Check errors and enable errcheck in lint config

.golangci.yaml

@@ -1,7 +1,23 @@
 version: "2"
 linters:
-  disable:
-    - errcheck
+  settings:
+    errcheck:
+      exclude-functions:
+        - (*github.com/fsnotify/fsnotify.Watcher).Close
+        - (*net.TCPConn).CloseWrite
+        - (*net.UnixConn).CloseWrite
+        - (*os.File).Close
+        - (*os.File).Write
+        - (*text/tabwriter.Writer).Flush
+        - (io.Closer).Close
+        - (io.Writer).Write
+        - (net.Conn).Close
+        - (net.Listener).Close
+        - fmt.Fprintf
+        - fmt.Fprintln
+        - io.WriteString
+        - os.Setenv
+        - syscall.Close
 issues:
   max-issues-per-linter: 0  # no limit
   max-same-issues: 0        # no limit

app.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"cmp"
 	"errors"
 	"fmt"
 	"io"
@@ -129,7 +130,10 @@ func loadFiles() (clipboard clipboard, err error) {
 
 	s := bufio.NewScanner(files)
 
-	s.Scan()
+	if !s.Scan() {
+		err = fmt.Errorf("scanning file list: %w", cmp.Or(s.Err(), io.EOF))
+		return
+	}
 
 	switch s.Text() {
 	case "copy":
@@ -168,18 +172,23 @@ func saveFiles(clipboard clipboard) error {
 
 	log.Printf("saving files: %v", clipboard.paths)
 
+	var clipboardModeStr string
 	if clipboard.mode == clipboardCopy {
-		fmt.Fprintln(files, "copy")
+		clipboardModeStr = "copy"
 	} else {
-		fmt.Fprintln(files, "move")
+		clipboardModeStr = "move"
+	}
+	if _, err := fmt.Fprintln(files, clipboardModeStr); err != nil {
+		return fmt.Errorf("write clipboard mode to file: %w", err)
 	}
 
 	for _, path := range clipboard.paths {
-		fmt.Fprintln(files, path)
+		if _, err := fmt.Fprintln(files, path); err != nil {
+			return fmt.Errorf("write path to file: %w", err)
+		}
 	}
 
-	files.Sync()
-	return nil
+	return files.Sync()
 }
 
 func (app *app) readHistory() error {

client.go

@@ -128,7 +128,9 @@ func readExpr() <-chan expr {
 			c, err = net.Dial(gSocketProt, gSocketPath)
 		}
 
-		fmt.Fprintf(c, "conn %d\n", gClientID)
+		if _, err := fmt.Fprintf(c, "conn %d\n", gClientID); err != nil {
+			log.Fatalf("registering with server: %s", err)
+		}
 
 		ch <- &callExpr{"sync", nil, 1}
 		ch <- &callExpr{"on-init", nil, 1}
@@ -143,12 +145,11 @@ func readExpr() <-chan expr {
 			// running `$lf -remote "query $id <something>"`.
 			if word, rest := splitWord(s.Text()); word == "query" {
 				gState.mutex.Lock()
-				state, ok := gState.data[rest]
+				state := gState.data[rest]
 				gState.mutex.Unlock()
-				if ok {
-					fmt.Fprint(c, state)
+				if _, err := fmt.Fprintln(c, state); err != nil {
+					log.Fatalf("sending response to server: %s", err)
 				}
-				fmt.Fprintln(c, "")
 			} else {
 				p := newParser(strings.NewReader(s.Text()))
 				if p.parse() {
@@ -157,6 +158,10 @@ func readExpr() <-chan expr {
 			}
 		}
 
+		if err := s.Err(); err != nil {
+			log.Printf("reading from server: %s", err)
+		}
+
 		c.Close()
 	}()
 
@@ -169,17 +174,20 @@ func remote(cmd string) error {
 		return fmt.Errorf("dialing to send server: %w", err)
 	}
 
-	fmt.Fprintln(c, cmd)
+	if _, err := fmt.Fprintln(c, cmd); err != nil {
+		return fmt.Errorf("sending command to server: %w", err)
+	}
 
