Format values in a more intelligent way. Closes #24.

Author: ryanplusplus

spec/mach/format_value_spec.lua

@@ -0,0 +1,31 @@
+describe('mach.format_value', function()
+  local format_value = require 'mach.format_value'
+
+  it('should format basic types', function()
+    assert.are.same('3', format_value(3))
+    assert.are.same("'hello'", format_value('hello'))
+    assert.are.same('true', format_value(true))
+  end)
+
+  it('should format functions', function()
+    local f = function() end
+    assert.are.same(tostring(f), format_value(f))
+  end)
+
+  it('should format tables', function()
+    assert.are.same('{ [1] = true, [2] = false }', format_value({ true, false }))
+    assert.are.same("{ ['a'] = 1, ['b'] = 2 }", format_value({ b = 2, a = 1 }))
+    assert.are.same(
+      "{ [1] = true, ['b'] = { [4] = 'lua', ['a'] = 1 } }",
+      format_value({ b = { [4] = 'lua', a = 1 }, true })
+    )
+  end)
+
+  it('should respect __tostring when it is defined', function()
+    local value = setmetatable({}, {
+      __tostring = function() return 'foo' end
+    })
+
+    assert.are.same('foo', format_value(value))
+  end)
+end)

spec/mach_spec.lua

@@ -493,7 +493,7 @@ describe('The mach library', function()
   it('should handle table arguments in error messages', function()
     local a = {}
 
-    should_fail_with('Unexpected function call f(' .. tostring(a) ..')', function()
+    should_fail_with('Unexpected function call f({})', function()
       mach.mock_function('f')(a)
     end)
   end)
@@ -685,10 +685,10 @@ describe('The mach library', function()
     local expected_failure =
       'Unexpected arguments (4) provided to function f\n' ..
       'Incomplete calls:\n' ..
-      "\tf(<mach.match('3')>)"
+      "\tf(<mach.match({ ['3'] = 1 })>)"
 
     should_fail_with_exactly(expected_failure, function()
-      f:should_be_called_with(mach.match('3')):when(function()
+      f:should_be_called_with(mach.match({ ['3'] = 1 })):when(function()
         f(4)
       end)
     end)

src/mach/format_value.lua

@@ -1,7 +1,34 @@
-return function(v)
-  if type(v) == 'string' then
+local function pairs_sorted_by_key(t)
+  return coroutine.wrap(function()
+    local _pairs = {}
+    for k, v in pairs(t) do
+      table.insert(_pairs, { k, v })
+    end
+    table.sort(_pairs, function(x, y) return tostring(x[1]) < tostring(y[1]) end)
+    for _, pair in ipairs(_pairs) do
+      coroutine.yield(table.unpack(pair))
+    end
+  end)
+end
+
+local function format_value(v)
+  if getmetatable(v) and getmetatable(v).__tostring then
+    return tostring(v)
+  elseif type(v) == 'string' then
     return "'" .. v .. "'"
+  elseif type(v) == 'table' then
+    local elements = {}
+    for k, v in pairs_sorted_by_key(v) do
+      table.insert(elements, '[' .. format_value(k) .. '] = ' .. format_value(v))
+    end
+    if #elements > 0 then
+      return '{ ' .. table.concat(elements, ', ') .. ' }'
+    else
+      return '{}'
+    end
   else
     return tostring(v)
   end
 end
+
+return format_value