Various improvements (#42)

* doc: add README sections for HandlerNameFunc and RequestPathFunc options

* refactor: extract options in their own file

* refactor: type options for better readability

* feat: push coverage to 100%

README.md

@@ -182,6 +182,48 @@ p := ginprom.New(
 r.Use(p.Instrument())
 ```
 
+### HandlerNameFunc
+
+Change the way the `handler` label is computed. By default, the `(*gin.Context).HandlerName`
+function is used.
+This option is useful when wanting to group different functions under
+the same `handler` label or when using `gin` with decorated handlers.
+
+```go
+r := gin.Default()
+p := ginprom.New(
+	HandlerNameFunc(func (c *gin.Context) string {
+		return "my handler"
+	}),
+)
+r.Use(p.Instrument())
+```
+
+### RequestPathFunc
+
+Change how the `path` label is computed. By default, the `(*gin.Context).FullPath` function 
+is used.
+This option is useful when wanting to group different requests under the same `path`
+label or when wanting to process unknown routes (the default `(*gin.Context).FullPath` returns
+an empty string for unregistered routes). Note that requests for which `f` returns the empty
+string are ignored.
+
+To specifically ignore certain paths, see the [Ignore](#ignore) option.
+
+```go
+r := gin.Default()
+p := ginprom.New(
+	// record a metric for unregistered routes under the path label "<unknown>"
+	RequestPathFunc(func (c *gin.Context) string {
+		if fullpath := c.FullPath(); fullpath != "" {
+			return fullpath
+		}
+		return "<unknown>"
+	}),
+)
+r.Use(p.Instrument())
+```
+
 ### Ignore
 
 Ignore allows to completely ignore some routes. Even though you can apply the

options.go

@@ -0,0 +1,144 @@
+package ginprom
+
+import (
+	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type PrometheusOption func(*Prometheus)
+
+// Path is an option allowing to set the metrics path when initializing with New.
+func Path(path string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.MetricsPath = path
+	}
+}
+
+// Ignore is used to disable instrumentation on some routes.
+func Ignore(paths ...string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.Ignored.Lock()
+		defer p.Ignored.Unlock()
+		for _, path := range paths {
+			p.Ignored.values[path] = true
+		}
+	}
+}
+
+// BucketSize is used to define the default bucket size when initializing with
+// New.
+func BucketSize(b []float64) PrometheusOption {
+	return func(p *Prometheus) {
+		p.BucketsSize = b
+	}
+}
+
+// Subsystem is an option allowing to set the subsystem when initializing
+// with New.
+func Subsystem(sub string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.Subsystem = sub
+	}
+}
+
+// Namespace is an option allowing to set the namespace when initializing
+// with New.
+func Namespace(ns string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.Namespace = ns
+	}
+}
+
+// Token is an option allowing to set the bearer token in prometheus
+// with New.
+// Example: ginprom.New(ginprom.Token("your_custom_token"))
+func Token(token string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.Token = token
+	}
+}
+
+// RequestCounterMetricName is an option allowing to set the request counter metric name.
+func RequestCounterMetricName(reqCntMetricName string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.RequestCounterMetricName = reqCntMetricName
+	}
+}
+
+// RequestDurationMetricName is an option allowing to set the request duration metric name.
+func RequestDurationMetricName(reqDurMetricName string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.RequestDurationMetricName = reqDurMetricName
+	}
+}
+
+// RequestSizeMetricName is an option allowing to set the request size metric name.
+func RequestSizeMetricName(reqSzMetricName string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.RequestSizeMetricName = reqSzMetricName
+	}
+}
+
+// ResponseSizeMetricName is an option allowing to set the response size metric name.
+func ResponseSizeMetricName(resDurMetricName string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.ResponseSizeMetricName = resDurMetricName
