From d24dce8eb33d60395e8dd8326bbfd0e81a0bcf7b Mon Sep 17 00:00:00 2001
From: StunxFS <56417208+StunxFS@users.noreply.github.com>
Date: Mon, 9 May 2022 01:18:26 -0400
Subject: [PATCH] parser,checker: support `$compile_error('message')` and
 `$compile_warn('message')` (#14320)

---
 CHANGELOG.md                           |  1 +
 doc/docs.md                            | 31 +++++++++++++++++++--
 vlib/v/checker/comptime.v              |  7 +++++
 vlib/v/checker/tests/compile_error.out | 14 ++++++++++
 vlib/v/checker/tests/compile_error.vv  | 15 ++++++++++
 vlib/v/parser/comptime.v               | 38 +++++++++-----------------
 6 files changed, 78 insertions(+), 28 deletions(-)
 create mode 100644 vlib/v/checker/tests/compile_error.out
 create mode 100644 vlib/v/checker/tests/compile_error.vv

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b75bbef459..8c8ad94b3e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 -*Not yet released, changelog is not full*
 - Introduce `isize` and `usize` types, deprecate `size_t` in favor of `usize`.
 - Add `datatypes` and `datatypes.fsm` modules.
+- Add `compile_error` and `compile_warn` comptime functions.
 
 -## V 0.2.4
 -*Not yet released, changelog is not full*
diff --git a/doc/docs.md b/doc/docs.md
index f3a60daf07..a9a1480737 100644
--- a/doc/docs.md
+++ b/doc/docs.md
@@ -5433,9 +5433,6 @@ numbers: [1, 2, 3]
 3
 ```
 
-
-
-
 #### `$env`
 
 ```v
@@ -5451,6 +5448,34 @@ V can bring in values at compile time from environment variables.
 `$env('ENV_VAR')` can also be used in top-level `#flag` and `#include` statements:
 `#flag linux -I $env('JAVA_HOME')/include`.
 
+#### `$compile_error` and `$compile_warn`
+
+These two comptime functions are very useful for displaying custom errors/warnings during
+compile time.
+
+Both receive as their only argument a string literal that contains the message to display:
+
+```v failcompile nofmt
+// x.v
+module main
+
+$if linux {
+    $compile_error('Linux is not supported')
+}
+
+fn main() {
+}
+
+$ v run x.v
+x.v:4:5: error: Linux is not supported
+    2 |
+    3 | $if linux {
+    4 |     $compile_error('Linux is not supported')
+      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    5 | }
+    6 |
+```
+
 ### Environment specific files
 
 If a file has an environment-specific suffix, it will only be compiled for that environment.
diff --git a/vlib/v/checker/comptime.v b/vlib/v/checker/comptime.v
index 0175364894..7dfab0c4e5 100644
--- a/vlib/v/checker/comptime.v
+++ b/vlib/v/checker/comptime.v
@@ -10,6 +10,13 @@ import v.pkgconfig
 
 fn (mut c Checker) comptime_call(mut node ast.ComptimeCall) ast.Type {
 	node.left_type = c.expr(node.left)
+	if node.method_name == 'compile_error' {
+		c.error(node.args_var, node.pos)
+		return ast.void_type
+	} else if node.method_name == 'compile_warn' {
+		c.warn(node.args_var, node.pos)
+		return ast.void_type
+	}
 	if node.is_env {
 		env_value := util.resolve_env_value("\$env('$node.args_var')", false) or {
 			c.error(err.msg(), node.env_pos)
diff --git a/vlib/v/checker/tests/compile_error.out b/vlib/v/checker/tests/compile_error.out
new file mode 100644
index 0000000000..c2e7e82c3f
--- /dev/null
+++ b/vlib/v/checker/tests/compile_error.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/compile_error.vv:4:5: error: Only Serenity is supported
+    2 | 
+    3 | $if !serenity {
+    4 |     $compile_error('Only Serenity is supported')
+      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    5 | }
+    6 |
+vlib/v/checker/tests/compile_error.vv:8:5: error: On non Vinix this warning should be shown
+    6 | 
+    7 | $if !vinix {
+    8 |     $compile_warn('On non Vinix this warning should be shown')
+      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    9 | }
+   10 |
diff --git a/vlib/v/checker/tests/compile_error.vv b/vlib/v/checker/tests/compile_error.vv
new file mode 100644
index 0000000000..c0786b6a78
--- /dev/null
+++ b/vlib/v/checker/tests/compile_error.vv
@@ -0,0 +1,15 @@
+module main
+
+$if !serenity {
+    $compile_error('Only Serenity is supported')
+}
+
+$if !vinix {
+    $compile_warn('On non Vinix this warning should be shown')
+}
+
+fn main() {
+	println('Hello from Serenity')
+}
+	
+	
diff --git a/vlib/v/parser/comptime.v b/vlib/v/parser/comptime.v
index 76752823e8..54e1f2a8df 100644
--- a/vlib/v/parser/comptime.v
+++ b/vlib/v/parser/comptime.v
@@ -9,7 +9,8 @@ import v.pref
 import v.token
 
