Fix incompatibility of adaptive height and 'start:reload'

This command would cause a deadlock and make fzf crash:

  fzf --bind 'start:reload:ls' --height ~100%

Because,

1. 'start' event is handled by Terminal
2. When 'reload' is bound to 'start', fzf avoids starting the initial reader
3. Terminal waits for the initial input to find the right height when
   adaptive height is used
4. Because the initial reader is not started, Terminal never gets the
   initial list
5. No chance to trigger 'start:reload', hence deadlock

This commit fixes the above problem by extracting the reload command
bound to 'start' event and starting the initial reader with that command
instead of letting Terminal start it.

This commit also makes the environment variables available to
$FZF_DEFAULT_COMMAND.

  FZF_DEFAULT_COMMAND='echo $FZF_QUERY' fzf --query foo

Fix #3944

CHANGELOG.md

@@ -1,6 +1,14 @@
 CHANGELOG
 =========
 
+0.54.3
+------
+- Fixed incompatibility of adaptive height and 'start:reload'
+- Environment variables are now available to `$FZF_DEFAULT_COMMAND`
+  ```sh
+  FZF_DEFAULT_COMMAND='echo $FZF_QUERY' fzf --query foo
+  ```
+
 0.54.2
 ------
 - Fixed incorrect syntax highlighting of truncated multi-line entries

src/constants.go

@@ -58,7 +58,6 @@ const (
 const (
 	EvtReadNew util.EventType = iota
 	EvtReadFin
-	EvtReadNone
 	EvtSearchNew
 	EvtSearchProgress
 	EvtSearchFin

src/core.go

@@ -146,8 +146,23 @@ func Run(opts *Options) (int, error) {
 	// Process executor
 	executor := util.NewExecutor(opts.WithShell)
 
+	// Terminal I/O
+	var terminal *Terminal
+	var err error
+	var initialEnv []string
+	initialReload := opts.extractReloadOnStart()
+	if opts.Filter == nil {
+		terminal, err = NewTerminal(opts, eventBox, executor)
+		if err != nil {
+			return ExitError, err
+		}
+		initialEnv = terminal.environ()
+		var temps []string
+		initialReload, temps = terminal.replacePlaceholderInInitialCommand(initialReload)
+		defer removeFiles(temps)
+	}
+
 	// Reader
-	reloadOnStart := opts.reloadOnStart()
 	streamingFilter := opts.Filter != nil && !sort && !opts.Tac && !opts.Sync
 	var reader *Reader
 	if !streamingFilter {
@@ -155,12 +170,7 @@ func Run(opts *Options) (int, error) {
 			return chunkList.Push(data)
 		}, eventBox, executor, opts.ReadZero, opts.Filter == nil)
 
-		if reloadOnStart {
-			// reload or reload-sync action is bound to 'start' event, no need to start the reader
-			eventBox.Set(EvtReadNone, nil)
-		} else {
-			go reader.ReadSource(opts.Input, opts.WalkerRoot, opts.WalkerOpts, opts.WalkerSkip)
-		}
+		go reader.ReadSource(opts.Input, opts.WalkerRoot, opts.WalkerOpts, opts.WalkerSkip, initialReload, initialEnv)
 	}
 
 	// Matcher
@@ -212,7 +222,7 @@ func Run(opts *Options) (int, error) {
 					}
 					return false
 				}, eventBox, executor, opts.ReadZero, false)
-			reader.ReadSource(opts.Input, opts.WalkerRoot, opts.WalkerOpts, opts.WalkerSkip)
+			reader.ReadSource(opts.Input, opts.WalkerRoot, opts.WalkerOpts, opts.WalkerSkip, initialReload, initialEnv)
 		} else {
 			eventBox.Unwatch(EvtReadNew)
 			eventBox.WaitFor(EvtReadFin)
@@ -234,8 +244,7 @@ func Run(opts *Options) (int, error) {
 	}
 
