lix/src/libexpr/parser.y

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%glr-parser
%pure-parser
%locations
%error-verbose
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%defines
/* %no-lines */
%parse-param { yyscan_t scanner }
%parse-param { ParseData * data }
%lex-param { yyscan_t scanner }
%{
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/* Newer versions of Bison copy the declarations below to
parser-tab.hh, which sucks bigtime since lexer.l doesn't want that
stuff. So allow it to be excluded. */
#ifndef BISON_HEADER_HACK
#define BISON_HEADER_HACK
#include "util.hh"
#include "nixexpr.hh"
#include "parser-tab.hh"
#include "lexer-tab.hh"
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#define YYSTYPE YYSTYPE // workaround a bug in Bison 2.4
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace nix;
namespace nix {
struct ParseData
{
SymbolTable & symbols;
Expr * result;
Path basePath;
Path path;
string error;
Symbol sLetBody;
ParseData(SymbolTable & symbols)
: symbols(symbols)
, sLetBody(symbols.create("<let-body>"))
{ };
};
static string showAttrPath(const vector<Symbol> & attrPath)
{
string s;
foreach (vector<Symbol>::const_iterator, i, attrPath) {
if (!s.empty()) s += '.';
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s += *i;
}
return s;
}
static void dupAttr(const vector<Symbol> & attrPath, const Pos & pos, const Pos & prevPos)
{
throw ParseError(format("attribute `%1%' at %2% already defined at %3%")
% showAttrPath(attrPath) % pos % prevPos);
}
static void dupAttr(Symbol attr, const Pos & pos, const Pos & prevPos)
{
vector<Symbol> attrPath; attrPath.push_back(attr);
throw ParseError(format("attribute `%1%' at %2% already defined at %3%")
% showAttrPath(attrPath) % pos % prevPos);
}
static void addAttr(ExprAttrs * attrs, const vector<Symbol> & attrPath,
Expr * e, const Pos & pos)
{
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unsigned int n = 0;
foreach (vector<Symbol>::const_iterator, i, attrPath) {
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n++;
ExprAttrs::Attrs::iterator j = attrs->attrs.find(*i);
if (j != attrs->attrs.end()) {
ExprAttrs * attrs2 = dynamic_cast<ExprAttrs *>(j->second.first);
if (!attrs2 || n == attrPath.size()) dupAttr(attrPath, pos, j->second.second);
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attrs = attrs2;
} else {
if (attrs->attrNames.find(*i) != attrs->attrNames.end())
dupAttr(attrPath, pos, attrs->attrNames[*i]);
attrs->attrNames[*i] = pos;
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if (n == attrPath.size())
attrs->attrs[*i] = ExprAttrs::Attr(e, pos);
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else {
ExprAttrs * nested = new ExprAttrs;
attrs->attrs[*i] = ExprAttrs::Attr(nested, pos);
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attrs = nested;
}
}
}
}
static void addFormal(const Pos & pos, Formals * formals, const Formal & formal)
{
if (formals->argNames.find(formal.name) != formals->argNames.end())
throw ParseError(format("duplicate formal function argument `%1%' at %2%")
% formal.name % pos);
formals->formals.push_front(formal);
formals->argNames.insert(formal.name);
}
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static Expr * stripIndentation(vector<Expr *> & es)
{
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if (es.empty()) return new ExprString("");
/* Figure out the minimum indentation. Note that by design
whitespace-only final lines are not taken into account. (So
the " " in "\n ''" is ignored, but the " " in "\n foo''" is.) */
bool atStartOfLine = true; /* = seen only whitespace in the current line */
unsigned int minIndent = 1000000;
unsigned int curIndent = 0;
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foreach (vector<Expr *>::iterator, i, es) {
ExprIndStr * e = dynamic_cast<ExprIndStr *>(*i);
if (!e) {
/* Anti-quotations end the current start-of-line whitespace. */
if (atStartOfLine) {
atStartOfLine = false;
if (curIndent < minIndent) minIndent = curIndent;
}
continue;
}
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for (unsigned int j = 0; j < e->s.size(); ++j) {
if (atStartOfLine) {
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if (e->s[j] == ' ')
curIndent++;
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else if (e->s[j] == '\n') {
/* Empty line, doesn't influence minimum
indentation. */
curIndent = 0;
} else {
atStartOfLine = false;
if (curIndent < minIndent) minIndent = curIndent;
}
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} else if (e->s[j] == '\n') {
atStartOfLine = true;
curIndent = 0;
}
}
}
/* Strip spaces from each line. */
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vector<Expr *> * es2 = new vector<Expr *>;
atStartOfLine = true;
unsigned int curDropped = 0;