+	}
+}
+
+// Engine is an option allowing to set the gin engine when intializing with New.
+// Example:
+// r := gin.Default()
+// p := ginprom.New(Engine(r))
+func Engine(e *gin.Engine) PrometheusOption {
+	return func(p *Prometheus) {
+		p.Engine = e
+	}
+}
+
+// Registry is an option allowing to set a  *prometheus.Registry with New.
+// Use this option if you want to use a custom Registry instead of a global one that prometheus
+// client uses by default
+// Example:
+// r := gin.Default()
+// p := ginprom.New(Registry(r))
+func Registry(r *prometheus.Registry) PrometheusOption {
+	return func(p *Prometheus) {
+		p.Registry = r
+	}
+}
+
+// HandlerNameFunc is an option allowing to set the HandlerNameFunc with New.
+// Use this option if you want to override the default behavior (i.e. using
+// (*gin.Context).HandlerName). This is useful when wanting to group different
+// functions under the same "handler" label or when using gin with decorated handlers
+// Example:
+// r := gin.Default()
+// p := ginprom.New(HandlerNameFunc(func (c *gin.Context) string { return "my handler" }))
+func HandlerNameFunc(f func(c *gin.Context) string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.HandlerNameFunc = f
+	}
+}
+
+// RequestPathFunc is an option allowing to set the RequestPathFunc with New.
+// Use this option if you want to override the default behavior (i.e. using
+// (*gin.Context).FullPath). This is useful when wanting to group different requests
+// under the same "path" label or when wanting to process unknown routes (the default
+// (*gin.Context).FullPath return an empty string for unregistered routes). Note that
+// requests for which f returns the empty string are ignored.
+// To specifically ignore certain paths, see the Ignore option.
+// Example:
+//
+//	r := gin.Default()
+//	p := ginprom.New(RequestPathFunc(func (c *gin.Context) string {
+//		if fullpath := c.FullPath(); fullpath != "" {
+//			return fullpath
+//		}
+//		return "<unknown>"
+//	}))
+func RequestPathFunc(f func(c *gin.Context) string) PrometheusOption {
+	return func(p *Prometheus) {
+		p.RequestPathFunc = f
+	}
+}

prom.go

@@ -203,147 +203,11 @@ func (p *Prometheus) mustRegister(c ...prometheus.Collector) {
 	registerer.MustRegister(c...)
 }
 
-// Path is an option allowing to set the metrics path when initializing with New.
-func Path(path string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.MetricsPath = path
-	}
-}
-
-// Ignore is used to disable instrumentation on some routes.
-func Ignore(paths ...string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.Ignored.Lock()
-		defer p.Ignored.Unlock()
-		for _, path := range paths {
-			p.Ignored.values[path] = true
-		}
-	}
-}
-
-// BucketSize is used to define the default bucket size when initializing with
-// New.
-func BucketSize(b []float64) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.BucketsSize = b
-	}
-}
-
-// Subsystem is an option allowing to set the subsystem when initializing
-// with New.
-func Subsystem(sub string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.Subsystem = sub
-	}
-}
-
-// Namespace is an option allowing to set the namespace when initializing
-// with New.
-func Namespace(ns string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.Namespace = ns
-	}
-}
-
-// Token is an option allowing to set the bearer token in prometheus
-// with New.
-// Example: ginprom.New(ginprom.Token("your_custom_token"))
-func Token(token string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.Token = token
-	}
-}
-
-// RequestCounterMetricName is an option allowing to set the request counter metric name.
-func RequestCounterMetricName(reqCntMetricName string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.RequestCounterMetricName = reqCntMetricName
-	}
-}
-
-// RequestDurationMetricName is an option allowing to set the request duration metric name.
-func RequestDurationMetricName(reqDurMetricName string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.RequestDurationMetricName = reqDurMetricName
-	}
-}
-
