From e37aa358bf89337e1cab9885fcbcbef63c7ef153 Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Tue, 16 Feb 2021 06:50:12 +0000
Subject: [PATCH] Fix BUG_CASEEMPT: empty 'case' list was syntax error

'case x in esac' should be syntactically correct, but was an error:

	$ ksh -c 'case x in esac'
	ksh: syntax error at line 1: `case' unmatched

Inserting a newline was a workaround:

	$ ksh -c $'case x in\nesac'
	(no output)

The problem was that the 'esac' reserved word was not being
recognised if it immediately followed the 'in' reserved word.

src/cmd/ksh93/sh/lex.c: sh_lex():
- Do not turn off recognition of reserved words after 'in' if we're
  in a 'case' construct; only do this for 'for' and 'select'.

src/cmd/ksh93/tests/case.sh:
- Add seven regression test for correct recognition of 'esac'.
  Only two failed on ksh93. The rest is to catch future bugs.

Fixes: https://github.com/ksh93/ksh/issues/177
---
 NEWS                        |  3 +++
 src/cmd/ksh93/sh/lex.c      |  2 +-
 src/cmd/ksh93/tests/case.sh | 11 +++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index fecc39850..dcb02f114 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 2021-02-15:
 
+- Fixed a regression introduced by ksh93 (was not in ksh88): an empty 'case'
+  list on a single line ('case x in esac') was a syntax error.
+
 - Fixed a bug in the emacs built-in editor, introduced on 2020-09-17, that
   made the Meta-D and Meta-H keys delete single characters instead of words.
 
diff --git a/src/cmd/ksh93/sh/lex.c b/src/cmd/ksh93/sh/lex.c
index 31614b42c..64487b421 100644
--- a/src/cmd/ksh93/sh/lex.c
+++ b/src/cmd/ksh93/sh/lex.c
@@ -1503,7 +1503,7 @@ breakloop:
 			}
 			else
 				lp->lex.skipword = 0;
-			if(c==INSYM)
+			if(c==INSYM && !lp->lex.incase)
 				lp->lex.reservok = 0;
 			else if(c==TIMESYM)
 			{
diff --git a/src/cmd/ksh93/tests/case.sh b/src/cmd/ksh93/tests/case.sh
index 2ed08c1e3..9eb9a19db 100755
--- a/src/cmd/ksh93/tests/case.sh
+++ b/src/cmd/ksh93/tests/case.sh
@@ -84,4 +84,15 @@ esac') != b ]] && err_exit 'bug in ;& at end of script'
 x=$($SHELL -ec 'case a in a) echo 1; false; echo 2 ;& b) echo 3;; esac')
 [[ $x == 1 ]] || err_exit 'set -e ignored on case fail through'
 
+# ======
+# An empty 'case' list was a syntax error: https://github.com/ksh93/ksh/issues/177
+got=$(eval 'case x in esac' 2>&1) || err_exit "empty case list fails: got $(printf %q "$got")"
+got=$(eval ': || for i in esac; do :; done' 2>&1) || err_exit "'for i in esac' fails: got $(printf %q "$got")"
+got=$(eval ': || select i in esac; do :; done' 2>&1) || err_exit "'select i in esac' fails: got $(printf %q "$got")"
+(eval 'case x in esac) foo;; esac') 2>/dev/null && err_exit "unquoted 'esac' keyword as first selector fails to fail"
+(eval 'case x in y) bar;; esac) foo;; esac') 2>/dev/null && err_exit "unquoted 'esac' kwyword as nth selector fails to fail"
+got=$(eval 'case x in e\sac) foo;; esac' 2>&1) || err_exit "quoted 'esac' pattern (1) fails: got $(printf %q "$got")"
+got=$(eval 'case x in y) bar;; es\ac) foo;; esac' 2>&1) || err_exit "quoted 'esac' pattern (2) fails: got $(printf %q "$got")"
+
+# ======
 exit $((Errors<125?Errors:125))