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authorBoris Kolpackov <boris@codesynthesis.com>2015-12-03 11:04:48 +0200
committerBoris Kolpackov <boris@codesynthesis.com>2015-12-03 11:08:08 +0200
commit772b1e013bb0068d7347d0bbe2ff73c67358ee1b (patch)
tree8d7bdd8999ed62db77015e60d6115eb6ff235912 /build
parentbecea217436a79b7ef37a023da6cb4c560225a71 (diff)
Implement if-else conditions
if if! elif elif! else The expression should evaluate to true of false. The if! and elif! versions are provided as shortcuts to writing if (!...). See tests/if-else for examples.
Diffstat (limited to 'build')
-rw-r--r--build/parser13
-rw-r--r--build/parser.cxx192
2 files changed, 185 insertions, 20 deletions
diff --git a/build/parser b/build/parser
index 4390c67..ca27890 100644
--- a/build/parser
+++ b/build/parser
@@ -75,6 +75,9 @@ namespace build
define (token&, token_type&);
void
+ if_else (token&, token_type&);
+
+ void
variable (token&, token_type&, std::string name, token_type kind);
std::string
@@ -115,6 +118,16 @@ namespace build
const dir_path* dir,
const std::string* type);
+ // Skip until newline or eos.
+ //
+ void
+ skip_line (token&, token_type&);
+
+ // Skip until block-closing } or eos, taking into account nested blocks.
+ //
+ void
+ skip_block (token&, token_type&);
+
// Buildspec.
//
buildspec
diff --git a/build/parser.cxx b/build/parser.cxx
index ee22254..de4cfdc 100644
--- a/build/parser.cxx
+++ b/build/parser.cxx
@@ -64,7 +64,7 @@ namespace build
}
token parser::
- parse_variable (lexer& l, scope& s, string name, token_type kind)
+ parse_variable (lexer& l, scope& s, string name, type kind)
{
path_ = &l.name ();
lexer_ = &l;
@@ -78,10 +78,16 @@ namespace build
}
void parser::
- clause (token& t, token_type& tt)
+ clause (token& t, type& tt)
{
tracer trace ("parser::clause", &path_);
+ // clause() should always stop at a token that is at the beginning of
+ // the line (except for eof). That is, if something is called to parse
+ // a line, it should parse it until newline (or fail). This is important
+ // for if-else blocks, directory scopes, etc., that assume the } token
+ // they see is on the new line.
+ //
while (tt != type::eos)
{
// We always start with one or more names.
@@ -139,6 +145,20 @@ namespace build
define (t, tt);
continue;
}
+ else if (n == "if" ||
+ n == "if!")
+ {
+ if_else (t, tt);
+ continue;
+ }
+ else if (n == "else" ||
+ n == "elif" ||
+ n == "elif!")
+ {
+ // Valid ones are handled in if_else().
+ //
+ fail (t) << n << " without if";
+ }
}
// ': foo' is equvalent to '{}: foo' and to 'dir{}: foo'.
@@ -466,7 +486,7 @@ namespace build
}
void parser::
- source (token& t, token_type& tt)
+ source (token& t, type& tt)
{
tracer trace ("parser::source", &path_);
@@ -544,7 +564,7 @@ namespace build
}
void parser::
- include (token& t, token_type& tt)
+ include (token& t, type& tt)
{
tracer trace ("parser::include", &path_);
@@ -689,7 +709,7 @@ namespace build
}
void parser::
- import (token& t, token_type& tt)
+ import (token& t, type& tt)
{
tracer trace ("parser::import", &path_);
@@ -705,15 +725,15 @@ namespace build
value* val (nullptr);
const build::variable* var (nullptr);
- token_type at; // Assignment type.
+ type at; // Assignment type.
if (tt == type::name)
{
at = peek ();
- if (at == token_type::equal || at == token_type::plus_equal)
+ if (at == type::equal || at == type::plus_equal)
{
var = &var_pool.find (t.value);
- val = at == token_type::equal
+ val = at == type::equal
? &scope_->assign (*var)
: &scope_->append (*var);
next (t, tt); // Consume =/+=.
@@ -738,7 +758,7 @@ namespace build
if (val != nullptr)
{
- if (at == token_type::equal)
+ if (at == type::equal)
val->assign (move (r), *var);
else
val->append (move (r), *var);
@@ -752,7 +772,7 @@ namespace build
}
void parser::
- export_ (token& t, token_type& tt)
+ export_ (token& t, type& tt)
{
tracer trace ("parser::export", &path_);
@@ -779,7 +799,7 @@ namespace build
}
void parser::
- using_ (token& t, token_type& tt)
+ using_ (token& t, type& tt)
{
tracer trace ("parser::using", &path_);
@@ -821,7 +841,7 @@ namespace build
constexpr const char derived_ext_var[] = "extension";
void parser::
- define (token& t, token_type& tt)
+ define (token& t, type& tt)
{
// define <derived>: <base>
//
@@ -883,7 +903,102 @@ namespace build
}
void parser::
- print (token& t, token_type& tt)
+ if_else (token& t, type& tt)
+ {
+ // Handle the whole if-else chain. See tests/if-else.