 	// XXX: Standard net.Conn interface does not include a CloseWrite method
 	// but net.UnixConn and net.TCPConn implement it so the following should be
 	// safe as long as we do not use other types of connections. We need
 	// CloseWrite to notify the server that this is not a persistent connection
 	// and it should be closed after the response.
-	if v, ok := c.(interface {
-		CloseWrite() error
-	}); ok {
-		v.CloseWrite()
+	switch c := c.(type) {
+	case *net.TCPConn:
+		c.CloseWrite()
+	case *net.UnixConn:
+		c.CloseWrite()
 	}
 
 	// The most straightforward way to write the response to stdout would be

copy.go

@@ -54,10 +54,11 @@ func copySize(srcs []string) (int64, error) {
 	return total, nil
 }
 
-func copyFile(src, dst string, preserve []string, info os.FileInfo, nums chan int64) error {
+func copyFile(src, dst string, preserve []string, info os.FileInfo, nums chan<- int64, errs chan<- error) {
 	r, err := os.Open(src)
 	if err != nil {
-		return err
+		errs <- err
+		return
 	}
 	defer r.Close()
 
@@ -67,30 +68,38 @@ func copyFile(src, dst string, preserve []string, info os.FileInfo, nums chan in
 	}
 	w, err := os.OpenFile(dst, os.O_RDWR|os.O_CREATE|os.O_TRUNC, dstMode)
 	if err != nil {
-		return err
+		errs <- err
+		return
 	}
 
 	if _, err := io.Copy(NewProgressWriter(w, nums), r); err != nil {
+		errs <- err
 		w.Close()
-		os.Remove(dst)
-		return err
+		if err = os.Remove(dst); err != nil {
+			errs <- err
+		}
+		return
 	}
 
 	if err := w.Close(); err != nil {
-		os.Remove(dst)
-		return err
+		errs <- err
+		if err = os.Remove(dst); err != nil {
+			errs <- err
+		}
+		return
 	}
 
 	if slices.Contains(preserve, "timestamps") {
 		atime := times.Get(info).AccessTime()
 		mtime := info.ModTime()
 		if err := os.Chtimes(dst, atime, mtime); err != nil {
-			os.Remove(dst)
-			return err
+			errs <- err
+			if err = os.Remove(dst); err != nil {
+				errs <- err
+			}
+			return
 		}
 	}
-
-	return nil
 }
 
 func copyAll(srcs []string, dstDir string, preserve []string) (nums chan int64, errs chan error) {
@@ -119,7 +128,7 @@ func copyAll(srcs []string, dstDir string, preserve []string) (nums chan int64,
 				dst = newPath
 			}
 
-			filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
+			err := filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
 				if err != nil {
 					errs <- fmt.Errorf("walk: %w", err)
 					return nil
@@ -153,12 +162,13 @@ func copyAll(srcs []string, dstDir string, preserve []string) (nums chan int64,
 					}
 					nums <- info.Size()
 				default:
-					if err := copyFile(path, newPath, preserve, info, nums); err != nil {
-						errs <- fmt.Errorf("copy: %w", err)
-					}
+					copyFile(path, newPath, preserve, info, nums, errs)
 				}
 				return nil
 			})
+			if err != nil {
+				errs <- fmt.Errorf("walk: %w", err)
+			}
 		}
 
 		for path, info := range dirInfos {

eval.go

@@ -747,8 +747,9 @@ func resetIncCmd(app *app) {
 	} else if gOpts.incfilter && app.ui.cmdPrefix == "filter: " {
 		dir := app.nav.currDir()
 		old := dir.ind
-		app.nav.setFilter(app.nav.prevFilter)
-		if old != dir.ind {
+		if err := app.nav.setFilter(app.nav.prevFilter); err != nil {
+			log.Printf("reset filter: %s", err)
+		} else if old != dir.ind {
 			app.ui.loadFile(app, true)
 		}
 	}

main.go

@@ -180,7 +180,9 @@ func checkServer() {
 		if _, err := os.Stat(gSocketPath); os.IsNotExist(err) {
 			startServer()
 		} else if _, err := net.Dial(gSocketProt, gSocketPath); err != nil {
-			os.Remove(gSocketPath)
+			if err := os.Remove(gSocketPath); err != nil {
+				log.Print(err)
+			}
 			startServer()
 		}
 	} else {
@@ -344,7 +346,9 @@ func main() {
 			log.Fatalf("remote command: %s", err)
 		}
 	case *serverMode:
-		os.Chdir(gUser.HomeDir)
+		if err := os.Chdir(gUser.HomeDir); err != nil {
+			log.Print(err)
+		}
 		serve()
 	default:
 		gSingleMode = *singleMode

misc.go

@@ -234,7 +234,7 @@ func readArrays(r io.Reader, minCols, maxCols int) ([][]string, error) {
 		arrays = append(arrays, arr)
 	}
 
