checker: add pkgconfig to comptime if (#10692)

doc/docs.md

@@ -4017,6 +4017,18 @@ If no flags are passed it will add `--cflags` and `--libs`, both lines below do
 The `.pc` files are looked up into a hardcoded list of default pkg-config paths, the user can add
 extra paths by using the `PKG_CONFIG_PATH` environment variable. Multiple modules can be passed.
 
+To check the existance of a pkg-config use `$pkgconfig('pkg')` as a compile time if condition to 
+check if a pkg-config exists. If it exists the branch will be created. Use `$else` or `$else $if`
+to handle other cases.
+
+```v ignore
+$if $pkgconfig('mysqlclient') {
+	#pkgconfig mysqlclient
+} $else $if $pkgconfig('mariadb') {
+	#pkgconfig mariadb
+}
+```
+
 ### Including C code
 
 You can also include C code directly in your V module.

vlib/v/ast/ast.v

@@ -731,8 +731,9 @@ pub:
 	body_pos token.Position
 	comments []Comment
 pub mut:
-	stmts []Stmt
-	scope &Scope
+	pkg_exist bool
+	stmts     []Stmt
+	scope     &Scope
 }
 
 pub struct UnsafeExpr {
@@ -1439,6 +1440,8 @@ pub:
 	//
 	is_env  bool
 	env_pos token.Position
+	//
+	is_pkgconfig bool
 pub mut:
 	sym         TypeSymbol
 	result_type Type

vlib/v/checker/checker.v

@@ -6185,6 +6185,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 		if !node.has_else || i < node.branches.len - 1 {
 			if node.is_comptime {
 				should_skip = c.comp_if_branch(branch.cond, branch.pos)
+				node.branches[i].pkg_exist = !should_skip
 			} else {
 				// check condition type is boolean
 				c.expected_type = ast.bool_type
@@ -6514,6 +6515,15 @@ fn (mut c Checker) comp_if_branch(cond ast.Expr, pos token.Position) bool {
 				return !(expr as ast.BoolLiteral).val
 			}
 		}
+		ast.ComptimeCall {
+			if cond.is_pkgconfig {
+				mut m := pkgconfig.main([cond.args_var]) or {
+					c.error(err.msg, cond.pos)
+					return true
+				}
+				m.run() or { return true }
+			}
+		}
 		else {
 			c.error('invalid `\$if` condition', pos)
 		}

vlib/v/fmt/fmt.v

@@ -1764,6 +1764,8 @@ pub fn (mut f Fmt) comptime_call(node ast.ComptimeCall) {
 			f.write("\$embed_file('$node.embed_file.rpath')")
 		} else if node.is_env {
 			f.write("\$env('$node.args_var')")
+		} else if node.is_pkgconfig {
+			f.write("\$pkgconfig('$node.args_var')")
 		} else {
 			inner_args := if node.args_var != '' {
 				node.args_var

