fix(md)!: warn if region not found

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

src/node/markdown/plugins/snippet.ts

@@ -218,6 +218,10 @@ export const snippetPlugin = (md: MarkdownItAsync, srcDir: string) => {
             )
             .join('\n')
         )
+      } else {
+        token.content = `No region #${region} found in path: ${src}`
+        token.info = ''
+        return fence(...args)
       }
     }
 

src/node/utils/processIncludes.ts

@@ -70,9 +70,13 @@ 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 = `No region or heading #${region} found in path: ${includePath}`
+      }
     }
 
     if (range) {