feat: cache compiled regex

use mustcompile for regex.
Always use mustcompile which throws a panic
if the regex cannot be compiled.
We call recover to detect the panic and
display an error message to the user.

src/environment_windows_win32.go

@@ -4,7 +4,6 @@ package main
 
 import (
 	"fmt"
-	"regexp"
 	"strings"
 	"syscall"
 	"unsafe"
@@ -48,10 +47,8 @@ func getWindowTitle(imageName, windowTitleRegex string) (string, error) {
 	}
 
 	// returns the first window of the first pid
-	_, windowTitle, err := GetWindowTitle(processPid[0], windowTitleRegex)
-	if err != nil {
-		return "", nil
-	}
+	_, windowTitle := GetWindowTitle(processPid[0], windowTitleRegex)
+
 	return windowTitle, nil
 }
 
@@ -147,13 +144,10 @@ func GetWindowText(hwnd syscall.Handle, str *uint16, maxCount int32) (length int
 }
 
 // GetWindowTitle searches for a window attached to the pid
-func GetWindowTitle(pid int, windowTitleRegex string) (syscall.Handle, string, error) {
+func GetWindowTitle(pid int, windowTitleRegex string) (syscall.Handle, string) {
 	var hwnd syscall.Handle
 	var title string
-	compiledRegex, err := regexp.Compile(windowTitleRegex)
-	if err != nil {
-		return 0, "", fmt.Errorf("Error while compiling the regex '%s'", windowTitleRegex)
-	}
+
 	// callback fro EnumWindows
 	cb := syscall.NewCallback(func(h syscall.Handle, p uintptr) uintptr {
 		var prcsID int = 0
@@ -168,7 +162,7 @@ func GetWindowTitle(pid int, windowTitleRegex string) (syscall.Handle, string, e
 				return 1 // continue enumeration
 			}
 			title = syscall.UTF16ToString(b)
-			if compiledRegex.MatchString(title) {
+			if matchString(windowTitleRegex, title) {
 				// will cause EnumWindows to return 0 (error)
 				// but we don't want to enumerate all windows since we got what we want
 				hwnd = h
@@ -183,5 +177,5 @@ func GetWindowTitle(pid int, windowTitleRegex string) (syscall.Handle, string, e
 	// it returns 0(error occurred) instead of 1(success)
 	// In our case, title will equal "" or the title of the window anyway
 	_ = EnumWindows(cb, 0)
-	return hwnd, title, nil
+	return hwnd, title
 }

src/init/omp.ps1

@@ -45,7 +45,7 @@ function global:Set-PoshGitStatus {
     $config = $global:PoshSettings.Theme
     $cleanPWD = $PWD.ProviderPath.TrimEnd("\")
     $cleanPSWD = $PWD.ToString().TrimEnd("\")
-    $standardOut = @(&$omp --error="$errorCode" --pwd="$cleanPWD" --pswd="$cleanPSWD" --execution-time="$executionTime" --config="$config")
+    $standardOut = @(&$omp --error="$errorCode" --pwd="$cleanPWD" --pswd="$cleanPSWD" --execution-time="$executionTime" --config="$config" 2>&1)
     # Restore initial encoding
     [Console]::OutputEncoding = $originalOutputEncoding
     # the ouput can be multiline, joining these ensures proper rendering by adding line breaks with `n

src/regex.go

@@ -1,9 +1,36 @@
 package main
 
-import "regexp"
+import (
+	"regexp"
+	"sync"
+)
+
+var (
+	regexCache     map[string]*regexp.Regexp = make(map[string]*regexp.Regexp)
+	regexCacheLock                           = sync.Mutex{}
+)
+
+func getCompiledRegex(pattern string) *regexp.Regexp {
+	// try in cache first
+	re := regexCache[pattern]
+	if re != nil {
+		return re
+	}
+
+	// should we panic or return the error?
+	re = regexp.MustCompile(pattern)
+
+	// lock for concurrent access and save the compiled expression in cache
+	regexCacheLock.Lock()
+	regexCache[pattern] = re
+	regexCacheLock.Unlock()
+
+	return re
+}
 
