Add XDG support for siegfried home directory (#221)

* add support for XDG and allow overriding siegfried home via environment variable

Uses github.com/adrg/xdg for mapping the right data directory per platform.
This means, unless a siegfried home directory already exists for the current user,
it will now be created in:

Linux: "~/$XDG_DATA_HOME/siegfried" (or "~/.local/share/siegfried")
macOS: "~/Library/Application Support/siegfried"
Windows: "%LOCALAPPDATA%"

* move away from deprecated ioutil package and use newer error type checking method

* use local implementation for finding the user data directory per platform

* add missing windows import

* fix wrong variable scope for Windows path initialization

cmd/sf/conf.go

@@ -17,8 +17,10 @@ package main
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"flag"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"strings"
@@ -59,7 +61,7 @@ func setconf() (string, error) {
 	}
 	// no flags - so we delete the conf file if it exists
 	if _, err := os.Stat(config.Conf()); err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) {
 			return "", nil
 		}
 		return "", err
@@ -70,7 +72,7 @@ func setconf() (string, error) {
 // if it exists, read defaults from the conf file.
 func getconf() (map[string]string, error) {
 	if _, err := os.Stat(config.Conf()); err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) {
 			return nil, nil
 		}
 		return nil, err

cmd/sf/update.go

@@ -20,7 +20,9 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"net/http"
 	"os"
@@ -118,7 +120,7 @@ func updateSigs(sig string, args []string) (bool, string, error) {
 	}
 	// this hairy bit of golang exception handling is thanks to Ross! :)
 	if _, err = os.Stat(config.Home()); err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, fs.ErrNotExist) {
 			err = os.MkdirAll(config.Home(), os.ModePerm)
 			if err != nil {
 				return false, "", fmt.Errorf("Siegfried: cannot create home directory %s, %v", config.Home(), err)

pkg/config/default.go

@@ -1,3 +1,4 @@
+//go:build !brew && !archivematica && !js
 // +build !brew,!archivematica,!js
 
 // Copyright 2014 Richard Lehane. All rights reserved.
@@ -17,16 +18,53 @@
 package config
 
 import (
+	"errors"
+	"io/fs"
 	"log"
-	"os/user"
+	"os"
 	"path/filepath"
+	"strings"
 )
 
-// the default Home location is a "siegfried" folder in the user's $HOME
+// the default Home location is a "siegfried" folder in the user's application data folder, which can be overridden by setting the SIEGFRIED_HOME environment variable
 func init() {
-	current, err := user.Current()
-	if err != nil {
-		log.Fatal(err)
+	if home, ok := os.LookupEnv("SIEGFRIED_HOME"); ok {
+		siegfried.home = home
+	} else {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		// if a home directory already exists in the legacy location continue using it, otherwise default to a XDG-aware OS-specific application data directory
+		siegfried.home = filepath.Join(home, "siegfried")
+		if _, err := os.Stat(siegfried.home); err != nil {
+			if errors.Is(err, fs.ErrNotExist) {
+				siegfried.home = filepath.Join(userDataDir(home), "siegfried")
+			} else {
+				log.Fatal(err)
+			}
+		}
+	}
+}
+
+func xdgPath(home string, defaultPath string) string {
+	dataHome, found := os.LookupEnv("XDG_DATA_HOME")
+	if found && dataHome != "" {
+		if dataDir, found := strings.CutPrefix(dataHome, "~"); found {
+			dataHome = filepath.Join(home, dataDir)
+		}
+
+		// environment variable might contain variables like $HOME itself, let's expand
+		dataHome = os.ExpandEnv(dataHome)
+	}
+
+	// XDG Base Directory Specification demands relative paths to be ignored, fall back to default in that case
+	if filepath.IsAbs(dataHome) {
+		return dataHome
+	} else if filepath.IsAbs(defaultPath) {
+		return defaultPath
+	} else {
+		return filepath.Join(home, defaultPath)
 	}
-	siegfried.home = filepath.Join(current.HomeDir, "siegfried")
 }

pkg/config/default_darwin.go

@@ -0,0 +1,27 @@
+//go:build darwin && !brew && !archivematica && !js
+// +build darwin,!brew,!archivematica,!js
+
+// Copyright 2014 Richard Lehane. All rights reserved.
+//
+// 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 config
+
+import (
+	"path/filepath"
+)
+
+
+func userDataDir(home string) string {
+	return xdgPath(home, filepath.Join("Library", "Application Support"))
+}

pkg/config/default_plan9.go

@@ -0,0 +1,23 @@
+//go:build plan9 && !brew && !archivematica && !js
+// +build plan9,!brew,!archivematica,!js
+
+// Copyright 2014 Richard Lehane. All rights reserved.
+//
+// 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 config
+
+
+func userDataDir(home string) string {
+	return xdgPath(home, "lib")
+}

pkg/config/default_unix.go

@@ -0,0 +1,26 @@
+//go:build (aix || darwin || dragonfly || freebsd || nacl || linux || netbsd || openbsd || solaris) && !brew && !archivematica && !js
+// +build aix darwin dragonfly freebsd nacl linux netbsd openbsd solaris
+// +build !brew
+// +build !archivematica
+// +build !js
+
+// Copyright 2014 Richard Lehane. All rights reserved.
+//
+// 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 config
+
+
+func userDataDir(home string) string {
+	return xdgPath(home, ".local/share")
+}

