From 8327c9afc1ccd870190752dea5f71828a98546f2 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Sat, 20 Feb 2021 17:35:29 +0200
Subject: [PATCH] checker: support a custom `[deprecated: 'message']`

---
 vlib/v/checker/checker.v                      |  8 +++++++-
 .../tests/use_deprecated_function_warning.out | 19 +++++++++++++------
 .../tests/use_deprecated_function_warning.vv  | 16 +++++++++++++---
 3 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 5ef8c2e620..6ce3198c58 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1784,7 +1784,13 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 			call_expr.pos)
 	}
 	if f.is_deprecated {
-		c.warn('function `$f.name` has been deprecated', call_expr.pos)
+		mut deprecation_message := 'function `$f.name` has been deprecated'
+		for d in f.attrs {
+			if d.name == 'deprecated' && d.arg != '' {
+				deprecation_message += '; $d.arg'
+			}
+		}
+		c.warn(deprecation_message, call_expr.pos)
 	}
 	if f.is_unsafe && !c.inside_unsafe
 		&& (f.language != .c || (f.name[2] in [`m`, `s`] && f.mod == 'builtin')) {
diff --git a/vlib/v/checker/tests/use_deprecated_function_warning.out b/vlib/v/checker/tests/use_deprecated_function_warning.out
index 9e3c353a12..cce53f6e23 100644
--- a/vlib/v/checker/tests/use_deprecated_function_warning.out
+++ b/vlib/v/checker/tests/use_deprecated_function_warning.out
@@ -1,6 +1,13 @@
-vlib/v/checker/tests/use_deprecated_function_warning.vv:3:5: error: function `os.cp_r` has been deprecated
-    1 | import os
-    2 | fn main() {
-    3 |     os.cp_r('./aa', './bb', true)
-      |        ~~~~~~~~~~~~~~~~~~~~~~~~~~
-    4 | }
+vlib/v/checker/tests/use_deprecated_function_warning.vv:12:2: error: function `xyz` has been deprecated
+   10 | 
+   11 | fn main() {
+   12 |     xyz()
+      |     ~~~~~
+   13 |     abc()
+   14 | }
+vlib/v/checker/tests/use_deprecated_function_warning.vv:13:2: error: function `abc` has been deprecated; use foo2 instead
+   11 | fn main() {
+   12 |     xyz()
+   13 |     abc()
+      |     ~~~~~
+   14 | }
diff --git a/vlib/v/checker/tests/use_deprecated_function_warning.vv b/vlib/v/checker/tests/use_deprecated_function_warning.vv
index 7f45b782d4..6a72a2ad92 100644
--- a/vlib/v/checker/tests/use_deprecated_function_warning.vv
+++ b/vlib/v/checker/tests/use_deprecated_function_warning.vv
@@ -1,4 +1,14 @@
-import os
-fn main() {
-	os.cp_r('./aa', './bb', true)
+[deprecated]
+fn xyz() {
+	println('hi')
+}
+
+[deprecated: 'use foo2 instead']
+fn abc() {
+	println('hi')
+}
+
+fn main() {
+	xyz()
+	abc()
 }