src/ln: support filters

spec/ln_spec.lua

@@ -8,6 +8,8 @@ describe("ln", function()
 
     it("has default_logger", function()
       assert.truthy(ln.default_logger)
+      assert.truthy(ln.default_logger.formatter)
+      assert.truthy(ln.default_logger.filters)
     end)
 
     it("has LogfmtFormatter", function()
@@ -29,21 +31,32 @@ describe("ln", function()
 
   describe("default logger operations", function()
     local lgr = ln.default_logger
+    local msg
+    lgr.filters = {
+      function(message) msg = message end,
+    }
+    
     it("can log", function()
       lgr:log {foo = "bar"}
+      assert.truthy(string.find(msg, 'foo=bar'))
     end)
 
     it("can error", function()
-      lgr:err("vibe check failed", {foo = "bar"})
+      lgr:err("vibe check failed", {foo = "baz"})
+      assert.truthy(string.find(msg, 'foo=baz'))
+      assert.truthy(string.find(msg, 'vibe check failed'))
     end)
 
     it("takes multiple tables", function()
       lgr:log({foo = "bar"}, {baz = "boz"})
+      assert.truthy(string.find(msg, 'foo=bar'))
+      assert.truthy(string.find(msg, 'baz=boz'))
     end)
 
     it("lets you override the formatter", function()
       lgr.formatter = ln.JSONFormatter:new()
       lgr:log {foo = "bar"}
+      assert.truthy(string.find(msg, "{"))
     end)
   end)
 
@@ -59,14 +72,24 @@ describe("ln", function()
       assert.truthy(string.find(msg, 'foo="bar with spaces"'))
     end)
   end)
-           
+
   describe("logger options", function()
+    local msg
+    local filter_func = function(message) msg = message end
     local lgr = ln.Logger:new {
-      formatter = ln.LogfmtFormatter:new()
+      formatter = ln.LogfmtFormatter:new(),
+      filters = {
+        filter_func,
+      }
     }
     
     it("sets the formatter to non-nil", function()
       assert.truthy(lgr.formatter)
     end)
+    
+    it("respects filters", function()
+      lgr:log {foo = "bar"}
+      assert.truthy(string.find(msg, 'foo=bar'))
+    end)
   end)
 end)

src/ln.lua

@@ -63,17 +63,25 @@ function Logger:log(...)
     end
   end
 
-  message = self.formatter:format(result)
-
-  print(message)
+  local message = self.formatter:format(result)
+  for _, v in pairs(self.filters) do
+    v(message)
+  end
 end
 
 function Logger:new(o)
   if o == nil then
-    o = {
-      formatter = LogfmtFormatter:new()
-    }
+    o = {}
   end
+  
+  if o.formatter == nil then
+    o.formatter = LogfmtFormatter:new()
+  end
+  
+  if o.filters == nil then
+    o.filters = {print}
+  end
+  
   setmetatable(o, self)
   self.__index = self
   return o