-// RequestSizeMetricName is an option allowing to set the request size metric name.
-func RequestSizeMetricName(reqSzMetricName string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.RequestSizeMetricName = reqSzMetricName
-	}
-}
-
-// ResponseSizeMetricName is an option allowing to set the response size metric name.
-func ResponseSizeMetricName(resDurMetricName string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.ResponseSizeMetricName = resDurMetricName
-	}
-}
-
-// Engine is an option allowing to set the gin engine when intializing with New.
-// Example:
-// r := gin.Default()
-// p := ginprom.New(Engine(r))
-func Engine(e *gin.Engine) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.Engine = e
-	}
-}
-
-// Registry is an option allowing to set a  *prometheus.Registry with New.
-// Use this option if you want to use a custom Registry instead of a global one that prometheus
-// client uses by default
-// Example:
-// r := gin.Default()
-// p := ginprom.New(Registry(r))
-func Registry(r *prometheus.Registry) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.Registry = r
-	}
-}
-
-// HandlerNameFunc is an option allowing to set the HandlerNameFunc with New.
-// Use this option if you want to override the default behavior (i.e. using
-// (*gin.Context).HandlerName). This is useful when wanting to group different
-// functions under the same "handler" label or when using gin with decorated handlers
-// Example:
-// r := gin.Default()
-// p := ginprom.New(HandlerNameFunc(func (c *gin.Context) string { return "my handler" }))
-func HandlerNameFunc(f func(c *gin.Context) string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.HandlerNameFunc = f
-	}
-}
-
-// RequestPathFunc is an option allowing to set the RequestPathFunc with New.
-// Use this option if you want to override the default behavior (i.e. using
-// (*gin.Context).FullPath). This is useful when wanting to group different requests
-// under the same "path" label or when wanting to process unknown routes (the default
-// (*gin.Context).FullPath return an empty string for unregistered routes). Note that
-// requests for which f returns the empty string are ignored.
-// To specifically ignore certain paths, see the Ignore option.
-// Example:
-//
-//	r := gin.Default()
-//	p := ginprom.New(RequestPathFunc(func (c *gin.Context) string {
-//		if fullpath := c.FullPath(); fullpath != "" {
-//			return fullpath
-//		}
-//		return "<unknown>"
-//	}))
-func RequestPathFunc(f func(c *gin.Context) string) func(*Prometheus) {
-	return func(p *Prometheus) {
-		p.RequestPathFunc = f
-	}
-}
-
 // New will initialize a new Prometheus instance with the given options.
 // If no options are passed, sane defaults are used.
 // If a router is passed using the Engine() option, this instance will
 // automatically bind to it.
-func New(options ...func(*Prometheus)) *Prometheus {
+func New(options ...PrometheusOption) *Prometheus {
 	p := &Prometheus{
 		MetricsPath:               defaultPath,
 		Namespace:                 defaultNs,

prom_test.go

@@ -409,6 +409,23 @@ func TestMetricsBearerToken(t *testing.T) {
 	unregister(p)
 }
 
+func TestCustomCounterErr(t *testing.T) {
+	p := New()
+	assert.Equal(t, p.IncrementCounterValue("not_found", []string{"some", "labels"}), ErrCustomCounter)
+	assert.Equal(t, p.AddCounterValue("not_found", []string{"some", "labels"}, 1.), ErrCustomCounter)
+	unregister(p)
+}
+
+func TestCustomGaugeErr(t *testing.T) {
+	p := New()
+	assert.Equal(t, p.IncrementGaugeValue("not_found", []string{"some", "labels"}), ErrCustomGauge)
+	assert.Equal(t, p.DecrementGaugeValue("not_found", []string{"some", "labels"}), ErrCustomGauge)
+	assert.Equal(t, p.AddGaugeValue("not_found", []string{"some", "labels"}, 1.), ErrCustomGauge)
+	assert.Equal(t, p.SubGaugeValue("not_found", []string{"some", "labels"}, 1.), ErrCustomGauge)
+	assert.Equal(t, p.SetGaugeValue("not_found", []string{"some", "labels"}, 1.), ErrCustomGauge)
+	unregister(p)
+}
+
 func TestInstrumentCustomCounter(t *testing.T) {
 	var helpText = "help text"
 	var labels = []string{"label1"}