+ //
+ bool taken (false); // One of the branches has been taken.
+
+ for (;;)
+ {
+ string k (move (t.value));
+ next (t, tt);
+
+ bool take (false); // Take this branch?
+
+ if (k != "else")
+ {
+ // Should we evaluate the expression if one of the branches has
+ // already been taken? On the one hand, evaluating it is a waste
+ // of time. On the other, it can be invalid and the only way for
+ // the user to know their buildfile is valid is to test every
+ // branch. There could also be side effects. We also have the same
+ // problem with ignored branch blocks except there evaluating it
+ // is not an option. So let's skip it.
+ //
+ if (taken)
+ skip_line (t, tt);
+ else
+ {
+ if (tt == type::newline || tt == type::eos)
+ fail (t) << "expected " << k << "-expression instead of " << t;
+
+ // Parse as names to get variable expansion, evaluation, etc.
+ //
+ const location nsl (get_location (t, &path_));
+ names_type ns (names (t, tt));
+
+ // Should evaluate to true or false.
+ //
+ if (ns.size () != 1 || !value_traits<bool>::assign (ns[0]))
+ fail (nsl) << "expected " << k << "-expression to evaluate to "
+ << "'true' or 'false' instead of '" << ns << "'";
+
+ bool e (ns[0].value == "true");
+ take = (k.back () == '!' ? !e : e);
+ }
+ }
+ else
+ take = !taken;
+
+ if (tt != type::newline)
+ fail (t) << "expected newline instead of " << t << " after " << k
+ << (k != "else" ? "-expression" : "");
+
+ if (next (t, tt) != type::lcbrace)
+ fail (t) << "expected { instead of " << t << " at the beginning of "
+ << k << "-block";
+
+ if (next (t, tt) != type::newline)
+ fail (t) << "expected newline after {";
+
+ next (t, tt);
+
+ if (take)
+ {
+ clause (t, tt);
+ taken = true;
+ }
+ else
+ skip_block (t, tt);
+
+ if (tt != type::rcbrace)
+ fail (t) << "expected } instead of " << t << " at the end of " << k
+ << "-block";
+
+ next (t, tt);
+
+ if (tt == type::newline)
+ next (t, tt);
+ else if (tt != type::eos)
+ fail (t) << "expected newline after }";
+
+ // See if we have another el* keyword.
+ //
+ if (k != "else" && tt == type::name)
+ {
+ const string& n (t.value);
+
+ if (!t.quoted && (n == "else" || n == "elif" || n == "elif!"))
+ continue;
+ }
+
+ break;
+ }
+ }
+
+ void parser::
+ print (token& t, type& tt)
{
// Parse the rest as names to get variable expansion, etc. Switch
// to the variable value lexing mode so that we don't treat special
@@ -920,7 +1035,7 @@ namespace build
}
void parser::
- variable (token& t, token_type& tt, string name, token_type kind)
+ variable (token& t, type& tt, string name, type kind)
{
const auto& var (var_pool.find (move (name)));
names_type vns (variable_value (t, tt, var));
@@ -942,7 +1057,7 @@ namespace build
}
names parser::
- variable_value (token& t, token_type& tt, const variable_type& var)
+ variable_value (token& t, type& tt, const variable_type& var)
{
if (var.pairs != '\0')
lexer_->mode (lexer_mode::pairs, var.pairs);
@@ -956,7 +1071,7 @@ namespace build
}
parser::names_type parser::
- eval (token& t, token_type& tt)
+ eval (token& t, type& tt)
{
lexer_->mode (lexer_mode::eval);
next (t, tt);
@@ -1587,6 +1702,43 @@ namespace build
}
}
+ void parser::
+ skip_line (token& t, type& tt)
+ {
+ for (; tt != type::newline && tt != type::eos; next (t, tt)) ;
+ }
+
+ void parser::
+ skip_block (token& t, type& tt)
+ {
+ // Skip until } or eos, keeping track of the {}-balance.
+ //
+ for (size_t b (0); tt != type::eos; )
+ {
+ if (tt == type::lcbrace || tt == type::rcbrace)
+ {
+ type ptt (peek ());
+ if (ptt == type::newline || ptt == type::eos) // Block { or }.
+ {
+ if (tt == type::lcbrace)
+ ++b;
+ else
+ {
+ if (b == 0)
+ break;
+
+ --b;
+ }
+ }
+ }
+
+ skip_line (t, tt);
+
+ if (tt != type::eos)
+ next (t, tt);
+ }
+ }
+
// Buildspec parsing.
//
@@ -1659,7 +1811,7 @@ namespace build
}
buildspec parser::
- buildspec_clause (token& t, token_type& tt, token_type tt_end)
+ buildspec_clause (token& t, type& tt, type tt_end)
{
buildspec bs;
@@ -1917,8 +2069,8 @@ namespace build
trace);
}
- token_type parser::
- next (token& t, token_type& tt)
+ type parser::
+ next (token& t, type& tt)
{
if (!peeked_)
t = lexer_->next ();
@@ -1932,7 +2084,7 @@ namespace build
return tt;
}
- token_type parser::
+ type parser::
peek ()
{
if (!peeked_)