tooling: check for missing dependencies when building Fider (#593)

.circleci/config.yml

@@ -1,7 +1,7 @@
 version: 2
 references:
   builder: &builder 
-    getfider/circleci:0.0.14
+    getfider/circleci:0.0.15
   workdir: &workdir 
     /go/src/github.com/getfider/fider
 

magefile.go

@@ -3,14 +3,30 @@
 package main
 
 import (
+	"fmt"
 	"os"
+	"os/exec"
 	"runtime"
 	"time"
 
 	"github.com/magefile/mage/mg"
 	"github.com/magefile/mage/sh"
 )
 
+// warning shown when at least one dependency is not installed
+var missingDepsWarning = `Dependencies %v are missing. Please install them and try again.
+To learn how, visit our contributors guide: https://github.com/getfider/fider/blob/master/CONTRIBUTING.md.
+`
+
+// required dependencies for building fider
+var requiredDeps = []string{
+	"air",
+	"godotenv",
+	"docker",
+	"npm",
+	"node",
+	"mage",
+}
 var buildTime = time.Now().Format("2006.01.02.150405")
 var buildNumber = os.Getenv("CIRCLE_BUILD_NUM")
 var exeName = "fider"
@@ -26,6 +42,12 @@ func init() {
 	if runtime.GOOS == "windows" {
 		exeName = "fider.exe"
 	}
+
+	missingDeps := missingDependencies()
+	if len(missingDeps) > 0 {
+		fmt.Printf(missingDepsWarning, missingDeps)
+		os.Exit(1)
+	}
 }
 
 func Run() error {
@@ -116,3 +138,14 @@ func buildServer(env map[string]string) error {
 	ldflags := "-s -w -X main.buildtime=" + buildTime + " -X main.buildnumber=" + buildNumber
 	return sh.RunWith(env, "go", "build", "-ldflags", ldflags, "-o", exeName, ".")
 }
+
+func missingDependencies() []string {
+	var missingDeps []string
+	for _, dep := range requiredDeps {
+		_, err := exec.LookPath(dep)
+		if err != nil {
+			missingDeps = append(missingDeps, dep)
+		}
+	}
+	return missingDeps
+}