From 5e657c65047c3f1e6546bc908f816c49ab02938d Mon Sep 17 00:00:00 2001
From: Jon Michael Aanes <jonjmaa@gmail.com>
Date: Sun, 22 Oct 2017 11:55:05 +0200
Subject: [PATCH] More robust `super_tostring`.

---
 analyze_structure.lua    | 8 ++++++--
 test/test_resilience.lua | 9 +++------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/analyze_structure.lua b/analyze_structure.lua
index 3799b9a..56075dd 100644
--- a/analyze_structure.lua
+++ b/analyze_structure.lua
@@ -42,6 +42,8 @@ local LEAF_VALUE_TYPES = {
 local SHORT_STRING_MAX_LEN = 7
 local MINIMUM_NUMBER_OF_SET_ELEMENTS = 2
 
+local RECURSIVE_TOSTRING_TIMEOUT = 10
+
 --------------------------------------------------------------------------------
 
 local function is_identifier(s)
@@ -226,12 +228,14 @@ local function super_tostring (t)
     -- function cannot find a string.
 
     local seen = { [t] = true }
-    while true do
-        local nt = tostring(t)
+    for i = 1, RECURSIVE_TOSTRING_TIMEOUT do
+        local success, nt  =  pcall(tostring, t)
+        if not success then  return 'error on tostring: '..tostring(nt)  end
         if type(nt) == 'string' or nt == nil then  return tostring(nt)  end
         if seen[nt] then  return nil  end
         seen[nt], t  =  true, nt
     end
+    return nil
 end
 
 --------------------------------------------------------------------------------
diff --git a/test/test_resilience.lua b/test/test_resilience.lua
index 3e72b52..d4c0e10 100644
--- a/test/test_resilience.lua
+++ b/test/test_resilience.lua
@@ -161,13 +161,10 @@ end
 --------------------------------------------------------------------------------
 -- Strange metatable
 
-SUITE:addTest('Metatable: Error on %s operator', function (op)
-    pretty( setmetatable( { a = 2, b = 4, 1, 2, 3 } , {['__'..op] = function() error 'This should be unreachable!' end}) )
+SUITE:addTest('Metatable: Error on operator', function (op)
+    pretty( setmetatable( { a = 2, b = 4, 1, 2, 3 } , {[op] = function() error 'This should be unreachable!' end}) )
     assert(true)
-end, { data = {
-    {'add'}, {'sub'}, {'mul'}, {'div'}, {'mod'},{'pow'}, {'unm'}, {'concat'},
-    {'len'}, {'eq'}, {'lt'}, {'le'}, {'index'}, {'newindex'}, {'call'} }
-})
+end, { data = { '__add', '__sub', '__mul', '__div', '__mod', '__pow', '__unm', '__concat','__len', '__eq', '__lt', '__le', '__index', '__newindex', '__call', '__tostring' } })
 
 SUITE:addTest('Metatable: # returns bogus length', function ()
     assert_equal('{ 1, 2, 3, 4 }', pretty( setmetatable({ 1, 2, 3, 4 }, {__len = function() return 2 end})))