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ref: b562b269cea44e09d3c642b1a9452e16bd8ce3b5
parent: 4ec97f73ee2326209bc56730562e82f2e6fe2c0a
author: Alex Musolino <alex@musolino.id.au>
date: Sat Feb 6 00:21:09 EST 2021

test: fix expression parser

The old parser code was rubbish and only worked for trivial
expressions.  The new code properly handles complex expressions,
including short circuit evaluation.

As such, the BUGS section has been removed from the test(1) man page.
The description of an unimplemented feature has also been removed.

--- a/sys/man/1/test
+++ b/sys/man/1/test
@@ -100,11 +100,6 @@
 .BR -le
 may be used in place of
 .BR -eq .
-The (nonstandard) construct
-.BI -l " string\f1,
-meaning the length of
-.IR string ,
-may be used in place of an integer.
 .TP
 .IB a " -nt " b
 True if file
@@ -209,10 +204,3 @@
 .B /sys/src/cmd/test.c
 .SH "SEE ALSO"
 .IR rc (1) 
-.SH BUGS
-Won't complain about extraneous arguments
-since there may be arguments left unprocessed by
-short-circuit evaluation of
-.B -a
-or
-.BR -o .
--- a/sys/src/cmd/test.c
+++ b/sys/src/cmd/test.c
@@ -30,7 +30,7 @@
 int	isnewerthan(char *, char *);
 int	hasmode(char *, ulong);
 int	tio(char *, int);
-int	e(void), e1(void), e2(void), e3(void);
+int	e(int), e1(int), e2(int), e3(int);
 char	*nxtarg(int);
 
 void
@@ -47,12 +47,8 @@
 	argv[ac] = 0;
 	if (ac<=1)
 		exits("usage");
-	r = e();
-	/*
-	 * nice idea but short-circuit -o and -a operators may have
-	 * not consumed their right-hand sides.
-	 */
-	if(0 && (c = nxtarg(1)) != nil)
+	r = e(1);
+	if((c = nxtarg(1)) != nil)
 		synbad("unexpected operator/operand: ", c);
 	exits(r?0:"false");
 }
@@ -81,78 +77,128 @@
 }
 
 int
-e(void)
+e(int eval)
 {
+	char *op;
 	int p1;
 
-	p1 = e1();
-	if (EQ(nxtarg(1), "-o"))
-		return(p1 || e());
-	ap--;
-	return(p1);
+	p1 = e1(eval);
+	for(;;){
+		op = nxtarg(1);
+		if(op == nil)
+			break;
+		if(!EQ(op, "-o")){
+			ap--;
+			return p1;
+		}
+		if(!p1 && eval)
+			p1 |= e1(1);
+		else
+			e1(0);
+	}
+	return p1;
 }
 
 int
-e1(void)
+e1(int eval)
 {
+	char *op;
 	int p1;
 
-	p1 = e2();
-	if (EQ(nxtarg(1), "-a"))
-		return (p1 && e1());
-	ap--;
-	return(p1);
+	p1 = e2(eval);
+	for(;;){
+		op = nxtarg(1);
+		if(op == nil)
+			break;
+		if(!EQ(op, "-a")){
+			ap--;
+			return p1;
+		}
+		if(p1 && eval)
+			p1 &= e2(1);
+		else
+			e2(0);
+	}
+	return p1;
 }
 
 int
-e2(void)
+e2(int eval)
 {
-	if (EQ(nxtarg(0), "!"))
-		return(!e2());
+	char *op;
+	int p1;
+
+	p1 = 0;
+	for(;;){
+		op = nxtarg(1);
+		if(op == nil)
+			return p1 ^ 1;
+		if(!EQ(op, "!"))
+			break;
+		p1 ^= 1;
+	}
 	ap--;
-	return(e3());
+	return(p1^e3(eval));
 }
 
 int
-e3(void)
+e3(int eval)
 {
 	int p1, int1, int2;
-	char *a, *p2;
+	char *a, *b, *p2;
 
 	a = nxtarg(0);
 	if(EQ(a, "(")) {
-		p1 = e();
+		p1 = e(eval);
 		if(!EQ(nxtarg(0), ")"))
 			synbad(") expected","");
 		return(p1);
 	}
 
-	if(EQ(a, "-A"))
-		return(hasmode(nxtarg(0), DMAPPEND));
+	if(EQ(a, "-A")){
+		b = nxtarg(0);
+		return(eval && hasmode(b, DMAPPEND));
+	}
 
