Portable plugin executable check for Windows platform (#367)

* Portable plugin executable check for Windows platform

 builds Windows and non-Windows platform plugin verifier separately

* Removes redundant build tag and file suffix, uses file suffix

  As we'll need either to mention, which file compiles for which
  platform.

pkg/kn/commands/plugin/plugin_verifier.go

@@ -1,4 +1,4 @@
-// Copyright © 2018 The Knative Authors
+// Copyright © 2019 The Knative Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,6 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build !windows
+
+// This file doesn't compile for Windows platform, it defines respective build tag (build tag),
+// the respective functionality is present in plugin_verifier_windows.go file in same dir,
+// which only compiles for Windows platform.
+
 package plugin
 
 import (

pkg/kn/commands/plugin/plugin_verifier_windows.go

@@ -0,0 +1,191 @@
+// Copyright © 2019 The Knative Authors
+//
+// 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.
+
+// This file is replacement of plugin_verifier.go file in same dir, and
+// compiles only for Windows platform (its suffix defines that).
+
+package plugin
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+)
+
+// pluginVerifier verifies that existing kn commands are not overriden
+type pluginVerifier struct {
+	root        *cobra.Command
+	seenPlugins map[string]string
+}
+
+// collect errors and warnings on the way
+type errorsAndWarnings struct {
+	errors   []string
+	warnings []string
+}
+
+// Create new verifier
+func newPluginVerifier(root *cobra.Command) *pluginVerifier {
+	return &pluginVerifier{
+		root:        root,
+		seenPlugins: make(map[string]string),
+	}
+}
+
+// permission bits for execute
+const (
+	UserExecute  = 1 << 6
+	GroupExecute = 1 << 3
+	OtherExecute = 1 << 0
+)
+
+// Verify implements pathVerifier and determines if a given path
+// is valid depending on whether or not it overwrites an existing
+// kn command path, or a previously seen plugin.
+// This method is not idempotent and must be called for each path only once.
+func (v *pluginVerifier) verify(eaw errorsAndWarnings, path string) errorsAndWarnings {
+	if v.root == nil {
+		return eaw.addError("unable to verify path with nil root")
+	}
+
+	// Verify that plugin actually exists
+	fileInfo, err := os.Stat(path)
+	if err != nil {
+		if err == os.ErrNotExist {
+			return eaw.addError("cannot find plugin in %s", path)
+		}
+		return eaw.addError("cannot stat %s: %v", path, err)
+	}
+
+	eaw = v.addErrorIfWrongPrefix(eaw, path)
+	eaw = v.addWarningIfNotExecutable(eaw, path, fileInfo)
+	eaw = v.addWarningIfAlreadySeen(eaw, path)
+	eaw = v.addErrorIfOverwritingExistingCommand(eaw, path)
+
+	// Remember each verified plugin for duplicate check
+	v.seenPlugins[filepath.Base(path)] = path
+
+	return eaw
+}
+
+func (v *pluginVerifier) addWarningIfAlreadySeen(eaw errorsAndWarnings, path string) errorsAndWarnings {
+	fileName := filepath.Base(path)
+	if existingPath, ok := v.seenPlugins[fileName]; ok {
+		return eaw.addWarning("%s is ignored because it is shadowed by a equally named plugin: %s.", path, existingPath)
+	}
+	return eaw
+}
+
+func (v *pluginVerifier) addErrorIfOverwritingExistingCommand(eaw errorsAndWarnings, path string) errorsAndWarnings {
+	fileName := filepath.Base(path)
+	cmds := strings.Split(fileName, "-")
+	if len(cmds) < 2 {
+		return eaw.addError("%s is not a valid plugin filename as its missing a prefix", fileName)
+	}
+	cmds = cmds[1:]
+
+	// Check both, commands with underscore and with dash because plugins can be called with both
+	overwrittenCommands := make(map[string]bool)
+	for _, c := range [][]string{cmds, convertUnderscoresToDashes(cmds)} {
+		cmd, _, err := v.root.Find(c)
+		if err == nil {
+			overwrittenCommands[cmd.CommandPath()] = true
+		}
+	}
+	for command := range overwrittenCommands {
+		eaw.addError("%s overwrites existing built-in command: %s", fileName, command)
+	}
+	return eaw
+}
+
+func (v *pluginVerifier) addErrorIfWrongPrefix(eaw errorsAndWarnings, path string) errorsAndWarnings {
+	fileName := filepath.Base(path)
+	// Only pick the first prefix as it is very like that it will be reduced to
+	// a single prefix anyway (PR pending)
+	prefix := ValidPluginFilenamePrefixes[0]
+	if !strings.HasPrefix(fileName, prefix+"-") {
+		eaw.addWarning("%s plugin doesn't start with plugin prefix %s", fileName, prefix)
+	}
+	return eaw
+}
+
+func (v *pluginVerifier) addWarningIfNotExecutable(eaw errorsAndWarnings, path string, fileInfo os.FileInfo) errorsAndWarnings {
+	if runtime.GOOS == "windows" {
+		return checkForWindowsExecutable(eaw, fileInfo, path)
+	}
+	return eaw
+}
+
+func checkForWindowsExecutable(eaw errorsAndWarnings, fileInfo os.FileInfo, path string) errorsAndWarnings {
+	fileExt := strings.ToLower(filepath.Ext(fileInfo.Name()))
+
+	switch fileExt {
+	case ".bat", ".cmd", ".com", ".exe", ".ps1":
+		return eaw
+	}
+	return eaw.addWarning("%s is not executable as it does not have the proper extension", path)
+}
+
+func (eaw *errorsAndWarnings) addError(format string, args ...interface{}) errorsAndWarnings {
+	eaw.errors = append(eaw.errors, fmt.Sprintf(format, args...))
+	return *eaw
+}
+
+func (eaw *errorsAndWarnings) addWarning(format string, args ...interface{}) errorsAndWarnings {
+	eaw.warnings = append(eaw.warnings, fmt.Sprintf(format, args...))
+	return *eaw
+}
+
+func (eaw *errorsAndWarnings) printWarningsAndErrors(out io.Writer) {
+	printSection(out, "ERROR", eaw.errors)
+	printSection(out, "WARNING", eaw.warnings)
+}
+
+func (eaw *errorsAndWarnings) combinedError() error {
+	if len(eaw.errors) == 0 {
+		return nil
+	}
+	return errors.New(strings.Join(eaw.errors, ","))
+}
+
+func printSection(out io.Writer, label string, values []string) {
+	if len(values) > 0 {
+		printLabelWithConditionalPluralS(out, label, len(values))
+		for _, value := range values {
+			fmt.Fprintf(out, "  - %s\n", value)
+		}
+	}
+}
+
+func printLabelWithConditionalPluralS(out io.Writer, label string, nr int) {
+	if nr == 1 {
+		fmt.Fprintf(out, "%s:\n", label)
+	} else {
+		fmt.Fprintf(out, "%ss:\n", label)
+	}
+}
+
+func convertUnderscoresToDashes(cmds []string) []string {
+	ret := make([]string, len(cmds))
+	for i := range cmds {
+		ret[i] = strings.ReplaceAll(cmds[i], "_", "-")
+	}
+	return ret
+}