pkg/config/default_windows.go

@@ -0,0 +1,44 @@
+//go:build windows && !brew && !archivematica && !js
+// +build windows,!brew,!archivematica,!js
+
+// Copyright 2014 Richard Lehane. All rights reserved.
+//
+// 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 config
+
+import (
+	"os"
+	"path/filepath"
+
+	"golang.org/x/sys/windows"
+)
+
+
+func userDataDir(home string) string {
+	path, _ := windows.KnownFolderPath(*windows.FOLDERID_LocalAppData, windows.KF_FLAG_DEFAULT|KF_FLAG_DONT_VERIFY)
+	if path == "" {
+		path, _ = windows.KnownFolderPath(*windows.FOLDERID_LocalAppData, windows.KF_FLAG_DEFAULT_PATH|KF_FLAG_DONT_VERIFY)
+	}
+
+	if path == "" {
+		dataDir, found := os.LookupEnv("LOCALAPPDATA")
+		if found && dataDir != "" {
+			path = dataDir
+		} else {
+			path = filepath.Join("AppData", "Local")
+		}
+	}
+
+	return xdgPath(home, path)
+}

pkg/config/mimeinfo.go

@@ -16,7 +16,7 @@ package config
 
 import (
 	"encoding/json"
-	"io/ioutil"
+	"os"
 	"path/filepath"
 )
 
@@ -49,7 +49,7 @@ func MIMEInfo() string {
 }
 
 func MIMEVersion() []string {
-	byt, err := ioutil.ReadFile(filepath.Join(siegfried.home, mimeinfo.versions))
+	byt, err := os.ReadFile(filepath.Join(siegfried.home, mimeinfo.versions))
 	m := make(map[string][]string)
 	if err == nil {
 		err = json.Unmarshal(byt, &m)

pkg/config/pronom.go

@@ -16,8 +16,8 @@ package config
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net/http"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -125,7 +125,7 @@ func ContainerBase() string {
 func latest(prefix, suffix string) (string, error) {
 	var hits []string
 	var ids []int
-	files, err := ioutil.ReadDir(siegfried.home)
+	files, err := os.ReadDir(siegfried.home)
 	if err != nil {
 		return "", err
 	}
@@ -141,7 +141,7 @@ func latest(prefix, suffix string) (string, error) {
 		}
 	}
 	if len(hits) == 0 {
-		return "", fmt.Errorf("Config: no file in %s with prefix %s", siegfried.home, prefix)
+		return "", fmt.Errorf("config: no file in %s with prefix %s", siegfried.home, prefix)
 	}
 	if len(hits) == 1 {
 		return hits[0], nil

pkg/config/wikidata.go

@@ -18,7 +18,9 @@
 package config
 
 import (
+	"errors"
 	"fmt"
+	"io/fs"
 	"net/url"
 	"os"
 	"path/filepath"
@@ -324,7 +326,7 @@ func SetWikibaseSparql(query string) func() private {
 func checkWikibaseURL(customEndpointURL string, customWikibaseURL string) error {
 	if customWikibaseURL == WikidataWikibaseURL() {
 		return fmt.Errorf(
-			"Wikibase server URL for '%s' needs to be configured, can't be: '%s'",
+			"wikibase server URL for '%s' needs to be configured, can't be: '%s'",
 			customEndpointURL,
 			customWikibaseURL,
 		)
@@ -355,17 +357,18 @@ func SetCustomWikibaseEndpoint(customEndpointURL string, customWikibaseURL strin
 func SetCustomWikibaseQuery() error {
 	wikibaseSparqlPath := WikibaseSparqlFile()
 	sparqlFile, err := os.ReadFile(wikibaseSparqlPath)
-	if os.IsNotExist(err) {
-		return fmt.Errorf(
-			"Setting custom Wikibase SPARQL: cannot find file '%s' in '%s': %w",
-			wikibaseSparqlPath,
-			WikidataHome(),
-			err,
-		)
-	}
 	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return fmt.Errorf(
+				"setting custom Wikibase SPARQL: cannot find file '%s' in '%s': %w",
+				wikibaseSparqlPath,
+				WikidataHome(),
+				err,
+			)
+		}
+
 		return fmt.Errorf(
-			"Setting custom Wikibase SPARQL: unexpected error opening '%s' has occurred: %w",
+			"setting custom Wikibase SPARQL: unexpected error opening '%s' has occurred: %w",
 			wikibaseSparqlPath,
 			err,
 		)

pkg/config/wikidata_test.go

@@ -3,7 +3,6 @@ package config
 import (
 	"errors"
 	"io/fs"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -42,15 +41,17 @@ func TestProps(t *testing.T) {
 // handling required for updating our SPARQL query for a custom Wikibase.
 func TestSetCustomWikibaseQuery(t *testing.T) {
 	var testSPARQL = "select ?s ?p ?o where { ?s ?p ?o. }"
-	tempDir, _ := ioutil.TempDir("", "wikidata-test-dir-*")
-	defer os.RemoveAll(tempDir)
-	err := os.Mkdir(filepath.Join(tempDir, "wikidata"), 0755)
+	tempDir, err := os.MkdirTemp("", "wikidata-test-dir-*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.Mkdir(filepath.Join(tempDir, "wikidata"), 0755)
 	if err != nil {
 		t.Fatal(err)
 	}
 	SetHome(tempDir)
 	customSPARQLFile := filepath.Join(tempDir, "wikidata", "wikibase.sparql")
-	err = ioutil.WriteFile(customSPARQLFile, []byte(testSPARQL), 0755)
+	err = os.WriteFile(customSPARQLFile, []byte(testSPARQL), 0755)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -67,7 +68,7 @@ func TestSetCustomWikibaseQuery(t *testing.T) {
 			WikidataSPARQL(),
 		)
 	}
-	err = os.Remove(customSPARQLFile)
+	_ = os.Remove(customSPARQLFile)
 	err = SetCustomWikibaseQuery()
 	if !errors.Is(err, fs.ErrNotExist) {
 		t.Errorf(