-	return arrays, nil
+	return arrays, s.Err()
 }
 
 func readPairs(r io.Reader) ([][]string, error) {

nav.go

@@ -646,14 +646,18 @@ func (nav *nav) addJumpList() {
 func (nav *nav) cdJumpListPrev() {
 	if nav.jumpListInd > 0 {
 		nav.jumpListInd--
-		nav.cd(nav.jumpList[nav.jumpListInd])
+		if err := nav.cd(nav.jumpList[nav.jumpListInd]); err != nil {
+			log.Print(err)
+		}
 	}
 }
 
 func (nav *nav) cdJumpListNext() {
 	if nav.jumpListInd < len(nav.jumpList)-1 {
 		nav.jumpListInd++
-		nav.cd(nav.jumpList[nav.jumpListInd])
+		if err := nav.cd(nav.jumpList[nav.jumpListInd]); err != nil {
+			log.Print(err)
+		}
 	}
 }
 

server.go

@@ -111,12 +111,16 @@ Loop:
 				word2, rest2 := splitWord(rest)
 				id, err := strconv.Atoi(word2)
 				if err != nil {
-					for _, c := range gConnList {
-						fmt.Fprintln(c, rest)
+					for id, c2 := range gConnList {
+						if _, err := fmt.Fprintln(c2, rest); err != nil {
+							echoerrf(c, "failed to send command to client %v: %s", id, err)
+						}
 					}
 				} else {
 					if c2, ok := gConnList[id]; ok {
-						fmt.Fprintln(c2, rest2)
+						if _, err := fmt.Fprintln(c2, rest2); err != nil {
+							echoerrf(c, "failed to send command to client %v: %s", id, err)
+						}
 					} else {
 						echoerr(c, "listen: send: no such client id is connected")
 					}
@@ -138,10 +142,18 @@ Loop:
 				echoerr(c, "listen: query: no such client id is connected")
 				break
 			}
-			fmt.Fprintln(c2, "query "+rest2)
+			if _, err := fmt.Fprintln(c2, "query "+rest2); err != nil {
+				echoerrf(c, "failed to send query to client %v: %s", id, err)
+				break
+			}
 			s2 := bufio.NewScanner(c2)
 			for s2.Scan() && s2.Text() != "" {
-				fmt.Fprintln(c, s2.Text())
+				if _, err := fmt.Fprintln(c, s2.Text()); err != nil {
+					log.Printf("failed to forward query response from client %v: %s", id, err)
+				}
+			}
+			if s2.Err() != nil {
+				echoerrf(c, "failed to read query response from client %v: %s", id, s2.Err())
 			}
 		case "quit":
 			if len(gConnList) == 0 {

ui.go

@@ -1820,10 +1820,16 @@ func anyKey() {
 	if err != nil {
 		panic(err)
 	}
-	defer term.Restore(int(os.Stdin.Fd()), oldState)
+	defer func() {
+		if err := term.Restore(int(os.Stdin.Fd()), oldState); err != nil {
+			panic(err)
+		}
+	}()
 
 	b := make([]byte, 8)
-	os.Stdin.Read(b)
+	if _, err := os.Stdin.Read(b); err != nil {
+		log.Printf("Failed to read key press: %s", err)
+	}
 }
 
 func listMatches(screen tcell.Screen, matches []compMatch, selectedInd int) (string, *menuSelect) {

watch.go

@@ -71,7 +71,9 @@ func (watch *watch) add(path string) {
 
 	// ignore /dev since write updates to /dev/tty causes high cpu usage
 	if path != "/dev" {
-		watch.watcher.Add(path)
+		if err := watch.watcher.Add(path); err != nil {
+			log.Printf("watch path %s: %s", path, err)
+		}
 	}
 }