v,ast,fmt,parser: support @[tag] for hash statements, like #define and #flag

cmd/tools/vast/vast.v

@@ -592,7 +592,7 @@ fn (t Tree) fn_decl(node ast.FnDecl) &Node {
 	obj.add_terse('return_type', t.type_node(node.return_type))
 	obj.add('source_file', t.number_node(int(node.source_file)))
 	obj.add('scope', t.number_node(int(node.scope)))
-	obj.add('attrs', t.array_node_attr(node.attrs))
+	obj.add_terse('attrs', t.array_node_attr(node.attrs))
 	obj.add_terse('params', t.array_node_arg(node.params))
 	obj.add_terse('generic_names', t.array_node_string(node.generic_names))
 	obj.add_terse('stmts', t.array_node_stmt(node.stmts))
@@ -756,8 +756,10 @@ fn (t Tree) hash_stmt(node ast.HashStmt) &Node {
 	obj.add_terse('kind', t.string_node(node.kind))
 	obj.add_terse('main', t.string_node(node.main))
 	obj.add_terse('msg', t.string_node(node.msg))
+	obj.add_terse('is_use_once', t.bool_node(node.is_use_once))
 	obj.add_terse('ct_conds', t.array_node_expr(node.ct_conds))
 	obj.add_terse('source_file', t.string_node(node.source_file))
+	obj.add_terse('attrs', t.array_node_attr(node.attrs))
 	obj.add('pos', t.pos(node.pos))
 	return obj
 }
@@ -778,11 +780,11 @@ fn (t Tree) global_decl(node ast.GlobalDecl) &Node {
 	mut obj := new_object()
 	obj.add_terse('ast_type', t.string_node('GlobalDecl'))
 	obj.add_terse('mod', t.string_node(node.mod))
-	obj.add('pos', t.pos(node.pos))
+	obj.add_terse('attrs', t.array_node_attr(node.attrs))
 	obj.add_terse('is_block', t.bool_node(node.is_block))
 	obj.add_terse('fields', t.array_node_global_field(node.fields))
+	obj.add('pos', t.pos(node.pos))
 	obj.add('end_comments', t.array_node_comment(node.end_comments))
-	obj.add('attrs', t.array_node_attr(node.attrs))
 	return obj
 }
 

vlib/fontstash/fontstash.c.v

@@ -1,6 +1,8 @@
 module fontstash
 
 #flag -I @VEXEROOT/thirdparty/fontstash
+
+@[use_once]
 #define FONTSTASH_IMPLEMENTATION
 $if gcboehm ? {
 	#define FONTSTASH_MALLOC GC_MALLOC

vlib/sokol/audio/audio.c.v

@@ -10,6 +10,8 @@ $if linux {
 #flag -I @VEXEROOT/thirdparty/sokol
 // FreeBSD requires the audio/alsa-lib to be installed
 #flag freebsd -I/usr/local/include
+
+@[use_once]
 #define SOKOL_IMPL
 #include "sokol_audio.h"
 #flag linux -lasound -lpthread

vlib/sokol/c/declaration.c.v

@@ -56,6 +56,8 @@ $if emscripten ? {
 //#flag windows -DSOKOL_D3D11
 // for simplicity, all header includes are here because import order matters and we dont have any way
 // to ensure import order with V yet
+
+@[use_once]
 #define SOKOL_IMPL
 // TODO: should not be defined for android graphic (apk/aab using sokol) builds, but we have no ways to undefine
 //#define SOKOL_NO_ENTRY
@@ -75,9 +77,13 @@ $if emscripten ? {
 $if !no_sokol_app ? {
 	#include "sokol_app.h"
 }
+
+@[use_once]
 #define SOKOL_IMPL
 #define SOKOL_NO_DEPRECATED
 #include "sokol_gfx.h"
+
+@[use_once]
 #define SOKOL_GL_IMPL
 #include "util/sokol_gl.h"
 #include "sokol_v.post.h"

vlib/sokol/f/f.v

@@ -7,5 +7,6 @@ import sokol.c as _
 
 //#include "ft2build.h"
 
