lint: check for bad white space habits

A little coding hygiene cannot hurt. Add a simple awk script to check
all source files for bad white space habits:

- trailing white space
- trailing new lines at the end of files
- missing new line at the end of files
- spaces followed by tabs

The script outputs color when the terminal supports it. It exits with
a non-zero code when there was at least one white space issue found.
Call the script in the lint step.

Example output of the awk script:

 config/default_styleset:1:# <-- trailing whitespace
 config/default_styleset:3:# <-- trailing whitespace
 doc/aerc.1.scd:78:        Executes an arbitrary command in the background. Aerc will set the <-- trailing whitespace
 doc/aerc.1.scd:234:        <-- trailing whitespace
 doc/aerc.1.scd:237:        <-- trailing whitespace
 worker/types/thread_test.go:74:        //         return ErrSkipThread<-- space(s) followed by tab(s)
 worker/lib/testdata/message/invalid/hexa: trailing new line(s)

Fix issues reported by the script.

NB: The ENDFILE match is a GNU extension. It will be ignored on BSD-awk
and trailing new lines will not be detected. The lint make target is
only invoked on alpine linux which has GNU awk anyway.

NB: Empty cells in scdoc tables require trailing white space... Avoid
this by setting content in these cells. I don't really see a use for
empty cells.

Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Moritz Poldrack <moritz@poldrack.dev>

9 files changed, 77 insertions, 39 deletions

diff --git a/Makefile b/Makefile
index 04ee08e4..7f1837a9 100644
--- a/Makefile
+++ b/Makefile
@@ -61,6 +61,7 @@ fmt:
 
 .PHONY: lint
 lint:
+	@contrib/check-whitespace `git ls-files` && echo white space ok.
 	@$(GO) run mvdan.cc/gofumpt -l . | grep ^ \
 		&& echo The above files need to be formatted, please run make fmt && exit 1 \
 		|| echo all files formatted.
diff --git a/config/default_styleset b/config/default_styleset
index ae3b9e81..30baf970 100644
--- a/config/default_styleset
+++ b/config/default_styleset
@@ -1,6 +1,6 @@
-# 
+#
 # aerc default styleset
-# 
+#
 # This styleset uses the terminal defaults as its base.
 # More information on how to configure the styleset can be found in
 # the aerc-stylesets(7) manpage. Please read the manual before
diff --git a/contrib/check-whitespace b/contrib/check-whitespace
new file mode 100755
index 00000000..5afd2f4c
--- /dev/null
+++ b/contrib/check-whitespace
@@ -0,0 +1,51 @@
+#!/usr/bin/awk -f
+
+BEGIN {
+	isatty = system("test -t 1") == "0"
+	retcode = 0
+}
+
+function color(code, s) {
+	if (isatty) {
+		return "\033[" code "m" s "\033[0m"
+	}
+	return s
+}
+function red(s) { return color("31", s) }
+function green(s) { return color("32", s) }
+function magenta(s) { return color("35", s) }
+function cyan(s) { return color("36", s) }
+function bg_red(s) { return color("41", s) }
+function hl_ws(s, pattern) {
+	gsub(pattern, bg_red("&"), s)
+	# convert tab characters to 8 spaces to allow coloring
+	gsub(/\t/, "        ", s)
+	return s
+}
+
+/ +\t+/ {
+	retcode = 1
+	print magenta(FILENAME) cyan(":") green(FNR) cyan(":") \
+		hl_ws($0, " +\\t+") red("<-- space(s) followed by tab(s)")
+}
+
+/[ \t]+$/ {
+	retcode = 1
+	print magenta(FILENAME) cyan(":") green(FNR) cyan(":") \
+		hl_ws($0, "[ \\t]+$") red("<-- trailing whitespace")
+}
+
+ENDFILE {
+	# will only match on GNU awk, ignored on non-GNU versions
+	if ($0 ~ /^[ \t]*$/) {
+		retcode = 1
+		print magenta(FILENAME) cyan(": ") red("trailing new line(s)")
+	} else if (RT != "\n") {
+		retcode = 1
+		print magenta(FILENAME) cyan(": ") red("no new line at end of file")
+	}
+}
+
+END {
+	exit retcode
+}
diff --git a/doc/aerc-config.5.scd b/doc/aerc-config.5.scd
index 21472e6e..a09c5ab8 100644
--- a/doc/aerc-config.5.scd
+++ b/doc/aerc-config.5.scd
@@ -390,7 +390,7 @@ These options are configured in the *[statusline]* section of aerc.conf.
 |  %T
 :  general on/off information (e.g. passthrough, threading, sorting)
 |  %>
-:  does not print anything but all format specifier that follow will be right justified. 
+:  does not print anything but all format specifier that follow will be right justified.
 
