From 15e42574d2b4ca5ab3b79a61e26f029d9f3815cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20M=C3=ADchal?= <harrymichal@seznam.cz>
Date: Mon, 7 Jun 2021 14:11:27 +0200
Subject: [PATCH] pkg/podman: Add error parsing method

This new helper type serves for parsing the output of Podman in stderr
into a form that can be further analyzed.

The most significant part is the method Is() that lexically compares
error strings. This is needed because there are no defined errors to
catch errors coming from Podman.

https://github.com/containers/toolbox/pull/786
---
 src/pkg/podman/error.go | 113 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 src/pkg/podman/error.go

diff --git a/src/pkg/podman/error.go b/src/pkg/podman/error.go
new file mode 100644
index 000000000..0aa68c5d2
--- /dev/null
+++ b/src/pkg/podman/error.go
@@ -0,0 +1,113 @@
+/*
+ * Copyright © 2019 – 2021 Red Hat Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package podman
+
+import (
+	"bytes"
+	"strings"
+)
+
+// internalError serves for representing errors printed by Podman to stderr
+type internalError struct {
+	errors []string
+}
+
+func (e *internalError) Error() string {
+	if e.errors == nil || len(e.errors) == 0 {
+		return ""
+	}
+
+	var builder strings.Builder
+	for i, part := range e.errors {
+		if i != 0 {
+			builder.WriteString(": ")
+		}
+		builder.WriteString(part)
+	}
+	return builder.String()
+}
+
+// Is lexically compares errors
+//
+// The comparison is done for every part in the error chain not across.
+func (e *internalError) Is(target error) bool {
+	if target == nil {
+		return false
+	}
+
+	if e.errors == nil || len(e.errors) == 0 {
+		return false
+	}
+
+	for {
+		if e.errors[0] == target.Error() {
+			return true
+		}
+
+		err := e.Unwrap()
+		if err == nil {
+			return false
+		}
+		e = err.(*internalError)
+	}
+}
+
+func (e internalError) Unwrap() error {
+	if e.errors == nil || len(e.errors) <= 1 {
+		return nil
+	}
+
+	return &internalError{e.errors[1:]}
+}
+
+// parseErrorMsg serves for converting error output of Podman into an error
+// that can be further used in Go
+func parseErrorMsg(stderr *bytes.Buffer) error {
+	errMsg := stderr.String()
+	errMsg = strings.TrimSpace(errMsg)
+	if errMsg == "" {
+		return nil
+	}
+
+	// Stderr is not used only for error messages but also for e.g. loading
+	// bars
+	errMsgSplit := strings.SplitN(errMsg, "Error: ", 2)
+	// We're only interested in the part with an error
+	errMsg = errMsgSplit[len(errMsgSplit)-1]
+	// Sometimes an error contains a newline (e.g., responses from Docker
+	// registry). Normalize them into further parseable error message.
+	errMsg = strings.ReplaceAll(errMsg, "\n", ": ")
+	// Wrapped error messages are usually separated by a colon followed by
+	// a single space character
+	errMsgPartsRaw := strings.Split(errMsg, ": ")
+	// The parts of the err message still can have a whitespace at the
+	// beginning ar at the end. Trim them.
+	var errMsgParts []string
+	for _, part := range errMsgPartsRaw {
+		part = strings.TrimSpace(part)
+		// Podman error messages are usually prepended with the "Error: " string
+		// Sometimes the error contains errors in a bullet list. This list is
+		// usually prepended with a message equal to "errors:"
+		if part == "Error" || part == "errors:" {
+			continue
+		}
+
+		errMsgParts = append(errMsgParts, part)
+	}
+
+	return &internalError{errMsgParts}
+}