From 12c7816c5844852e71628b0360ffec8d6d731545 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 25 Mar 2026 16:42:22 +0300
Subject: [PATCH] cgen: improve error message when running shader examples
 (fixes #16125)

---
 .../07_simple_shader_glsl/simple_shader.v     |  2 +-
 .../tests/missing_shader_header_1.glsl        |  1 +
 .../checker/tests/missing_shader_header_1.out |  1 +
 .../checker/tests/missing_shader_header_1.vv  |  3 ++
 vlib/v/gen/c/cgen.v                           | 36 ++++++++++++++++---
 5 files changed, 37 insertions(+), 6 deletions(-)
 create mode 100644 vlib/v/checker/tests/missing_shader_header_1.glsl
 create mode 100644 vlib/v/checker/tests/missing_shader_header_1.out
 create mode 100644 vlib/v/checker/tests/missing_shader_header_1.vv

diff --git a/examples/sokol/07_simple_shader_glsl/simple_shader.v b/examples/sokol/07_simple_shader_glsl/simple_shader.v
index db1d07bb5..d6d5606d6 100644
--- a/examples/sokol/07_simple_shader_glsl/simple_shader.v
+++ b/examples/sokol/07_simple_shader_glsl/simple_shader.v
@@ -10,7 +10,7 @@ import sokol.gfx
 // Use `v shader` or `sokol-shdc` to generate the necessary `.h` file
 // Using `v shader -v .` in this directory will show some additional
 // info - and what you should include to make things work.
-#include "@VMODROOT/simple_shader.h" # # It should be generated with `v shader .`
+#include "@VMODROOT/simple_shader.h" # It should be generated with `v shader .`
 
 // simple_shader_desc is a C function declaration defined by
 // the `@program` entry in the `simple_shader.glsl` shader file.
diff --git a/vlib/v/checker/tests/missing_shader_header_1.glsl b/vlib/v/checker/tests/missing_shader_header_1.glsl
new file mode 100644
index 000000000..2dad8e152
--- /dev/null
+++ b/vlib/v/checker/tests/missing_shader_header_1.glsl
@@ -0,0 +1 @@
+// A matching .glsl file lets the compiler suggest `v shader`.
diff --git a/vlib/v/checker/tests/missing_shader_header_1.out b/vlib/v/checker/tests/missing_shader_header_1.out
new file mode 100644
index 000000000..bdb3f62d8
--- /dev/null
+++ b/vlib/v/checker/tests/missing_shader_header_1.out
@@ -0,0 +1 @@
+builder error: Header file "missing_shader_header_1.h", needed for module `main` was not found. This header can be generated from `missing_shader_header_1.glsl`. Run `v shader .` in that directory to create it.
diff --git a/vlib/v/checker/tests/missing_shader_header_1.vv b/vlib/v/checker/tests/missing_shader_header_1.vv
new file mode 100644
index 000000000..5814319d9
--- /dev/null
+++ b/vlib/v/checker/tests/missing_shader_header_1.vv
@@ -0,0 +1,3 @@
+module main
+
+#include "missing_shader_header_1.h"
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index a6862b922..939720ea8 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -7701,13 +7701,39 @@ fn (g &Gen) is_error_type(typ ast.Type) bool {
 	return false
 }
 
-fn (mut g Gen) hash_stmt_guarded_include(node ast.HashStmt) string {
-	mut missing_message := 'Header file ${node.main}, needed for module `${node.mod}` was not found.'
+fn missing_shader_header_message(node ast.HashStmt) string {
 	if node.msg != '' {
-		missing_message += ' ${node.msg}.'
-	} else {
-		missing_message += ' Please install the corresponding development headers.'
+		return '${node.msg}.'
+	}
+	if shader_source := matching_generated_shader_source(node) {
+		shader_name := os.file_name(shader_source)
+		return 'This header can be generated from `${shader_name}`. Run `v shader .` in that directory to create it.'
+	}
+	return 'Please install the corresponding development headers.'
+}
+
+fn matching_generated_shader_source(node ast.HashStmt) ?string {
+	if node.main.starts_with('<') && node.main.ends_with('>') {
+		return none
 	}
+	header_path := node.main.trim('"')
+	if os.file_ext(header_path) != '.h' {
+		return none
+	}
+	mut resolved_header_path := header_path
+	if !os.is_abs_path(resolved_header_path) {
+		resolved_header_path = os.join_path(os.dir(node.source_file), resolved_header_path)
+	}
+	shader_source := resolved_header_path.all_before_last('.') + '.glsl'
+	if !os.is_file(shader_source) {
+		return none
+	}
+	return shader_source
+}
+
+fn (mut g Gen) hash_stmt_guarded_include(node ast.HashStmt) string {
+	mut missing_message := 'Header file ${node.main}, needed for module `${node.mod}` was not found.'
+	missing_message += ' ${missing_shader_header_message(node)}'
 	mut guarded_include := get_guarded_include_text(node.main, missing_message)
 	if node.main == '<errno.h>' {
 		// fails with musl-gcc and msvc; but an unguarded include works:
-- 
2.39.5