+        'console.log("Hello, World!");',
+        '// #endregion B',
+        '// #endregion A'
+      ].join('\n')
+      expect(stripRegionMarkers(src)).toBe('console.log("Hello, World!");')
+    })
+
+    it('removes region markers for various syntaxes', () => {
+      const src = [
+        '<!-- #region html -->',
+        '<div>hi</div>',
+        '<!-- #endregion html -->',
+        '/* #region css */',
+        'body {}',
+        '/* #endregion css */',
+        '#pragma region cpp',
+        'int main(){}',
+        '#pragma endregion cpp',
+        '::#region bat',
+        'ECHO ON',
+        'REM #endregion bat'
+      ].join('\n')
+      const out = stripRegionMarkers(src)
+      expect(out).not.toContain('#region')
+      expect(out).not.toContain('#endregion')
+      expect(out).toContain('<div>hi</div>')
+      expect(out).toContain('body {}')
+      expect(out).toContain('int main(){}')
+      expect(out).toContain('ECHO ON')
+    })
+
+    it('removes markers even if indented or with extra spaces', () => {
+      const src = [
+        '   //   #region   spaced  ',
+        '\t/* #region */',
+        'code();',
+        '   // #endregion spaced',
+        '/*    #endregion   */'
+      ].join('\n')
+      const out = stripRegionMarkers(src)
+      expect(out.trim()).toBe('code();')
+    })
   })
 })

src/node/markdown/plugins/snippet.ts

@@ -126,6 +126,18 @@ export function findRegions(lines: string[], regionName: string) {
   return returned
 }
 
+export function stripRegionMarkers(content: string): string {
+  return content
+    .split('\n')
+    .filter((l) => {
+      for (const m of markers) {
+        if (m.start.test(l) || m.end.test(l)) return false
+      }
+      return true
+    })
+    .join('\n')
+}
+
 export const snippetPlugin = (md: MarkdownItAsync, srcDir: string) => {
   const parser: RuleBlock = (state, startLine, endLine, silent) => {
     const CH = '<'.charCodeAt(0)
@@ -218,7 +230,14 @@ export const snippetPlugin = (md: MarkdownItAsync, srcDir: string) => {
             )
             .join('\n')
         )
+        content = stripRegionMarkers(content)
+      } else {
+        token.content = `Could not find region #${regionName} in file ${src}`
+        token.info = ''
+        return fence(...args)
       }
+    } else {
+      content = stripRegionMarkers(content)
     }
 
     token.content = content

src/node/utils/processIncludes.ts

@@ -71,9 +71,13 @@ export function processIncludes(
           }
         }
 
-        content = regions
-          .flatMap((region) => lines.slice(region.start, region.end))
-          .join('\n')
+        if (regions.length > 0) {
+          content = regions
+            .flatMap((region) => lines.slice(region.start, region.end))
+            .join('\n')
+        } else {
+          content = `Could not find region or heading ${region[0]} in file ${includePath}`
+        }
       }
 
       if (range) {