 const (
-	supported_comptime_calls = ['html', 'tmpl', 'env', 'embed_file', 'pkgconfig']
+	supported_comptime_calls = ['html', 'tmpl', 'env', 'embed_file', 'pkgconfig', 'compile_error',
+		'compile_warn']
 	comptime_types           = ['Map', 'Array', 'Int', 'Float', 'Struct', 'Interface', 'Enum',
 		'Sumtype']
 )
@@ -85,9 +86,9 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 	err_node := ast.ComptimeCall{
 		scope: 0
 	}
+	start_pos := p.tok.pos()
 	p.check(.dollar)
-	start_pos := p.prev_tok.pos()
-	error_msg := 'only `\$tmpl()`, `\$env()`, `\$embed_file()`, `\$pkgconfig()` and `\$vweb.html()` comptime functions are supported right now'
+	error_msg := 'only `\$tmpl()`, `\$env()`, `\$embed_file()`, `\$pkgconfig()`, `\$vweb.html()`, `\$compile_error()` and `\$compile_warn()` comptime functions are supported right now'
 	if p.peek_tok.kind == .dot {
 		name := p.check_name() // skip `vweb.html()` TODO
 		if name != 'vweb' {
@@ -96,7 +97,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 		}
 		p.check(.dot)
 	}
-	method_name := p.check_name() // (.name)
+	method_name := p.check_name()
 	if method_name !in parser.supported_comptime_calls {
 		p.error(error_msg)
 		return err_node
@@ -105,8 +106,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 	is_html := method_name == 'html'
 	// $env('ENV_VAR_NAME')
 	p.check(.lpar)
-	spos := p.tok.pos()
-	if method_name == 'env' {
+	if method_name in ['env', 'pkgconfig', 'compile_error', 'compile_warn'] {
 		s := p.tok.lit
 		p.check(.string)
 		p.check(.rpar)
@@ -114,22 +114,10 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 			scope: 0
 			method_name: method_name
 			args_var: s
-			is_env: true
-			env_pos: spos
-			pos: spos.extend(p.prev_tok.pos())
-		}
-	}
-	if method_name == 'pkgconfig' {
-		s := p.tok.lit
-		p.check(.string)
-		p.check(.rpar)
-		return ast.ComptimeCall{
-			scope: 0
-			method_name: method_name
-			args_var: s
-			is_pkgconfig: true
-			env_pos: spos
-			pos: spos.extend(p.prev_tok.pos())
+			is_env: method_name == 'env'
+			is_pkgconfig: method_name == 'pkgconfig'
+			env_pos: start_pos
+			pos: start_pos.extend(p.prev_tok.pos())
 		}
 	}
 	literal_string_param := if is_html { '' } else { p.tok.lit }
@@ -152,7 +140,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 		// Validate that the epath exists, and that it is actually a file.
 		if epath == '' {
 			p.error_with_pos('supply a valid relative or absolute file path to the file to embed',
-				spos)
+				start_pos)
 			return err_node
 		}
 		if !p.pref.is_fmt {
@@ -163,12 +151,12 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 				epath = os.real_path(os.join_path_single(os.dir(p.file_name), epath))
 				if !os.exists(epath) {
 					p.error_with_pos('"$epath" does not exist so it cannot be embedded',
-						spos)
+						start_pos)
 					return err_node
 				}
 				if !os.is_file(epath) {
 					p.error_with_pos('"$epath" is not a file so it cannot be embedded',
-						spos)
+						start_pos)
 					return err_node
 				}
 			} else {