-	if(EQ(a, "-L"))
-		return(hasmode(nxtarg(0), DMEXCL));
+	if(EQ(a, "-L")){
+		b = nxtarg(0);
+		return(eval && hasmode(b, DMEXCL));
+	}
 
-	if(EQ(a, "-T"))
-		return(hasmode(nxtarg(0), DMTMP));
+	if(EQ(a, "-T")){
+		b = nxtarg(0);
+		return(eval && hasmode(b, DMTMP));
+	}
 
-	if(EQ(a, "-f"))
-		return(isreg(nxtarg(0)));
+	if(EQ(a, "-f")){
+		b = nxtarg(0);
+		return(eval && isreg(b));
+	}
 
-	if(EQ(a, "-d"))
-		return(isdir(nxtarg(0)));
+	if(EQ(a, "-d")){
+		b = nxtarg(0);
+		return(eval && isdir(b));
+	}
 
-	if(EQ(a, "-r"))
-		return(tio(nxtarg(0), AREAD));
+	if(EQ(a, "-r")){
+		b = nxtarg(0);
+		return(eval && tio(b, AREAD));
+	}
 
-	if(EQ(a, "-w"))
-		return(tio(nxtarg(0), AWRITE));
+	if(EQ(a, "-w")){
+		b = nxtarg(0);
+		return(eval && tio(b, AWRITE));
+	}
 
-	if(EQ(a, "-x"))
-		return(tio(nxtarg(0), AEXEC));
+	if(EQ(a, "-x")){
+		b = nxtarg(0);
+		return(eval && tio(b, AEXEC));
+	}
 
-	if(EQ(a, "-e"))
-		return(tio(nxtarg(0), AEXIST));
+	if(EQ(a, "-e")){
+		b = nxtarg(0);
+		return(eval && tio(b, AEXIST));
+	}
 
 	if(EQ(a, "-c"))
 		return(0);
@@ -166,14 +212,16 @@
 	if(EQ(a, "-g"))
 		return(0);
 
-	if(EQ(a, "-s"))
-		return(fsizep(nxtarg(0)));
+	if(EQ(a, "-s")){
+		b = nxtarg(0);
+		return(eval && fsizep(b));
+	}
 
 	if(EQ(a, "-t"))
 		if(ap>=ac)
-			return(isatty(1));
+			return(eval && isatty(1));
 		else if(nxtintarg(&int1))
-			return(isatty(int1));
+			return(eval && isatty(int1));
 		else
 			synbad("not a valid file descriptor number ", "");
 
@@ -191,35 +239,40 @@
 	if(EQ(p2, "!="))
 		return(!EQ(nxtarg(0), a));
 
-	if(EQ(p2, "-older"))
-		return(isolder(nxtarg(0), a));
+	if(EQ(p2, "-older")){
+		b = nxtarg(0);
+		return(eval && isolder(b, a));
+	}
 
-	if(EQ(p2, "-ot"))
-		return(isolderthan(nxtarg(0), a));
+	if(EQ(p2, "-ot")){
+		b = nxtarg(0);
+		return(eval && isolderthan(b, a));
+	}
 
-	if(EQ(p2, "-nt"))
-		return(isnewerthan(nxtarg(0), a));
-
-	if(!isint(a, &int1))
-		synbad("unexpected operator/operand: ", p2);
-
-	if(nxtintarg(&int2)){
-		if(EQ(p2, "-eq"))
-			return(int1==int2);
-		if(EQ(p2, "-ne"))
-			return(int1!=int2);
-		if(EQ(p2, "-gt"))
-			return(int1>int2);
-		if(EQ(p2, "-lt"))
-			return(int1<int2);
-		if(EQ(p2, "-ge"))
-			return(int1>=int2);
-		if(EQ(p2, "-le"))
-			return(int1<=int2);
+	if(EQ(p2, "-nt")){
+		b = nxtarg(0);
+		return(eval && isnewerthan(b, a));
 	}
 
-	synbad("unknown operator ",p2);
-	return 0;		/* to shut ken up */
+	if(isint(a, &int1)){
+		if(nxtintarg(&int2)){
+			if(EQ(p2, "-eq"))
+				return(int1==int2);
+			if(EQ(p2, "-ne"))
+				return(int1!=int2);
+			if(EQ(p2, "-gt"))
+				return(int1>int2);
+			if(EQ(p2, "-lt"))
+				return(int1<int2);
+			if(EQ(p2, "-ge"))
+				return(int1>=int2);
+			if(EQ(p2, "-le"))
+				return(int1<=int2);
+			ap--;
+		}
+	}
+	ap--;
+	return !EQ(a, "");
 }
 
 int