vdoc: fix symbol filtering (#9210)

cmd/tools/vdoc/vdoc.v

@@ -292,7 +292,7 @@ fn (mut vd VDoc) generate_docs_from_file() {
 				exit(1)
 			}
 		} else {
-			dcs = doc.generate(dirpath, cfg.pub_only, true) or {
+			dcs = doc.generate(dirpath, cfg.pub_only, true, cfg.symbol_name) or {
 				vd.emit_generate_err(err)
 				exit(1)
 			}
@@ -316,13 +316,6 @@ fn (mut vd VDoc) generate_docs_from_file() {
 					}
 				}
 			}
-			if !cfg.is_multi && cfg.symbol_name.len > 0 {
-				if cfg.symbol_name in dcs.contents {
-					for _, c in dcs.contents[cfg.symbol_name].children {
-						dcs.contents[c.name] = c
-					}
-				}
-			}
 		}
 		vd.docs << dcs
 	}
@@ -449,7 +442,9 @@ fn parse_arguments(args []string) Config {
 			else {
 				if cfg.input_path.len < 1 {
 					cfg.input_path = arg
-				} else {
+				} else if !cfg.is_multi {
+					// Symbol name filtering should not be enabled
+					// in multi-module documentation mode.
 					cfg.symbol_name = arg
 				}
 				if i == args.len - 1 {

vlib/v/doc/doc.v

@@ -67,6 +67,7 @@ pub mut:
 	parent_mod_name     string
 	orig_mod_name       string
 	extract_vars        bool
+	filter_symbol_names []string
 }
 
 pub struct DocPos {
@@ -230,6 +231,10 @@ pub fn (mut d Doc) stmt(stmt ast.Stmt, filename string) ?DocNode {
 			return error('invalid stmt type to document')
 		}
 	}
+	included := node.name in d.filter_symbol_names || node.parent_name in d.filter_symbol_names
+	if d.filter_symbol_names.len != 0 && !included {
+		return error('not included in the list of symbol names')
+	}
 	return node
 }
 
@@ -428,10 +433,11 @@ pub fn (mut d Doc) file_asts(file_asts []ast.File) ? {
 
 // generate documents a certain file directory and returns an
 // instance of `Doc` if it is successful. Otherwise, it will  throw an error.
-pub fn generate(input_path string, pub_only bool, with_comments bool) ?Doc {
+pub fn generate(input_path string, pub_only bool, with_comments bool, filter_symbol_names ...string) ?Doc {
 	mut doc := new(input_path)
 	doc.pub_only = pub_only
 	doc.with_comments = with_comments
+	doc.filter_symbol_names = filter_symbol_names.filter(it.len != 0)
 	doc.generate() ?
 	return doc
 }