From 50c7c915ee2fa239043d5456237f5145d064089b Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Tue, 19 Nov 2024 14:09:18 -0300
Subject: Debug information about extra arguments from __call

'debug.getinfo' can return number of extra arguments added to a call by
a chain of __call metavalues. That information is being used to improve
error messages about errors in these extra arguments.
---
 testes/calls.lua  | 11 +++++++++++
 testes/db.lua     |  3 +++
 testes/errors.lua | 25 +++++++++++++++++++++++++
 3 files changed, 39 insertions(+)

(limited to 'testes')

diff --git a/testes/calls.lua b/testes/calls.lua
index 12312d60..31028215 100644
--- a/testes/calls.lua
+++ b/testes/calls.lua
@@ -204,6 +204,17 @@ do   print"testing chains of '__call'"
     assert(Res[i][1] == i)
   end
   assert(Res[N + 1] == "a" and Res[N + 2] == "b" and Res[N + 3] == "c")
+
+  local function u (...)
+    local n = debug.getinfo(1, 't').extraargs
+    assert(select("#", ...) == n)
+    return n
+  end
+
+  for i = 0, N do
+    assert(u() == i)
+    u = setmetatable({}, {__call = u})
+  end
 end
 
 
diff --git a/testes/db.lua b/testes/db.lua
index 49ff8e3e..fc0db9ea 100644
--- a/testes/db.lua
+++ b/testes/db.lua
@@ -624,6 +624,9 @@ local function f (x)
     end
 end
 
+assert(debug.getinfo(print, 't').istailcall == false)
+assert(debug.getinfo(print, 't').extraargs == 0)
+
 function g(x) return f(x) end
 
 function g1(x) g(x) end
diff --git a/testes/errors.lua b/testes/errors.lua
index 80d91a92..0925fe58 100644
--- a/testes/errors.lua
+++ b/testes/errors.lua
@@ -117,6 +117,31 @@ else
     return 1
   ]]
   assert(string.find(res, "xuxu.-main chunk"))
+
+  do   -- tests for error messages about extra arguments from __call
+    local function createobj (n)
+      -- function that raises an error on its n-th argument
+      local code = string.format("argerror %d 'msg'", n)
+      local func = T.makeCfunc(code)
+      -- create a chain of 2 __call objects
+      local M = setmetatable({}, {__call = func})
+      M = setmetatable({}, {__call = M})
+      -- put it as a method for a new object
+      return {foo = M}
+    end
+
+  _G.a = createobj(1)   -- error in first (extra) argument
+  checkmessage("a:foo()", "bad extra argument #1")
+
+  _G.a = createobj(2)   -- error in second (extra) argument
+  checkmessage("a:foo()", "bad extra argument #2")
+
+  _G.a = createobj(3)   -- error in self (after two extra arguments)
+  checkmessage("a:foo()", "bad self")
+
+  _G.a = createobj(4)  -- error in first regular argument (after self)
+  checkmessage("a:foo()", "bad argument #1")
+  end
 end
 
 
-- 
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