Merge pull request #56029 from wackxu/errmsg

Automatic merge from submit-queue (batch tested with PRs 55112, 56029, 55740, 56095, 55845). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Improve kubeadm upgrade apply  error logging style

**What this PR does / why we need it**:

Improve kubeadm upgrade apply  error logging style

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes # https://github.com/kubernetes/kubeadm/issues/549

**Special notes for your reviewer**:

/assign @luxas 

**Release note**:

```release-note
NONE
```

cmd/kubeadm/app/cmd/upgrade/apply.go

@@ -202,16 +202,16 @@ func EnforceVersionPolicies(flags *applyFlags, versionGetter upgrade.VersionGett
 	if versionSkewErrs != nil {
 
 		if len(versionSkewErrs.Mandatory) > 0 {
-			return fmt.Errorf("The --version argument is invalid due to these fatal errors: %v", versionSkewErrs.Mandatory)
+			return fmt.Errorf("The --version argument is invalid due to these fatal errors:\n\n%v\nPlease fix the misalignments highlighted above and try upgrading again", kubeadmutil.FormatErrMsg(versionSkewErrs.Mandatory))
 		}
 
 		if len(versionSkewErrs.Skippable) > 0 {
 			// Return the error if the user hasn't specified the --force flag
 			if !flags.force {
-				return fmt.Errorf("The --version argument is invalid due to these errors: %v. Can be bypassed if you pass the --force flag", versionSkewErrs.Skippable)
+				return fmt.Errorf("The --version argument is invalid due to these errors:\n\n%v\nCan be bypassed if you pass the --force flag", kubeadmutil.FormatErrMsg(versionSkewErrs.Skippable))
 			}
 			// Soft errors found, but --force was specified
-			fmt.Printf("[upgrade/version] Found %d potential version compatibility errors but skipping since the --force flag is set: %v\n", len(versionSkewErrs.Skippable), versionSkewErrs.Skippable)
+			fmt.Printf("[upgrade/version] Found %d potential version compatibility errors but skipping since the --force flag is set: \n\n%v", len(versionSkewErrs.Skippable), kubeadmutil.FormatErrMsg(versionSkewErrs.Skippable))
 		}
 	}
 	return nil

cmd/kubeadm/app/util/error.go

@@ -75,3 +75,12 @@ func checkErr(prefix string, err error, handleErr func(string, int)) {
 		handleErr(err.Error(), DefaultErrorExitCode)
 	}
 }
+
+// FormatErrMsg returns a human-readable string describing the slice of errors passed to the function
+func FormatErrMsg(errs []error) string {
+	var errMsg string
+	for _, err := range errs {
+		errMsg = fmt.Sprintf("%s\t-%s\n", errMsg, err.Error())
+	}
+	return errMsg
+}

cmd/kubeadm/app/util/error_test.go

@@ -50,3 +50,34 @@ func TestCheckErr(t *testing.T) {
 		}
 	}
 }
+
+func TestFormatErrMsg(t *testing.T) {
+	errMsg1 := "specified version to upgrade to v1.9.0-alpha.3 is equal to or lower than the cluster version v1.10.0-alpha.0.69+638add6ddfb6d2. Downgrades are not supported yet"
+	errMsg2 := "specified version to upgrade to v1.9.0-alpha.3 is higher than the kubeadm version v1.9.0-alpha.1.3121+84178212527295-dirty. Upgrade kubeadm first using the tool you used to install kubeadm"
+
+	testCases := []struct {
+		errs   []error
+		expect string
+	}{
+		{
+			errs: []error{
+				fmt.Errorf(errMsg1),
+				fmt.Errorf(errMsg2),
+			},
+			expect: "\t-" + errMsg1 + "\n" + "\t-" + errMsg2 + "\n",
+		},
+		{
+			errs: []error{
+				fmt.Errorf(errMsg1),
+			},
+			expect: "\t-" + errMsg1 + "\n",
+		},
+	}
+
+	for _, testCase := range testCases {
+		got := FormatErrMsg(testCase.errs)
+		if got != testCase.expect {
+			t.Errorf("FormatErrMsg error, expect: %v, got: %v", testCase.expect, got)
+		}
+	}
+}