From 6a5bf9b1438ed0b721657568fbb3a7c0b829e89e Mon Sep 17 00:00:00 2001
From: Guillaume Maudoux <layus.on@gmail.com>
Date: Tue, 14 Jun 2016 17:42:46 +0200
Subject: [PATCH] simplify handling of extra '}'

---
 src/libexpr/lexer.l | 33 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 18 deletions(-)

diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index a052447d..c34e5c38 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -6,9 +6,9 @@
 %option nounput noyy_top_state
 
 
+%s DEFAULT
 %x STRING
 %x IND_STRING
-%x INSIDE_DOLLAR_CURLY
 
 
 %{
@@ -99,8 +99,6 @@ URI         [a-zA-Z][a-zA-Z0-9\+\-\.]*\:[a-zA-Z0-9\%\/\?\:\@\&\=\+\$\,\-\_\.\!\~
 
 %%
 
-<INITIAL,INSIDE_DOLLAR_CURLY>{
-
 
 if          { return IF; }
 then        { return THEN; }
@@ -140,17 +138,19 @@ or          { return OR_KW; }
               return FLOAT;
             }
 
-\$\{        { PUSH_STATE(INSIDE_DOLLAR_CURLY); return DOLLAR_CURLY; }
-}
+\$\{        { PUSH_STATE(DEFAULT); return DOLLAR_CURLY; }
 
-\}                           { return '}'; }
-<INSIDE_DOLLAR_CURLY>\}      { POP_STATE(); return '}'; }
-\{                           { return '{'; }
-<INSIDE_DOLLAR_CURLY>\{      { PUSH_STATE(INSIDE_DOLLAR_CURLY); return '{'; }
+\}          { /* State INITIAL only exists at the bottom of the stack and is
+                 used as a marker. DEFAULT replaces it everywhere else.
+                 Popping when in INITIAL state causes an empty stack exception,
+                 so don't */
+              if (YYSTATE != INITIAL)
+                POP_STATE();
+              return '}';
+            }
+\{          { PUSH_STATE(DEFAULT); return '{'; }
 
-<INITIAL,INSIDE_DOLLAR_CURLY>\" {
-                PUSH_STATE(STRING); return '"';
-              }
+\"          { PUSH_STATE(STRING); return '"'; }
 <STRING>([^\$\"\\]|\$[^\{\"\\]|\\{ANY}|\$\\{ANY})*\$/\" |
 <STRING>([^\$\"\\]|\$[^\{\"\\]|\\{ANY}|\$\\{ANY})+ {
                 /* It is impossible to match strings ending with '$' with one
@@ -159,7 +159,7 @@ or          { return OR_KW; }
                 yylval->e = unescapeStr(data->symbols, yytext, yyleng);
                 return STR;
               }
-<STRING>\$\{  { PUSH_STATE(INSIDE_DOLLAR_CURLY); return DOLLAR_CURLY; }
+<STRING>\$\{  { PUSH_STATE(DEFAULT); return DOLLAR_CURLY; }
 <STRING>\"    { POP_STATE(); return '"'; }
 <STRING>\$|\\|\$\\ {
                 /* This can only occur when we reach EOF, otherwise the above
@@ -169,7 +169,7 @@ or          { return OR_KW; }
                 return STR;
               }
 
-<INITIAL,INSIDE_DOLLAR_CURLY>\'\'(\ *\n)?     { PUSH_STATE(IND_STRING); return IND_STRING_OPEN; }
+\'\'(\ *\n)?     { PUSH_STATE(IND_STRING); return IND_STRING_OPEN; }
 <IND_STRING>([^\$\']|\$[^\{\']|\'[^\'\$])+ {
                    yylval->e = new ExprIndStr(yytext);
                    return IND_STR;
@@ -187,14 +187,13 @@ or          { return OR_KW; }
                    yylval->e = unescapeStr(data->symbols, yytext + 2, yyleng - 2);
                    return IND_STR;
                  }
-<IND_STRING>\$\{ { PUSH_STATE(INSIDE_DOLLAR_CURLY); return DOLLAR_CURLY; }
+<IND_STRING>\$\{ { PUSH_STATE(DEFAULT); return DOLLAR_CURLY; }
 <IND_STRING>\'\' { POP_STATE(); return IND_STRING_CLOSE; }
 <IND_STRING>\'   {
                    yylval->e = new ExprIndStr("'");
                    return IND_STR;
                  }
 
-<INITIAL,INSIDE_DOLLAR_CURLY>{
 
 {PATH}      { if (yytext[yyleng-1] == '/')
                   throw ParseError("path '%s' has a trailing slash", yytext);
@@ -219,7 +218,5 @@ or          { return OR_KW; }
               return (unsigned char) yytext[0];
             }
 
-}
-
 %%