From d51277e2fc22cbccc4ec659d07f2a0f78177a419 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Fri, 15 Aug 2025 19:00:51 +0300
Subject: [PATCH] vls: autocomplete for function signatures

---
 vlib/v/checker/autocomplete.v | 23 +++++++++++++++++++++++
 vlib/v/checker/checker.v      |  4 ++++
 vlib/v/pref/line_info.v       | 35 ++++++++++++++++++++++++++++-------
 vlib/v/pref/pref.v            | 10 ----------
 4 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/vlib/v/checker/autocomplete.v b/vlib/v/checker/autocomplete.v
index 60d8612be8..aa47a579ea 100644
--- a/vlib/v/checker/autocomplete.v
+++ b/vlib/v/checker/autocomplete.v
@@ -21,6 +21,17 @@ fn abs(a int) int {
 pub fn (mut c Checker) run_ac(ast_file &ast.File) {
 }
 
+pub fn (mut c Checker) autocomplete_for_fn_call_expr() {
+	// println(c.pref.linfo.expr)
+	fn_name := c.pref.linfo.expr.replace('()', '').trim_space()
+	f := c.table.find_fn(fn_name) or {
+		println('failed to find fn "${fn_name}"')
+		return
+	}
+	res := c.build_fn_summary(f)
+	println(res)
+}
+
 fn (mut c Checker) ident_autocomplete(node ast.Ident) {
 	// Mini LS hack (v -line-info "a.v:16")
 	if c.pref.is_verbose {
@@ -45,6 +56,7 @@ fn (mut c Checker) ident_autocomplete(node ast.Ident) {
 	}
 	// Module autocomplete
 	// `os. ...`
+	// println(node)
 	if node.name == '' && node.mod != 'builtin' {
 		c.module_autocomplete(node)
 		return
@@ -165,3 +177,14 @@ fn build_method_summary(method ast.Fn) string {
 	}
 	return s + ')'
 }
+
+fn (c &Checker) build_fn_summary(method ast.Fn) string {
+	mut s := method.name + '('
+	for i, param in method.params {
+		s += param.name + ' ' + c.table.type_to_str(param.typ)
+		if i < method.params.len - 1 {
+			s += ', '
+		}
+	}
+	return s + ')'
+}
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 98ab39bd80..08369f313f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -433,6 +433,10 @@ pub fn (mut c Checker) check_files(ast_files []&ast.File) {
 		// println('setting is_running=true,  pref.path=${c.pref.linfo.path} curdir' + os.getwd())
 		c.pref.linfo.is_running = true
 		// println('linfo path=${c.pref.linfo.path}')
+		if c.pref.linfo.expr.contains('()') {
+			c.autocomplete_for_fn_call_expr()
+			exit(0)
+		}
 		for i, file in ast_files {
 			// println(file.path)
 			if file.path == c.pref.linfo.path {
diff --git a/vlib/v/pref/line_info.v b/vlib/v/pref/line_info.v
index 88d7b16b05..b7a00ae27a 100644
--- a/vlib/v/pref/line_info.v
+++ b/vlib/v/pref/line_info.v
@@ -2,6 +2,16 @@
 // Use of this source code is governed by an MIT license that can be found in the LICENSE file.
 module pref
 
+pub struct LineInfo {
+pub mut:
+	line_nr      int    // a quick single file run when called with v -line-info (contains line nr to inspect)
+	path         string // same, but stores the path being parsed
+	expr         string // "os.foo()" V code (expression) which needs autocomplete, right only function calls
+	col          int
+	is_running   bool            // so that line info is fetched only on the second checker run
+	vars_printed map[string]bool // to avoid dups
+}
+
 fn (mut p Preferences) parse_line_info(line string) {
 	// println("parse_line_info '${line}'")
 	format_err := 'wrong format, use `-line-info "file.v:24:7"'
@@ -12,16 +22,27 @@ fn (mut p Preferences) parse_line_info(line string) {
 	}
 	file_name := vals[0]
 	line_nr := vals[1].int() - 1
-	col := vals[2].int() - 1
-	// expr := vals[2]
+
 	if !file_name.ends_with('.v') || line_nr == -1 {
 		eprintln(format_err)
 		return
 	}
-	p.linfo = LineInfo{
-		line_nr: line_nr
-		path:    file_name
-		// expr:    expr
-		col: col
+
+	// Third value can be a column or expression for autocomplete like `os.create()`
+	third := vals[2]
+	if third[0].is_digit() {
+		col := vals[2].int() - 1
+		p.linfo = LineInfo{
+			line_nr: line_nr
+			path:    file_name
+			col:     col
+		}
+	} else {
+		expr := vals[2]
+		p.linfo = LineInfo{
+			line_nr: line_nr
+			path:    file_name
+			expr:    expr
+		}
 	}
 }
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 83320e4a4f..fcceb679ea 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -262,16 +262,6 @@ pub mut:
 	json_errors bool // -json-errors, for VLS and other tools
 }
 
-pub struct LineInfo {
-pub mut:
-	line_nr int    // a quick single file run when called with v -line-info (contains line nr to inspect)
-	path    string // same, but stores the path being parsed
-	// expr         string          // "foo" or "foo.bar" V code (expression) which needs autocomplete
-	col          int
-	is_running   bool            // so that line info is fetched only on the second checker run
-	vars_printed map[string]bool // to avoid dups
-}
-
 pub fn parse_args(known_external_commands []string, args []string) (&Preferences, string) {
 	return parse_args_and_show_errors(known_external_commands, args, false)
 }