 	// Synchronous search
-	sync := opts.Sync && !reloadOnStart
-	if sync {
+	if opts.Sync {
 		eventBox.Unwatch(EvtReadNew)
 		eventBox.WaitFor(EvtReadFin)
 	}
@@ -244,18 +253,14 @@ func Run(opts *Options) (int, error) {
 	go matcher.Loop()
 	defer matcher.Stop()
 
-	// Terminal I/O
-	terminal, err := NewTerminal(opts, eventBox, executor)
-	if err != nil {
-		return ExitError, err
-	}
+	// Handling adaptive height
 	maxFit := 0 // Maximum number of items that can fit on screen
 	padHeight := 0
 	heightUnknown := opts.Height.auto
 	if heightUnknown {
 		maxFit, padHeight = terminal.MaxFitAndPad()
 	}
-	deferred := opts.Select1 || opts.Exit0 || sync
+	deferred := opts.Select1 || opts.Exit0 || opts.Sync
 	go terminal.Loop()
 	if !deferred && !heightUnknown {
 		// Start right away
@@ -322,9 +327,6 @@ func Run(opts *Options) (int, error) {
 					err = quitSignal.err
 					stop = true
 					return
-				case EvtReadNone:
-					reading = false
-					terminal.UpdateCount(0, false, nil)
 				case EvtReadNew, EvtReadFin:
 					if evt == EvtReadFin && nextCommand != nil {
 						restart(*nextCommand, nextEnviron)

src/options.go

@@ -2964,17 +2964,18 @@ func ParseOptions(useDefaults bool, args []string) (*Options, error) {
 	return opts, nil
 }
 
-func (opts *Options) reloadOnStart() bool {
-	// Not compatible with --filter
-	if opts.Filter != nil {
-		return false
-	}
+func (opts *Options) extractReloadOnStart() string {
+	cmd := ""
 	if actions, prs := opts.Keymap[tui.Start.AsEvent()]; prs {
+		filtered := []*action{}
 		for _, action := range actions {
 			if action.t == actReload || action.t == actReloadSync {
-				return true
+				cmd = action.a
+			} else {
+				filtered = append(filtered, action)
 			}
 		}
+		opts.Keymap[tui.Start.AsEvent()] = filtered
 	}
-	return false
+	return cmd
 }

src/reader.go

@@ -111,18 +111,20 @@ func (r *Reader) readChannel(inputChan chan string) bool {
 }
 
 // ReadSource reads data from the default command or from standard input
-func (r *Reader) ReadSource(inputChan chan string, root string, opts walkerOpts, ignores []string) {
+func (r *Reader) ReadSource(inputChan chan string, root string, opts walkerOpts, ignores []string, initCmd string, initEnv []string) {
 	r.startEventPoller()
 	var success bool
 	if inputChan != nil {
 		success = r.readChannel(inputChan)
+	} else if len(initCmd) > 0 {
+		success = r.readFromCommand(initCmd, initEnv)
 	} else if util.IsTty(os.Stdin) {
 		cmd := os.Getenv("FZF_DEFAULT_COMMAND")
 		if len(cmd) == 0 {
 			success = r.readFiles(root, opts, ignores)
 		} else {
 			// We can't export FZF_* environment variables to the default command
-			success = r.readFromCommand(cmd, nil)
+			success = r.readFromCommand(cmd, initEnv)
 		}
 	} else {
 		success = r.readFromStdin()

src/terminal.go

@@ -2946,6 +2946,10 @@ type replacePlaceholderParams struct {
 	executor   *util.Executor
 }
 
+func (t *Terminal) replacePlaceholderInInitialCommand(template string) (string, []string) {
+	return t.replacePlaceholder(template, false, string(t.input), []*Item{nil, nil})
+}
+
 func (t *Terminal) replacePlaceholder(template string, forcePlus bool, input string, list []*Item) (string, []string) {
 	return replacePlaceholder(replacePlaceholderParams{
 		template:   template,