 *separator*
 	Specifies the separator between grouped statusline elements (e.g. for
@@ -854,7 +854,7 @@ each binding context:
 *$ex*
 	This can be set to a keystroke which will bring up the command input in this
 	context.
-	
+
 	Default: ':'
 
 In addition to letters, special keys may be specified in <angle brackets>. The
@@ -867,63 +867,63 @@ following special keys are supported:
 |  semicolon
 :  ;
 |  tab
-:  
+:  Tab
 |  enter
-:  
+:  Enter
 |  up
-:  
+:  Up arrow
 |  c-up
 :  Ctrl+Up
 |  a-up
 :  Alt+Up
 |  down
-:  
+:  Down arrow
 |  c-down
 :  Ctrl+Down
 |  a-down
 :  Alt+Down
 |  right
-:  
+:  Right arrow
 |  c-right
 :  Ctrl+Right
 |  a-right
 :  Alt+Right
 |  left
-:  
+:  Left arrow
 |  c-left
 :  Ctrl+Left
 |  a-left
 :  Alt+Left
 |  pgup
-:  
+:  Page Up
 |  c-pgup
 :  Ctrl+PageUp
 |  a-pgup
 :  Alt+PageUp
 |  pgdn
-:  
+:  Page Down
 |  c-pgdn
 :  Ctrl+PageDn
 |  a-pgdn
 :  Alt+PageDn
 |  home
-:  
+:  Home
 |  end
-:  
+:  End
 |  insert
-:  
+:  Insert
 |  delete
-:  
+:  Delete
 |  exit
-:  
+:  Exit
 |  cancel
-:  
+:  Cancel
 |  print
-:  
+:  Print screen
 |  pause
-:  
+:  Pause
 |  backtab
-: 
+:  Shift+Tab
 |  c-space
 :  Ctrl+Space
 |  a-space
diff --git a/doc/aerc-stylesets.7.scd b/doc/aerc-stylesets.7.scd
index 3b5dc232..0cb5a322 100644
--- a/doc/aerc-stylesets.7.scd
+++ b/doc/aerc-stylesets.7.scd
@@ -83,11 +83,10 @@ styling.
 [[ *Style Object*
 :[ *Description*
 |  default
-:  The default style object used for normal ui elements while not
-   using specialized configuration.
+:  The default style object used for normal ui elements while not using specialized configuration.
 |  error
 :  The style used to show errors.
-|  warning 
+|  warning
 :  The style used when showing warnings.
 |  success
 :  The style used for success messages.
@@ -158,8 +157,7 @@ For example, the following wildcards can be made using this syntax.
 |  \*.fg=blue
 :  Set the foreground color of all style objects to blue.
 |  \*list.bg=hotpink
-:  Set the background color of all style objects that end in list 
-   to hotpink.
+:  Set the background color of all style objects that end in list to hotpink.
 
 ## Selected modifier
 Selected modifier can be applied to any style object. The style provided for
diff --git a/doc/aerc.1.scd b/doc/aerc.1.scd
index dbf782ce..ea4be171 100644
--- a/doc/aerc.1.scd
+++ b/doc/aerc.1.scd
@@ -76,7 +76,7 @@ These commands work in any context.
 	as a delta from the selected tab.
 
 *exec* <command...>
-	Executes an arbitrary command in the background. Aerc will set the 
+	Executes an arbitrary command in the background. Aerc will set the
 	environment variables *$account* and *$folder* when the command is
 	executed from an Account tab or an opened message.
 
@@ -237,10 +237,8 @@ message list, the message in the message viewer, etc).
 
 	Seen
 		Message has been read
-	
 	Answered
 		Message has been answered
-	
 	Flagged
 		Message is flagged for urgent/special attention
 
diff --git a/worker/lib/testdata/message/invalid/hexa b/worker/lib/testdata/message/invalid/hexa
index 2967a198..56b352ff 100644
--- a/worker/lib/testdata/message/invalid/hexa
+++ b/worker/lib/testdata/message/invalid/hexa
@@ -24,5 +24,3 @@ Content-Type: text/html; charset=utf-8
 <ObJECT>
 
 --Nextpart_1Q2YJhd197991794467076Pgfa--
-
-
diff --git a/worker/notmuch/worker.go b/worker/notmuch/worker.go
index f1533e12..38539df5 100644
--- a/worker/notmuch/worker.go
+++ b/worker/notmuch/worker.go
@@ -135,18 +135,13 @@ func (w *worker) handleMessage(msg types.WorkerMessage) error {
 	case *types.CheckMail:
 		go w.handleCheckMail(msg)
 		return nil
-
 		// not implemented, they are generally not used
 		// in a notmuch based workflow
 		// case *types.DeleteMessages:
 		// case *types.CopyMessages:
-		// 	return w.handleCopyMessages(msg)
 		// case *types.AppendMessage:
-		// 	return w.handleAppendMessage(msg)
 		// case *types.CreateDirectory:
-		// 	return w.handleCreateDirectory(msg)
 		// case *types.RemoveDirectory:
-		//  return w.handleRemoveDirectory(msg)
 	}
 	return errUnsupported
 }
diff --git a/worker/types/thread_test.go b/worker/types/thread_test.go
index 803f7ba9..b3c39322 100644
--- a/worker/types/thread_test.go
+++ b/worker/types/thread_test.go
@@ -70,9 +70,6 @@ func TestNewWalk(t *testing.T) {
 	var prefix []string
 	lastLevel := 0
 	tree.Walk(func(t *Thread, lvl int, e error) error {
-		// if t.Uid%2 != 0 {
-		// 	return ErrSkipThread
-		// }
 		if e != nil {
 			fmt.Printf("ERROR: %v\n", e)
 		}