Add 'transform' action to conditionally perform a series of actions

'transform' action runs an external command that prints a series of
actions to perform.

  # Disallow selecting an empty line
  echo -e "1. Hello\n2. Goodbye\n\n3. Exit" |
    fzf --reverse --header 'Select one' \
        --bind 'enter:transform:[[ -n {} ]] && echo accept || echo "change-header:Invalid selection"'

  # Move cursor past the empty line
  echo -e "1. Hello\n2. Goodbye\n\n3. Exit" |
    fzf --reverse --header 'Select one' \
        --bind 'enter:transform:[[ -n {} ]] && echo accept || echo "change-header:Invalid selection"' \
        --bind 'focus:transform:[[ -n {} ]] && exit; [[ {fzf:action} =~ up$ ]] && echo up || echo down'

Close #3368
Close #2980

CHANGELOG.md

@@ -3,6 +3,22 @@ CHANGELOG
 
 0.45.0
 ------
+- Added `transform` action to conditionally perform a series of actions
+  ```sh
+  # Disallow selecting an empty line
+  echo -e "1. Hello\n2. Goodbye\n\n3. Exit" |
+    fzf --reverse --header 'Select one' \
+        --bind 'enter:transform:[[ -n {} ]] && echo accept || echo "change-header:Invalid selection"'
+
+  # Move cursor past the empty line
+  echo -e "1. Hello\n2. Goodbye\n\n3. Exit" |
+    fzf --reverse --header 'Select one' \
+        --bind 'enter:transform:[[ -n {} ]] && echo accept || echo "change-header:Invalid selection"' \
+        --bind 'focus:transform:[[ -n {} ]] && exit; [[ {fzf:action} =~ up$ ]] && echo up || echo down'
+  ```
+- Added placeholder expressions
+    - `{fzf:action}` - the name of the last action performed
+    - `{fzf:query}` - synonym for `{q}`
 - Added support for negative height
   ```sh
   # Terminal height minus 1, so you can still see the command line

Makefile

@@ -89,6 +89,9 @@ bench:
 
 install: bin/fzf
 
+generate:
+	PATH=$(PATH):$(GOPATH)/bin $(GO) generate ./...
+
 build:
 	goreleaser build --rm-dist --snapshot --skip-post-hooks
 
@@ -181,4 +184,4 @@ update:
 	$(GO) get -u
 	$(GO) mod tidy
 
-.PHONY: all build release test bench install clean docker docker-test update
+.PHONY: all generate build release test bench install clean docker docker-test update

go.mod

@@ -14,8 +14,10 @@ require (
 require (
 	github.com/gdamore/encoding v1.0.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
-	golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4 // indirect
+	golang.org/x/mod v0.14.0 // indirect
+	golang.org/x/sync v0.5.0 // indirect
 	golang.org/x/text v0.5.0 // indirect
+	golang.org/x/tools v0.16.1 // indirect
 )
 
 go 1.17

go.sum

@@ -19,13 +19,17 @@ github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5t
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/mod v0.14.0 h1:dGoOF9QVLYng8IHTm7BAyWqCqSheQ5pYWGhzW00YJr0=
+golang.org/x/mod v0.14.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4 h1:uVc8UZUe6tr40fFVnUP5Oj+veunVezqYl9z7DYw9xzw=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.5.0 h1:60k92dhOjHxJkrqnwsfl8KuaHbn/5dl0lUPUklKo3qE=
+golang.org/x/sync v0.5.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
@@ -46,4 +50,6 @@ golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+golang.org/x/tools v0.16.1 h1:TLyB3WofjdOEepBHAU20JdNC1Zbg87elYofWYAY5oZA=
+golang.org/x/tools v0.16.1/go.mod h1:kYVVN6I1mBNoB1OX+noeBjbRk4IUEPa7JJ+TJMEooJ0=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

man/man1/fzf.1

@@ -574,10 +574,6 @@ e.g.
 When using a field index expression, leading and trailing whitespace is stripped
 from the replacement string. To preserve the whitespace, use the \fBs\fR flag.
 
-Also, \fB{q}\fR is replaced to the current query string, and \fB{n}\fR is
-replaced to zero-based ordinal index of the line. Use \fB{+n}\fR if you want
-all index numbers when multiple lines are selected.
-
 A placeholder expression with \fBf\fR flag is replaced to the path of
 a temporary file that holds the evaluated list. This is useful when you
 multi-select a large number of items and the length of the evaluated string may
@@ -589,6 +585,15 @@ e.g.
      seq 100000 | fzf --multi --bind ctrl-a:select-all \\
                       --preview "awk '{sum+=\\$1} END {print sum}' {+f}"\fR
 
+Also,
+
+* \fB{q}\fR (or \fB{fzf:query}\fR) is replaced to the current query string
+.br
+* \fB{n}\fR is replaced to the zero-based ordinal index of the current item.
+  Use \fB{+n}\fR if you want all index numbers when multiple lines are selected.
+.br
+* \fB{fzf:action}\fR is replaced to to the name of the last action performed
+
 Note that you can escape a placeholder pattern by prepending a backslash.
 
 Preview window will be updated even when there is no match for the current

src/options.go

@@ -979,7 +979,7 @@ const (
 
 func init() {
 	executeRegexp = regexp.MustCompile(
-		`(?si)[:+](become|execute(?:-multi|-silent)?|reload(?:-sync)?|preview|(?:change|transform)-(?:header|query|prompt|border-label|preview-label)|change-preview-window|change-preview|(?:re|un)bind|pos|put)`)
+		`(?si)[:+](become|execute(?:-multi|-silent)?|reload(?:-sync)?|preview|(?:change|transform)-(?:header|query|prompt|border-label|preview-label)|transform|change-preview-window|change-preview|(?:re|un)bind|pos|put)`)
 	splitRegexp = regexp.MustCompile("[,:]+")
 	actionNameRegexp = regexp.MustCompile("(?i)^[a-z-]+")
 }
@@ -1086,15 +1086,15 @@ func parseActionList(masked string, original string, prevActions []*action, putA
 		case "backward-delete-char":
 			appendAction(actBackwardDeleteChar)
 		case "backward-delete-char/eof":
-			appendAction(actBackwardDeleteCharEOF)
+			appendAction(actBackwardDeleteCharEof)
 		case "backward-word":
 			appendAction(actBackwardWord)
 		case "clear-screen":
 			appendAction(actClearScreen)
 		case "delete-char":
 			appendAction(actDeleteChar)
 		case "delete-char/eof":
-			appendAction(actDeleteCharEOF)
+			appendAction(actDeleteCharEof)
 		case "deselect":
 			appendAction(actDeselect)
 		case "end-of-line":
@@ -1213,7 +1213,7 @@ func parseActionList(masked string, original string, prevActions []*action, putA
 			appendAction(actDisableSearch)
 		case "put":
 			if putAllowed {
-				appendAction(actRune)
+				appendAction(actChar)
 			} else {
 				exit("unable to put non-printable character")
 			}
@@ -1333,6 +1333,8 @@ func isExecuteAction(str string) actionType {
 		return actExecuteMulti
 	case "put":
 		return actPut
+	case "transform":
+		return actTransform
 	case "transform-border-label":
 		return actTransformBorderLabel
 	case "transform-preview-label":