fmt: do not generate `import` statements for auto imports (#7966)

doc/docs.md

@@ -2228,8 +2228,6 @@ a property of the individual channel object. Channels can be passed to coroutine
 variables:
 
 ```v
-import sync
-
 fn f(ch chan int) {
 	// ...
 }
@@ -2331,8 +2329,6 @@ if select {
 
 For special purposes there are some builtin properties and methods:
 ```v nofmt
-import sync
-
 struct Abc{x int}
 
 a := 2.13

vlib/builtin/array_test.v

@@ -1,5 +1,3 @@
-import sync
-
 fn test_pointer() {
 	mut arr := []&int{}
 	a := 1

vlib/v/ast/ast.v

@@ -461,6 +461,7 @@ pub mut:
 	scope            &Scope
 	stmts            []Stmt   // all the statements in the source file
 	imports          []Import // all the imports
+	auto_imports     []string // imports that were implicitely added
 	imported_symbols map[string]string // used for `import {symbol}`, it maps symbol => module.symbol
 	errors           []errors.Error    // all the checker errors in the file
 	warnings         []errors.Warning  // all the checker warings in the file

vlib/v/fmt/fmt.v

@@ -38,7 +38,7 @@ pub mut:
 	file              ast.File
 	did_imports       bool
 	is_assign         bool
-	auto_imports      []string // automatically inserted imports that the user forgot to specify
+	auto_imports      []string // automatically inserted imports that the user does not need to specify
 	import_pos        int      // position of the imports in the resulting string for later autoimports insertion
 	used_imports      []string // to remove unused imports
 	is_debug          bool
@@ -83,6 +83,7 @@ pub fn (mut f Fmt) process_file_imports(file &ast.File) {
 			f.mod2alias[sym.name] = sym.name
 		}
 	}
+	f.auto_imports = file.auto_imports
 }
 
 pub fn (mut f Fmt) write(s string) {
@@ -201,8 +202,8 @@ pub fn (mut f Fmt) imports(imports []ast.Import) {
 	if f.did_imports || imports.len == 0 {
 		return
 	}
-	// f.import_pos = f.out.len
 	f.did_imports = true
+	mut num_imports := 0
 	/*
 	if imports.len == 1 {
 		imp_stmt_str := f.imp_stmt_str(imports[0])
@@ -215,12 +216,16 @@ pub fn (mut f Fmt) imports(imports []ast.Import) {
 			// TODO bring back once only unused imports are removed
 			// continue
 		}
-		// f.out_imports.write('\t')
-		// f.out_imports.writeln(f.imp_stmt_str(imp))
+		if imp.mod in f.auto_imports && imp.mod !in f.used_imports {
+			continue
+		}
 		f.out_imports.write('import ')
 		f.out_imports.writeln(f.imp_stmt_str(imp))
+		num_imports++
 	}
+	if num_imports > 0 {
 		f.out_imports.writeln('')
+	}
 	// f.out_imports.writeln(')\n')
 	// }
 }
@@ -1678,13 +1683,10 @@ pub fn (mut f Fmt) call_expr(node ast.CallExpr) {
 			// a `node.left` expression. Import `time` automatically.
 			// TODO fetch all available modules
 			if node.left.name in ['time', 'os', 'strings', 'math', 'json', 'base64'] {
-				if node.left.name !in f.auto_imports {
-					f.auto_imports << node.left.name
 				f.file.imports << ast.Import{
 					mod: node.left.name
 					alias: node.left.name
 				}
-				}
 				// for imp in f.file.imports {
 				// println(imp.mod)
 				// }

vlib/v/fmt/tests/chan_init_keep.vv

@@ -1,5 +1,3 @@
-import sync
-
 struct FSMEvent {
 	x int
 }

vlib/v/fmt/tests/shared_expected.vv

@@ -1,4 +1,3 @@
-import sync
 import time
 
 struct St {

vlib/v/parser/module.v

@@ -42,6 +42,9 @@ fn (mut p Parser) register_auto_import(alias string) {
 		}
 		p.ast_imports << node
 	}
+	if alias !in p.auto_imports {
+		p.auto_imports << alias
+	}
 	p.register_used_import(alias)
 }
 

vlib/v/parser/parser.v

@@ -53,6 +53,7 @@ mut:
 	imports           map[string]string // alias => mod_name
 	ast_imports       []ast.Import      // mod_names
 	used_imports      []string // alias
+	auto_imports      []string // imports, the user does not need to specify
 	imported_symbols  map[string]string
 	is_amp            bool // for generating the right code for `&Foo{}`
 	returns           bool
@@ -232,6 +233,7 @@ pub fn (mut p Parser) parse() ast.File {
 		mod: module_decl
 		imports: p.ast_imports
 		imported_symbols: p.imported_symbols
+		auto_imports: p.auto_imports
 		stmts: stmts
 		scope: p.scope
 		global_scope: p.global_scope

vlib/x/websocket/io.v

@@ -2,7 +2,6 @@ module websocket
 
 import net
 import time
-import sync
 
 // socket_read reads from socket into the provided buffer
 fn (mut ws Client) socket_read(mut buffer []byte) ?int {

vlib/x/websocket/websocket_client.v

@@ -7,7 +7,6 @@ import x.openssl
 import net.urllib
 import time
 import log
-import sync
 import rand
 
 const (

vlib/x/websocket/websocket_server.v

@@ -3,7 +3,6 @@ module websocket
 import net
 import x.openssl
 import log
-import sync
 import time
 import rand