+@[use_once]
 #define SOKOL_FONTSTASH_IMPL
 #include "util/sokol_fontstash.h"

vlib/v/ast/ast.v

@@ -1365,13 +1365,15 @@ pub:
 	mod         string
 	pos         token.Pos
 	source_file string
+	is_use_once bool // true for @[use_once]
 pub mut:
 	val      string // example: 'include <openssl/rand.h> # please install openssl // comment'
 	kind     string // : 'include'
 	main     string // : '<openssl/rand.h>'
 	msg      string // : 'please install openssl'
 	ct_conds []Expr // *all* comptime conditions, that must be true, for the hash to be processed
 	// ct_conds is filled by the checker, based on the current nesting of `$if cond1 {}` blocks
+	attrs []Attr
 }
 
 // variable assign statement

vlib/v/fmt/fmt.v

@@ -1361,6 +1361,7 @@ pub fn (mut f Fmt) goto_stmt(node ast.GotoStmt) {
 }
 
 pub fn (mut f Fmt) hash_stmt(node ast.HashStmt) {
+	f.attrs(node.attrs)
 	f.writeln('#${node.val}')
 }
 

vlib/v/fmt/tests/hashstmt_keep.vv

@@ -10,3 +10,9 @@
 // comment between without newlines
 #include "sqlite3.h"
 // comment directly after the HsahStmt
+
+@[another; use_once]
+#define SOME_SINGLE_HEADER_IMPL 1
+
+@[custom_tag; use_once]
+#flag -I @VMODROOT/c/something/else

vlib/v/parser/comptime.v

@@ -78,6 +78,7 @@ fn (mut p Parser) hash() ast.HashStmt {
 	pos := p.tok.pos()
 	val := p.tok.lit
 	kind := val.all_before(' ')
+	attrs := p.attrs
 	p.next()
 	mut main_str := ''
 	mut msg := ''
@@ -89,6 +90,15 @@ fn (mut p Parser) hash() ast.HashStmt {
 		main_str = content.trim_space()
 		msg = ''
 	}
+
+	mut is_use_once := false
+	for fna in attrs {
+		match fna.name {
+			'use_once' { is_use_once = true }
+			else {}
+		}
+	}
+
 	return ast.HashStmt{
 		mod:         p.mod
 		source_file: p.file_path
@@ -97,6 +107,8 @@ fn (mut p Parser) hash() ast.HashStmt {
 		main:        main_str
 		msg:         msg
 		pos:         pos
+		attrs:       attrs
+		is_use_once: is_use_once
 	}
 }
 

vlib/v/parser/fn.v

@@ -203,7 +203,9 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	mut is_markused := false
 	mut is_expand_simple_interpolation := false
 	mut comments := []ast.Comment{}
-	for fna in p.attrs {
+	fn_attrs := p.attrs
+	p.attrs = []
+	for fna in fn_attrs {
 		match fna.name {
 			'noreturn' {
 				is_noreturn = true
@@ -271,7 +273,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			else {}
 		}
 	}
-	conditional_ctdefine_idx := p.attrs.find_comptime_define() or { -1 }
+	conditional_ctdefine_idx := fn_attrs.find_comptime_define() or { -1 }
 	is_pub := p.tok.kind == .key_pub
 	if is_pub {
 		p.next()
@@ -286,7 +288,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	mut language := p.parse_language()
 	p.fn_language = language
 	if language != .v {
-		for fna in p.attrs {
+		for fna in fn_attrs {
 			if fna.name == 'export' {
 				p.error_with_pos('interop function cannot be exported', fna.pos)
 				break
@@ -555,7 +557,7 @@ run them via `v file.v` instead',
 			is_method:     true
 			receiver_type: rec.typ
 			//
-			attrs:          p.attrs
+			attrs:          fn_attrs
 			is_conditional: conditional_ctdefine_idx != ast.invalid_type_idx
 			ctdefine_idx:   conditional_ctdefine_idx
 			//
@@ -611,7 +613,7 @@ run them via `v file.v` instead',
 			receiver_type:         if is_static_type_method { rec.typ } else { 0 } // used only if is static type method
 			is_file_translated:    p.is_translated
 			//
-			attrs:          p.attrs
+			attrs:          fn_attrs
 			is_conditional: conditional_ctdefine_idx != ast.invalid_type_idx
 			ctdefine_idx:   conditional_ctdefine_idx
 			//
@@ -686,7 +688,7 @@ run them via `v file.v` instead',
 		is_markused:        is_markused
 		is_file_translated: p.is_translated
 		//
-		attrs:          p.attrs
+		attrs:          fn_attrs
 		is_conditional: conditional_ctdefine_idx != ast.invalid_type_idx
 		ctdefine_idx:   conditional_ctdefine_idx
 		//