vlib/v/gen/c/comptime.v

@@ -232,7 +232,7 @@ fn (mut g Gen) comp_if(node ast.IfExpr) {
 			} else {
 				g.write('#elif ')
 			}
-			comp_if_stmts_skip = !g.comp_if_cond(branch.cond)
+			comp_if_stmts_skip = !g.comp_if_cond(branch.cond, branch.pkg_exist)
 			g.writeln('')
 		}
 		expr_str := g.out.last_n(g.out.len - start_pos).trim_space()
@@ -280,7 +280,7 @@ fn (mut g Gen) comp_if(node ast.IfExpr) {
 // returning `false` means the statements inside the $if can be skipped
 */
 // returns the value of the bool comptime expression
-fn (mut g Gen) comp_if_cond(cond ast.Expr) bool {
+fn (mut g Gen) comp_if_cond(cond ast.Expr, pkg_exist bool) bool {
 	match cond {
 		ast.BoolLiteral {
 			g.expr(cond)
@@ -288,13 +288,13 @@ fn (mut g Gen) comp_if_cond(cond ast.Expr) bool {
 		}
 		ast.ParExpr {
 			g.write('(')
-			is_cond_true := g.comp_if_cond(cond.expr)
+			is_cond_true := g.comp_if_cond(cond.expr, pkg_exist)
 			g.write(')')
 			return is_cond_true
 		}
 		ast.PrefixExpr {
 			g.write(cond.op.str())
-			return g.comp_if_cond(cond.right)
+			return g.comp_if_cond(cond.right, pkg_exist)
 		}
 		ast.PostfixExpr {
 			ifdef := g.comp_if_to_ifdef((cond.expr as ast.Ident).name, true) or {
@@ -307,9 +307,9 @@ fn (mut g Gen) comp_if_cond(cond ast.Expr) bool {
 		ast.InfixExpr {
 			match cond.op {
 				.and, .logical_or {
-					l := g.comp_if_cond(cond.left)
+					l := g.comp_if_cond(cond.left, pkg_exist)
 					g.write(' $cond.op ')
-					r := g.comp_if_cond(cond.right)
+					r := g.comp_if_cond(cond.right, pkg_exist)
 					return if cond.op == .and { l && r } else { l || r }
 				}
 				.key_is, .not_is {
@@ -381,6 +381,10 @@ fn (mut g Gen) comp_if_cond(cond ast.Expr) bool {
 			g.write('defined($ifdef)')
 			return true
 		}
+		ast.ComptimeCall {
+			g.write('$pkg_exist')
+			return true
+		}
 		else {
 			// should be unreachable, but just in case
 			g.write('1')

vlib/v/parser/comptime.v

@@ -9,7 +9,7 @@ import v.pref
 import v.token
 
 const (
-	supported_comptime_calls = ['html', 'tmpl', 'env', 'embed_file']
+	supported_comptime_calls = ['html', 'tmpl', 'env', 'embed_file', 'pkgconfig']
 )
 
 // // #include, #flag, #v
@@ -45,7 +45,7 @@ fn (mut p Parser) comp_call() ast.ComptimeCall {
 	}
 	p.check(.dollar)
 	start_pos := p.prev_tok.position()
-	error_msg := 'only `\$tmpl()`, `\$env()`, `\$embed_file()` and `\$vweb.html()` comptime functions are supported right now'
+	error_msg := 'only `\$tmpl()`, `\$env()`, `\$embed_file()`, `\$pkgconfig()` and `\$vweb.html()` comptime functions are supported right now'
 	if p.peek_tok.kind == .dot {
 		n := p.check_name() // skip `vweb.html()` TODO
 		if n != 'vweb' {
@@ -62,9 +62,9 @@ fn (mut p Parser) comp_call() ast.ComptimeCall {
 	is_embed_file := n == 'embed_file'
 	is_html := n == 'html'
 	// $env('ENV_VAR_NAME')
+	p.check(.lpar)
+	spos := p.tok.position()
 	if n == 'env' {
-		p.check(.lpar)
-		spos := p.tok.position()
 		s := p.tok.lit
 		p.check(.string)
 		p.check(.rpar)
@@ -77,8 +77,19 @@ fn (mut p Parser) comp_call() ast.ComptimeCall {
 			pos: spos.extend(p.prev_tok.position())
 		}
 	}
-	p.check(.lpar)
-	spos := p.tok.position()
+	if n == 'pkgconfig' {
+		s := p.tok.lit
+		p.check(.string)
+		p.check(.rpar)
+		return ast.ComptimeCall{
+			scope: 0
+			method_name: n
+			args_var: s
+			is_pkgconfig: true
+			env_pos: spos
+			pos: spos.extend(p.prev_tok.position())
+		}
+	}
 	literal_string_param := if is_html { '' } else { p.tok.lit }
 	path_of_literal_string_param := literal_string_param.replace('/', os.path_separator)
 	if !is_html {

vlib/v/tests/comptime_if_pkgconfig_test.v

@@ -0,0 +1,10 @@
+fn test_comptime_pkgconfig() {
+	$if $pkgconfig('mysqlclient') {
+		assert true
+		return
+	} $else {
+		assert true
+		return
+	}
+	assert false
+}