From 936a1afbc2b4e4f6fefed945fb1449197ba48c13 Mon Sep 17 00:00:00 2001
From: Manfred Touron <94029+moul@users.noreply.github.com>
Date: Wed, 12 Jan 2022 09:15:26 +0000
Subject: [PATCH] feat: add CheckLevel helper

Signed-off-by: Manfred Touron <94029+moul@users.noreply.github.com>
---
 README.md         |  3 +++
 zapfilter.go      |  5 +++++
 zapfilter_test.go | 31 +++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/README.md b/README.md
index de2ec7f..5ee2d7f 100644
--- a/README.md
+++ b/README.md
@@ -70,6 +70,9 @@ func CheckAnyLevel(logger *zap.Logger) bool
     CheckAnyLevel determines whether at least one log level isn't filtered-out
     by the logger.
 
+func CheckLevel(logger *zap.Logger, level zapcore.Level) bool
+    CheckLevel determines whether a specific log level would produce log or not.
+
 func NewFilteringCore(next zapcore.Core, filter FilterFunc) zapcore.Core
     NewFilteringCore returns a core middleware that uses the given filter
     function to determine whether to actually call Write on the next core in the
diff --git a/zapfilter.go b/zapfilter.go
index f948c1a..087e0e0 100644
--- a/zapfilter.go
+++ b/zapfilter.go
@@ -35,6 +35,11 @@ func CheckAnyLevel(logger *zap.Logger) bool {
 	return false
 }
 
+// CheckLevel determines whether a specific log level would produce log or not.
+func CheckLevel(logger *zap.Logger, level zapcore.Level) bool {
+	return logger.Check(level, "") != nil
+}
+
 type filteringCore struct {
 	next   zapcore.Core
 	filter FilterFunc
diff --git a/zapfilter_test.go b/zapfilter_test.go
index 3f25c6b..3a2fb71 100644
--- a/zapfilter_test.go
+++ b/zapfilter_test.go
@@ -436,6 +436,37 @@ func ExampleCheckAnyLevel() {
 	// true
 }
 
+func ExampleCheckLevel() {
+	c := zap.NewExample().Core()
+	logger := zap.New(zapfilter.NewFilteringCore(c, zapfilter.MustParseRules("debug:*.* info:demo*")))
+
+	fmt.Println(zapfilter.CheckLevel(logger, zap.DebugLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("demo"), zap.DebugLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("blahdemo"), zap.DebugLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("demoblah"), zap.DebugLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("blah"), zap.DebugLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("blah.blah"), zap.DebugLevel))
+	fmt.Println(zapfilter.CheckLevel(logger, zap.InfoLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("demo"), zap.InfoLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("blahdemo"), zap.InfoLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("demoblah"), zap.InfoLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("blah"), zap.InfoLevel))
+	fmt.Println(zapfilter.CheckLevel(logger.Named("blah.blah"), zap.InfoLevel))
+	// Output:
+	// false
+	// false
+	// false
+	// false
+	// false
+	// true
+	// false
+	// true
+	// false
+	// true
+	// false
+	// false
+}
+
 func Example_with() {
 	core := zap.NewExample().Core()
 	logger := zap.New(zapfilter.NewFilteringCore(core, zapfilter.ByNamespaces("demo1.*,demo3.*")))