 func findNamedRegexMatch(pattern, text string) map[string]string {
-	re := regexp.MustCompile(pattern)
+	// error ignored because mustCompile will cause a panic
+	re := getCompiledRegex(pattern)
 	match := re.FindStringSubmatch(text)
 	result := make(map[string]string)
 	if len(match) == 0 {
@@ -19,7 +46,7 @@ func findNamedRegexMatch(pattern, text string) map[string]string {
 }
 
 func findAllNamedRegexMatch(pattern, text string) []map[string]string {
-	re := regexp.MustCompile(pattern)
+	re := getCompiledRegex(pattern)
 	match := re.FindAllStringSubmatch(text, -1)
 	var results []map[string]string
 	if len(match) == 0 {
@@ -40,6 +67,11 @@ func findAllNamedRegexMatch(pattern, text string) []map[string]string {
 }
 
 func replaceAllString(pattern, text, replaceText string) string {
-	re := regexp.MustCompile(pattern)
+	re := getCompiledRegex(pattern)
 	return re.ReplaceAllString(text, replaceText)
 }
+
+func matchString(pattern, text string) bool {
+	re := getCompiledRegex(pattern)
+	return re.MatchString(text)
+}

src/segment.go

@@ -3,7 +3,6 @@ package main
 import (
 	"errors"
 	"fmt"
-	"regexp"
 )
 
 // Segment represent a single segment and it's configuration
@@ -112,10 +111,8 @@ func (segment *Segment) shouldIgnoreFolder(cwd string) bool {
 		list := parseStringArray(value)
 		for _, element := range list {
 			pattern := fmt.Sprintf("^%s$", element)
-			matched, err := regexp.MatchString(pattern, cwd)
-			if err == nil && matched {
-				return true
-			}
+			matched := matchString(pattern, cwd)
+			return matched
 		}
 		return false
 	}
@@ -163,6 +160,17 @@ func (segment *Segment) mapSegmentWithWriter(env environmentInfo) error {
 }
 
 func (segment *Segment) setStringValue(env environmentInfo, cwd string) {
+	defer func() {
+		err := recover()
+		if err == nil {
+			return
+		}
+		// display a message explaining omp failed(with the err)
+		message := fmt.Sprintf("oh-my-posh fatal error rendering %s segment:%s", segment.Type, err)
+		fmt.Println(message)
+		segment.stringValue = "error"
+		segment.active = true
+	}()
 	err := segment.mapSegmentWithWriter(env)
 	if err != nil || segment.shouldIgnoreFolder(cwd) {
 		return

src/segment_test.go

@@ -84,8 +84,14 @@ func TestShouldIgnoreFolderRegexInverted(t *testing.T) {
 			IgnoreFolders: []string{"(?!Projects[\\/]).*"},
 		},
 	}
-	got := segment.shouldIgnoreFolder(cwd)
-	assert.False(t, got)
+	// detect panic(thrown by MustCompile)
+	defer func() {
+		if err := recover(); err != nil {
+			// display a message explaining omp failed(with the err)
+			assert.Equal(t, "regexp: Compile(`^(?!Projects[\\/]).*$`): error parsing regexp: invalid or unsupported Perl syntax: `(?!`", err)
+		}
+	}()
+	segment.shouldIgnoreFolder(cwd)
 }
 
 func TestShouldIgnoreFolderRegexInvertedNonEscaped(t *testing.T) {
@@ -94,6 +100,12 @@ func TestShouldIgnoreFolderRegexInvertedNonEscaped(t *testing.T) {
 			IgnoreFolders: []string{"(?!Projects/).*"},
 		},
 	}
-	got := segment.shouldIgnoreFolder(cwd)
-	assert.False(t, got)
+	// detect panic(thrown by MustCompile)
+	defer func() {
+		if err := recover(); err != nil {
+			// display a message explaining omp failed(with the err)
+			assert.Equal(t, "regexp: Compile(`^(?!Projects/).*$`): error parsing regexp: invalid or unsupported Perl syntax: `(?!`", err)
+		}
+	}()
+	segment.shouldIgnoreFolder(cwd)
 }