Move URL checking code to dedicated function

Previously only used for a single library.properties function, multiple planned package index rules will need to do this
as well. So it is best to share the code between all of them.

Author: per1234

Diff for: internal/rule/rulefunction/library.go

@@ -19,7 +19,6 @@ package rulefunction
 
 import (
 	"fmt"
-	"net/http"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -1010,17 +1009,12 @@ func LibraryPropertiesUrlFieldDeadLink() (result ruleresult.Type, output string)
 		return ruleresult.NotRun, "Field not present"
 	}
 
-	logrus.Tracef("Checking URL: %s", url)
-	httpResponse, err := http.Head(url)
+	err := checkURL(url)
 	if err != nil {
 		return ruleresult.Fail, err.Error()
 	}
 
-	if httpResponse.StatusCode == http.StatusOK {
-		return ruleresult.Pass, ""
-	}
-
-	return ruleresult.Fail, httpResponse.Status
+	return ruleresult.Pass, ""
 }
 
 // LibraryPropertiesArchitecturesFieldMissing checks for missing library.properties "architectures" field.

Diff for: internal/rule/rulefunction/rulefunction.go

@@ -19,13 +19,15 @@ package rulefunction
 import (
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"regexp"
 	"strings"
 
 	"github.com/arduino/arduino-lint/internal/project/projectdata"
 	"github.com/arduino/arduino-lint/internal/project/sketch"
 	"github.com/arduino/arduino-lint/internal/rule/ruleresult"
 	"github.com/arduino/go-paths-helper"
+	"github.com/sirupsen/logrus"
 )
 
 // Type is the function signature for the rule functions.
@@ -156,3 +158,17 @@ func isValidJSON(path *paths.Path) bool {
 	}
 	return json.Valid(data)
 }
+
+func checkURL(url string) error {
+	logrus.Tracef("Checking URL: %s", url)
+	response, err := http.Head(url)
+	if err != nil {
+		return err
+	}
+
+	if response.StatusCode != http.StatusOK {
+		return fmt.Errorf("%s", response.Status)
+	}
+
+	return nil
+}