checker: "v -line-info" for a quick run to fetch info about objects on one line

vlib/v/checker/checker.v

@@ -88,7 +88,7 @@ mut:
 	// 1 for statements directly at each inner scope level;
 	// increases for `x := if cond { statement_list1} else {statement_list2}`;
 	// increases for `x := optfn() or { statement_list3 }`;
-	files                            []ast.File
+	// files                            []ast.File
 	expr_level                       int // to avoid infinite recursion segfaults due to compiler bugs
 	ensure_generic_type_level        int // to avoid infinite recursion segfaults in ensure_generic_type_specify_type_names
 	cur_orm_ts                       ast.TypeSymbol
@@ -116,6 +116,7 @@ mut:
 	inside_decl_rhs                  bool
 	inside_if_guard                  bool // true inside the guard condition of `if x := opt() {}`
 	inside_assign                    bool
+	doing_line_info                  int // a quick single file run when called with v -line-info (contains line nr to inspect)
 	is_index_assign                  bool
 	comptime_call_pos                int // needed for correctly checking use before decl for templates
 	goto_labels                      map[string]ast.GotoLabel // to check for unused goto labels
@@ -372,6 +373,11 @@ pub fn (mut c Checker) check_files(ast_files []&ast.File) {
 			c.error('a _test.v file should have *at least* one `test_` function', token.Pos{})
 		}
 	}
+	// Print line info and exit
+	if c.pref.line_info != '' && c.doing_line_info == 0 {
+		c.do_line_info(c.pref.line_info, ast_files)
+		exit(0)
+	}
 	// Make sure fn main is defined in non lib builds
 	if c.pref.build_mode == .build_module || c.pref.is_test {
 		return
@@ -3274,6 +3280,20 @@ fn (mut c Checker) at_expr(mut node ast.AtExpr) ast.Type {
 }
 
 fn (mut c Checker) ident(mut node ast.Ident) ast.Type {
+	if c.doing_line_info > 0 {
+		// Mini LS hack (v -line-info "a.v:16")
+		// println('line_nr=${node.pos.line_nr} doing line nr=${c.doing_line_info}')
+		if node.pos.line_nr == c.doing_line_info {
+			println('===')
+			sym := c.table.sym(node.obj.typ)
+			println('VAR ${node.name}:${sym.name}')
+			struct_info := sym.info as ast.Struct
+			for field in struct_info.fields {
+				field_sym := c.table.sym(field.typ)
+				println('${field.name}:${field_sym.name}')
+			}
+		}
+	}
 	// TODO: move this
 	if c.const_deps.len > 0 {
 		mut name := node.name

vlib/v/checker/line_info.v

@@ -0,0 +1,50 @@
+// Copyright (c) 2019-2023 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license that can be found in the LICENSE file.
+module checker
+
+import v.ast
+import os
+
+fn (mut c Checker) do_line_info(line string, all_ast_files []&ast.File) {
+	// println("do_line_info '${line}'")
+	format_err := 'wrong format, use `-line-info "file.v:24"'
+	vals := line.split(':')
+	if vals.len != 2 {
+		eprintln(format_err)
+		return
+	}
+	file_name := vals[0]
+	line_nr := vals[1].int() - 1
+	if !file_name.ends_with('.v') || line_nr == -1 {
+		eprintln(format_err)
+		return
+	}
+
+	// println('ok  ${c.files.len}')
+	// Find which file contains the line
+	mut found := false
+	mut found_path := ''
+	mut found_file_idx := -1
+	for i, file in all_ast_files {
+		base := os.base(file.path)
+		// println(base)
+		if base == file_name {
+			if found {
+				eprintln('more than one "${file_name}" found: "${file.path}" and "${found_path}"')
+				return
+			}
+			found = true
+			found_path = file.path
+			found_file_idx = i
+		}
+	}
+
+	if !found {
+		eprintln('file "${file_name}" not found among those parsed')
+		return
+	}
+
+	// println('found ${found_path}')
+	c.doing_line_info = line_nr
+	c.check_files([all_ast_files[found_file_idx]])
+}

vlib/v/checker/struct.v

@@ -11,6 +11,7 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 		util.timing_measure_cumulative(@METHOD)
 	}
 	mut struct_sym, struct_typ_idx := c.table.find_sym_and_type_idx(node.name)
+	// struct_sym.jj0
 	mut has_generic_types := false
 	if mut struct_sym.info is ast.Struct {
 		if node.language == .v && !c.is_builtin_mod && !struct_sym.info.is_anon {

vlib/v/pref/pref.v

@@ -186,6 +186,7 @@ pub mut:
 	out_name_c       string // full os.real_path to the generated .tmp.c file; set by builder.
 	out_name         string
 	path             string // Path to file/folder to compile
+	line_info        string // `-line-info="file.v:28"`: for "mini VLS" (shows information about objects on provided line)
 	//
 	run_only []string // VTEST_ONLY_FN and -run-only accept comma separated glob patterns.
 	// Only test_ functions that match these patterns will be run. -run-only is valid only for _test.v files.
@@ -805,6 +806,10 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 				res.cmain = cmdline.option(current_args, '-cmain', '')
 				i++
 			}
+			'-line-info' {
+				res.line_info = cmdline.option(current_args, arg, '')
+				i++
+			}
 			'-use-coroutines' {
 				res.use_coroutines = true
 				$if macos || linux {