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unsigned int n = es.size();
for (vector<Expr *>::iterator i = es.begin(); i != es.end(); ++i, --n) {
ExprIndStr * e = dynamic_cast<ExprIndStr *>(*i);
if (!e) {
atStartOfLine = false;
curDropped = 0;
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es2->push_back(*i);
continue;
}
string s2;
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for (unsigned int j = 0; j < e->s.size(); ++j) {
if (atStartOfLine) {
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if (e->s[j] == ' ') {
if (curDropped++ >= minIndent)
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s2 += e->s[j];
}
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else if (e->s[j] == '\n') {
curDropped = 0;
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s2 += e->s[j];
} else {
atStartOfLine = false;
curDropped = 0;
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s2 += e->s[j];
}
} else {
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s2 += e->s[j];
if (e->s[j] == '\n') atStartOfLine = true;
}
}
/* Remove the last line if it is empty and consists only of
spaces. */
if (n == 1) {
string::size_type p = s2.find_last_of('\n');
if (p != string::npos && s2.find_first_not_of(' ', p + 1) == string::npos)
s2 = string(s2, 0, p + 1);
}
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es2->push_back(new ExprString(s2));
}
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return new ExprConcatStrings(es2);
}
void backToString(yyscan_t scanner);
void backToIndString(yyscan_t scanner);
static Pos makeCurPos(const YYLTYPE & loc, ParseData * data)
{
return Pos(data->path, loc.first_line, loc.first_column);
}
#define CUR_POS makeCurPos(*yylocp, data)
}
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void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * error)
{
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data->error = (format("%1%, at %2%")
% error % makeCurPos(*loc, data)).str();
}
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#endif
%}
%union {
nix::Expr * e;
nix::ExprList * list;
nix::ExprAttrs * attrs;
nix::Formals * formals;
nix::Formal * formal;
int n;
char * id; // !!! -> Symbol
char * path;
char * uri;
std::vector<nix::Symbol> * ids;
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std::vector<nix::Expr *> * string_parts;
}
%type <e> start expr expr_function expr_if expr_op
%type <e> expr_app expr_select expr_simple
%type <list> expr_list
%type <attrs> binds
%type <formals> formals
%type <formal> formal
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%type <ids> ids attrpath
%type <string_parts> string_parts ind_string_parts
%token <id> ID ATTRPATH
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%token <e> STR IND_STR
%token <n> INT
%token <path> PATH
%token <uri> URI
%token IF THEN ELSE ASSERT WITH LET IN REC INHERIT EQ NEQ AND OR IMPL
%token DOLLAR_CURLY /* == ${ */
%token IND_STRING_OPEN IND_STRING_CLOSE
%token ELLIPSIS
%nonassoc IMPL
%left OR
%left AND
%nonassoc EQ NEQ
%right UPDATE
%left NEG
%left '+'
%right CONCAT
%nonassoc '?'
%nonassoc '~'
%%
start: expr { data->result = $1; };
expr: expr_function;
expr_function
: ID ':' expr_function
{ $$ = new ExprLambda(CUR_POS, data->symbols.create($1), false, 0, $3); }
| '{' formals '}' ':' expr_function
{ $$ = new ExprLambda(CUR_POS, data->symbols.create(""), true, $2, $5); }
| '{' formals '}' '@' ID ':' expr_function
{ $$ = new ExprLambda(CUR_POS, data->symbols.create($5), true, $2, $7); }
| ID '@' '{' formals '}' ':' expr_function
{ $$ = new ExprLambda(CUR_POS, data->symbols.create($1), true, $4, $7); }
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| ASSERT expr ';' expr_function
{ $$ = new ExprAssert(CUR_POS, $2, $4); }
| WITH expr ';' expr_function
{ $$ = new ExprWith(CUR_POS, $2, $4); }
| LET binds IN expr_function
{ $$ = new ExprLet($2, $4); }
| expr_if
;
expr_if
: IF expr THEN expr ELSE expr { $$ = new ExprIf($2, $4, $6); }
| expr_op
;
expr_op
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: '!' expr_op %prec NEG { $$ = new ExprOpNot($2); }
| expr_op EQ expr_op { $$ = new ExprOpEq($1, $3); }
| expr_op NEQ expr_op { $$ = new ExprOpNEq($1, $3); }
| expr_op AND expr_op { $$ = new ExprOpAnd($1, $3); }
| expr_op OR expr_op { $$ = new ExprOpOr($1, $3); }
| expr_op IMPL expr_op { $$ = new ExprOpImpl($1, $3); }
| expr_op UPDATE expr_op { $$ = new ExprOpUpdate($1, $3); }
| expr_op '?' ID { $$ = new ExprOpHasAttr($1, data->symbols.create($3)); }
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| expr_op '+' expr_op
{ vector<Expr *> * l = new vector<Expr *>;
l->push_back($1);
l->push_back($3);
$$ = new ExprConcatStrings(l);
}
| expr_op CONCAT expr_op { $$ = new ExprOpConcatLists($1, $3); }
| expr_app
;
expr_app
: expr_app expr_select
{ $$ = new ExprApp($1, $2); }
