validate commit SHA to avoid common problem

internal/infra/run.go

@@ -13,6 +13,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"regexp"
 	"strings"
 	"syscall"
 	"time"
@@ -62,7 +63,23 @@ type RunParams struct {
 	InputRaw  []byte
 }
 
+var gitShaRegex = regexp.MustCompile(`^[0-9a-f]{40}$`)
+
+func (p *RunParams) Validate() error {
+	if p.Job == nil {
+		return fmt.Errorf("job is required")
+	}
+	if p.Job.Source.Commit != nil && *p.Job.Source.Commit != "" && !gitShaRegex.MatchString(*p.Job.Source.Commit) {
+		return fmt.Errorf("commit must be a SHA, or not provided")
+	}
+	return nil
+}
+
 func Run(params RunParams) error {
+	if err := params.Validate(); err != nil {
+		return err
+	}
+
 	var ctx context.Context
 	var cancel func()
 	if params.Timeout > 0 {

testdata/invalid-commit.yml

@@ -0,0 +1,10 @@
+job:
+  package-manager: go_modules
+  allowed-updates:
+    - dependency-type: direct
+      update-type: all
+  source:
+    provider: github
+    repo: rsc/quote
+    directory: /
+    commit: unknown

testdata/valid-commit.yml

@@ -0,0 +1,10 @@
+job:
+  package-manager: go_modules
+  allowed-updates:
+    - dependency-type: direct
+      update-type: all
+  source:
+    provider: github
+    repo: rsc/quote
+    directory: /
+    commit: 5d9f230bcfbae514bb6c2215694c2ce7273fc604

tests/integration_test.go

@@ -0,0 +1,49 @@
+package tests
+
+import (
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestIntegration(t *testing.T) {
+	// build the binary for the rest of the tests
+	_, filename, _, _ := runtime.Caller(0)
+	testPath := filepath.Dir(filename)
+	cliMain := path.Join(testPath, "../cmd/dependabot/dependabot.go")
+
+	if data, err := exec.Command("go", "build", cliMain).CombinedOutput(); err != nil {
+		t.Fatal("Failed to build the binary: ", string(data))
+	}
+	defer func() {
+		_ = os.Remove("dependabot")
+	}()
+
+	// Helper to run dependabot in the right directory
+	dependabot := func(args ...string) (string, error) {
+		cmd := exec.Command("./dependabot", args...)
+		cmd.Dir = testPath
+		output, err := cmd.CombinedOutput()
+		return string(output), err
+	}
+
+	t.Run("works with valid commits", func(t *testing.T) {
+		if output, err := dependabot("update", "-f", "../testdata/valid-commit.yml"); err != nil {
+			t.Fatal("Expected no error, but got: ", output)
+		}
+	})
+
+	t.Run("rejects invalid commits", func(t *testing.T) {
+		output, err := dependabot("update", "-f", "../testdata/invalid-commit.yml")
+		if err == nil {
+			t.Fatal("Expected an error, but got none")
+		}
+		if !strings.Contains(output, "commit must be a SHA, or not provided") {
+			t.Fatalf("Expected error message to mention bad commit, but got: \n%s", output)
+		}
+	})
+}