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rc: read heredoc when receiving '\n' (thanks Eckard Brauer)

Eckard's test case:

cat <<! | cat
asdf
!

The issue is that we have to continue parsing until we see
the '\n' before consuming the here document.

So we revert to the old approach of having two functions:

heredoc() which remembers if we'v seen a heredoc redirection
and a second readhere() function that reads the doc from
the lexers input and sets Tree.str on thee REDIR node.

--- a/sys/src/cmd/rc/fns.h

+++ b/sys/src/cmd/rc/fns.h

@@ -58,7 +58,8 @@

 void	pushlist(void);

 void	pushredir(int, int, int);

 word*	pushword(char*);

-char*	readhere(tree*, io*);

+void	readhere(io*);

+void	heredoc(tree*);

 void	setstatus(char*);

 void	skipnl(void);

 void	start(code*, int, var*, redir*);

--- a/sys/src/cmd/rc/here.c

+++ b/sys/src/cmd/rc/here.c

@@ -6,16 +6,12 @@

 void psubst(io*, unsigned char*);

 void pstrs(io*, word*);

-char*

-readhere(tree *tag, io *in)

+static char*

+readhere1(tree *tag, io *in)

 {

 	io *out;

 	char c, *m;

-	if(tag->type!=WORD){

-		yyerror("Bad here tag");

-		return 0;

-	}

 	pprompt();

 	out = openiostr();

 	m = tag->str;

@@ -45,6 +41,34 @@

 	}

 	doprompt = 1;

 	return closeiostr(out);

+}

+

+static tree *head, *tail;

+

+void

+heredoc(tree *redir)

+{

+	if(redir->child[0]->type!=WORD){

+		yyerror("Bad here tag");

+		return;

+	}

+	redir->child[2]=0;

+	if(head)

+		tail->child[2]=redir;

+	else

+		head=redir;

+	tail=redir;

+}

+

+void

+readhere(io *in)

+{

+	while(head){

+		tail=head->child[2];

+		head->child[2]=0;

+		head->str=readhere1(head->child[0], in);

+		head=tail;

+	}

 }

 void

--- a/sys/src/cmd/rc/syn.y

+++ b/sys/src/cmd/rc/syn.y

@@ -22,7 +22,7 @@

 %type<tree> WORD REDIR DUP PIPE

 %%

 rc:				{ return 1;}

-|	line '\n'		{return !compile($1);}

+|	line '\n'		{readhere(lex->input); return !compile($1);}

 line:	cmd

 |	cmdsa line		{$$=tree2(';', $1, $2);}

 body:	cmd

@@ -30,13 +30,13 @@

 cmdsa:	cmd ';'

 |	cmd '&'			{$$=tree1('&', $1);}

 cmdsan:	cmdsa

-|	cmd '\n'

+|	cmd '\n'		{readhere(lex->input);}

 brace:	'{' body '}'		{$$=tree1(BRACE, $2);}

 paren:	'(' body ')'		{$$=tree1(PCMD, $2);}

 assign:	first '=' word		{$$=tree2('=', $1, $3);}

 epilog:				{$$=0;}

 |	redir epilog		{$$=mung2($1, $1->child[0], $2);}

-redir:	REDIR word		{($$=mung1($1, $2))->str=$1->rtype==HERE?readhere($2,lex->input):0;}

+redir:	REDIR word		{$$=mung1($1, $2); if($$->rtype==HERE) heredoc($$);}

 |	DUP

 cmd:				{$$=0;}

 |	brace epilog		{$$=epimung($1, $2);}