| expr_select { $$ = $1; }
;
expr_select
: expr_select '.' ID
{ $$ = new ExprSelect($1, data->symbols.create($3)); }
| expr_simple { $$ = $1; }
;
expr_simple
: ID { $$ = new ExprVar(data->symbols.create($1)); }
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| INT { $$ = new ExprInt($1); }
| '"' string_parts '"' {
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/* For efficiency, and to simplify parse trees a bit. */
if ($2->empty()) $$ = new ExprString("");
else if ($2->size() == 1) $$ = $2->front();
else $$ = new ExprConcatStrings($2);
}
| IND_STRING_OPEN ind_string_parts IND_STRING_CLOSE {
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$$ = stripIndentation(*$2);
}
| PATH { $$ = new ExprPath(absPath($1, data->basePath)); }
| URI { $$ = new ExprString($1); }
| '(' expr ')' { $$ = $2; }
/* Let expressions `let {..., body = ...}' are just desugared
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into `(rec {..., body = ...}).body'. */
| LET '{' binds '}'
{ $3->recursive = true; $$ = new ExprSelect($3, data->symbols.create("body")); }
| REC '{' binds '}'
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{ $3->recursive = true; $$ = $3; }
| '{' binds '}'
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{ $$ = $2; }
| '[' expr_list ']' { $$ = $2; }
;
string_parts
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: string_parts STR { $$ = $1; $1->push_back($2); }
| string_parts DOLLAR_CURLY expr '}' { backToString(scanner); $$ = $1; $1->push_back($3); }
| { $$ = new vector<Expr *>; }
;
ind_string_parts
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: ind_string_parts IND_STR { $$ = $1; $1->push_back($2); }
| ind_string_parts DOLLAR_CURLY expr '}' { backToIndString(scanner); $$ = $1; $1->push_back($3); }
| { $$ = new vector<Expr *>; }
;
binds
: binds attrpath '=' expr ';' { $$ = $1; addAttr($$, *$2, $4, makeCurPos(@2, data)); }
| binds INHERIT ids ';'
{ $$ = $1;
foreach (vector<Symbol>::iterator, i, *$3) {
if ($$->attrNames.find(*i) != $$->attrNames.end())
dupAttr(*i, makeCurPos(@3, data), $$->attrNames[*i]);
Pos pos = makeCurPos(@3, data);
$$->inherited.push_back(ExprAttrs::Inherited(*i, pos));
$$->attrNames[*i] = pos;
}
}
| binds INHERIT '(' expr ')' ids ';'
{ $$ = $1;
/* !!! Should ensure sharing of the expression in $4. */
foreach (vector<Symbol>::iterator, i, *$6) {
if ($$->attrNames.find(*i) != $$->attrNames.end())
dupAttr(*i, makeCurPos(@6, data), $$->attrNames[*i]);
$$->attrs[*i] = ExprAttrs::Attr(new ExprSelect($4, *i), makeCurPos(@6, data));
$$->attrNames[*i] = makeCurPos(@6, data);
}}
| { $$ = new ExprAttrs; }
;
ids
: ids ID { $$ = $1; $1->push_back(data->symbols.create($2)); /* !!! dangerous */ }
| { $$ = new vector<Symbol>; }
;
attrpath
: attrpath '.' ID { $$ = $1; $1->push_back(data->symbols.create($3)); }
| ID { $$ = new vector<Symbol>; $$->push_back(data->symbols.create($1)); }
;
expr_list
: expr_list expr_select { $$ = $1; $1->elems.push_back($2); /* !!! dangerous */ }
| { $$ = new ExprList; }
;
formals
: formal ',' formals
{ $$ = $3; addFormal(CUR_POS, $$, *$1); }
| formal
{ $$ = new Formals; addFormal(CUR_POS, $$, *$1); $$->ellipsis = false; }
|
{ $$ = new Formals; $$->ellipsis = false; }
| ELLIPSIS
{ $$ = new Formals; $$->ellipsis = true; }
;
formal
: ID { $$ = new Formal(data->symbols.create($1), 0); }
| ID '?' expr { $$ = new Formal(data->symbols.create($1), $3); }
;
%%
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <eval.hh>
namespace nix {
static Expr * parse(EvalState & state, const char * text,
const Path & path, const Path & basePath)
{
yyscan_t scanner;
ParseData data(state.symbols);
data.basePath = basePath;
data.path = path;
yylex_init(&scanner);
yy_scan_string(text, scanner);
int res = yyparse(scanner, &data);
yylex_destroy(scanner);
if (res) throw ParseError(data.error);
try {
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data.result->bindVars(state.staticBaseEnv);
} catch (Error & e) {
throw ParseError(format("%1%, in `%2%'") % e.msg() % path);
}
return data.result;
}
Expr * parseExprFromFile(EvalState & state, Path path)
{
assert(path[0] == '/');
/* If `path' is a symlink, follow it. This is so that relative
path references work. */
struct stat st;
while (true) {
if (lstat(path.c_str(), &st))
throw SysError(format("getting status of `%1%'") % path);
if (!S_ISLNK(st.st_mode)) break;
path = absPath(readLink(path), dirOf(path));
}
/* If `path' refers to a directory, append `/default.nix'. */
if (S_ISDIR(st.st_mode))
path = canonPath(path + "/default.nix");
/* Read and parse the input file. */
return parse(state, readFile(path).c_str(), path, dirOf(path));
}
Expr * parseExprFromString(EvalState & state,
const string & s, const Path & basePath)
{
return parse(state, s.c_str(), "(string)", basePath);
}
}