Fix single quotes in expansion operator string (re: 5ed9ffd6)

The referenced commit introduced the following bug:

> The closing quote does not appear to be registering during the
> parse of the following:
>
>	echo ${var:+'{}'}
>
> Within a script, this will result in:
>
>	syntax error at line 1: `'' unmatched

src/cmd/ksh93/data/lexstates.c,
src/cmd/ksh93/include/lexstates.h:
- Add new ST_MOD1 state table that is a copy of ST_QUOTE, but adds
  a special meaning (ST_LIT) for the single quote (position 39).

src/cmd/ksh93/sh/lex.c: sh_lex():
- For parameter expansion operators with old-style quoting
  (S_MOD1), use the new ST_MOD1 state table instead of ST_QUOTE.
  This causes single quotes within them to be processed properly.

src/cmd/ksh93/tests/quoting2.sh:
- Add tests.

Thanks to @gkamat for the bug report.
Resolves: https://github.com/ksh93/ksh/issues/290

NEWS

@@ -3,6 +3,11 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2021-04-30:
+
+- Fixed a bug introduced on 2020-09-05 that caused "echo ${var:+'{}'}"
+  to be misparsed.
+
 2021-04-26:
 
 - Fixed a bug introduced on 2021-02-20 in which a shared-state command

src/cmd/ksh93/data/lexstates.c

@@ -387,6 +387,30 @@ static const char sh_lexstate9[256] =
 	0,	0,	0,	S_BRACE,S_PAT,	S_ENDCH,0,	0
 };
 
+/*
+ * ST_MOD1
+ * for skipping over a string S in ${v-S}, ${v+S}, ${v:-S}, ${v:+S}
+ */
+static const char sh_lexstate11[256] =
+{
+	S_EOF,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	S_NL,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	S_QUOTE,0,	S_DOL,	0,	0,	S_LIT,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	S_ESC,	0,	0,	0,
+	S_GRAVE,0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	S_RBRA,	0,	0
+};
+
 /*
  * This must be kept synchronous with all the above and the ST_* definitions in lexstates.h
  */
@@ -394,7 +418,7 @@ const char *sh_lexrstates[ST_NONE] =
 {
 	sh_lexstate0, sh_lexstate1, sh_lexstate2, sh_lexstate3,
 	sh_lexstate4, sh_lexstate5, sh_lexstate6, sh_lexstate7,
-	sh_lexstate8, sh_lexstate9, sh_lexstate5
+	sh_lexstate8, sh_lexstate9, sh_lexstate5, sh_lexstate11
 };
 
 

src/cmd/ksh93/include/lexstates.h

@@ -79,7 +79,8 @@
 #define ST_DOLNAME	8
 #define ST_MACRO	9
 #define ST_QNEST	10
-#define ST_NONE		11
+#define ST_MOD1		11
+#define ST_NONE		12
 
 #include "FEATURE/locale"
 

src/cmd/ksh93/include/version.h

@@ -21,7 +21,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2021-04-26"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2021-04-30"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2021 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/sh/lex.c

@@ -992,7 +992,7 @@ int sh_lex(Lex_t* lp)
 				mode = ST_NESTED;
 				continue;
 			case S_MOD1:
-				mode = ST_QUOTE;
+				mode = ST_MOD1;
 				continue;
 			case S_MOD2:
 #if SHOPT_KIA

src/cmd/ksh93/tests/quoting2.sh

@@ -250,5 +250,18 @@ actual=$(printf %q $'1\x[11]1')
 [[ $actual == "$expect" ]] || err_exit 'shell-quoting: hex bytes not protected from subsequent hex-like chars' \
 				"(expected $expect; got $actual)"
 
+# ======
+# https://github.com/ksh93/ksh/issues/290
+var=dummy
+exp='{}'
+got=$(eval 'echo ${var:+'\''{}'\''}' 2>&1)
+[[ $got == "$exp" ]] || err_exit "Single quotes misparsed in expansion operator string (1)" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+unset var
+exp='}'
+got=$(eval 'echo ${var:-'\''}'\''}' 2>&1)
+[[ $got == "$exp" ]] || err_exit "Single quotes misparsed in expansion operator string (2)" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+
 # ======
 exit $((Errors<125?Errors:125))