Add command to check for swagger docs regeneration

magefile.go

@@ -21,8 +21,10 @@ package main
 import (
 	"bufio"
 	"bytes"
+	"crypto/sha256"
 	"fmt"
 	"github.com/magefile/mage/mg"
+	"io"
 	"os"
 	"os/exec"
 	"runtime"
@@ -188,6 +190,22 @@ func checkAndInstallGoTool(tool, importPath string) {
 	}
 }
 
+// Calculates a hash of a file
+func calculateHashOfFile(path string) (hash string, err error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%x", h.Sum(nil)), nil
+}
+
 // Cleans all build, executable and bindata files
 func Clean() error {
 	if err := exec.Command("go", "clean", "./...").Run(); err != nil {
@@ -262,8 +280,33 @@ func DoTheSwag() {
 	runAndStreamOutput("swag", "init", "-g", "./pkg/routes/routes.go", "--parseDependency", "-d", RootPath, "-o", RootPath+"/pkg/swagger")
 }
 
+// Checks if the swagger docs need to be re-generated from the code annotations
 func GotSwag() {
+	// The check is pretty cheaply done: We take the hash of the swagger.json file, generate the docs,
+	// hash the file again and compare the two hashes to see if anything changed. If that's the case,
+	// regenerating the docs is nessecary.
+	// swag is not capable of just outputting the generated docs to stdout, therefore we need to do it this way.
+	// Another drawback of this is obviously it will only work once - we're not resetting the newly generated
+	// docs after the check. This behaviour is good enough for ci though.
+	oldHash, err := calculateHashOfFile(RootPath + "/pkg/swagger/swagger.json")
+	if err != nil {
+		fmt.Printf("Error getting old hash of the swagger docs: %s", err)
+		os.Exit(1)
+	}
 
+	DoTheSwag()
+
+	newHash, err := calculateHashOfFile(RootPath + "/pkg/swagger/swagger.json")
+	if err != nil {
+		fmt.Printf("Error getting new hash of the swagger docs: %s", err)
+		os.Exit(1)
+	}
+
+	if oldHash != newHash {
+		fmt.Println("Swagger docs are not up to date.")
+		fmt.Println("Please run 'mage do-the-swag' and commit the result.")
+		os.Exit(1)
+	}
 }
 
 func MisspellCheck() {