From c6a829ce8287ab85e70f3ea45dc885acd3c18082 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Fri, 24 Apr 2020 18:35:33 +0300
Subject: [PATCH] cgen: support for error('abc').str() and printing errors

---
 vlib/builtin/option.v                   | 11 ++++++++++-
 vlib/v/gen/cgen.v                       | 11 +++++++++++
 vlib/v/tests/option_print_errors_test.v | 21 +++++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/option_print_errors_test.v

diff --git a/vlib/builtin/option.v b/vlib/builtin/option.v
index 133c8d9e23..a0c64d87e7 100644
--- a/vlib/builtin/option.v
+++ b/vlib/builtin/option.v
@@ -21,6 +21,16 @@ struct Option {
 	is_none bool
 }
 
+pub fn (o Option) str() string {
+   if o.ok && !o.is_none {
+	  return 'Option{ data: ' + o.data[0..32].hex() + ' }'
+   }
+   if o.is_none {
+	  return 'Option{ none }'	  
+   }
+   return 'Option{ error: "${o.error}" }'
+}
+
 // `fn foo() ?Foo { return foo }` => `fn foo() ?Foo { return opt_ok(foo); }`
 fn opt_ok(data voidptr, size int) Option {
 	if size >= 400 {
@@ -52,4 +62,3 @@ pub fn error_with_code(s string, code int) Option {
 		ecode: code
 	}
 }
-
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index a323f8bf1c..e21169a080 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -2315,6 +2315,8 @@ fn (mut g Gen) string_inter_literal(node ast.StringInterLiteral) {
 			g.write('%"PRId64"')
 		} else if node.expr_types[i] == table.u64_type {
 			g.write('%"PRIu64"')
+		} else if g.typ( node.expr_types[i] ).starts_with('Option') {
+			g.write('%.*s')
 		} else {
 			g.write('%"PRId32"')
 		}
@@ -2405,6 +2407,15 @@ fn (mut g Gen) string_inter_literal(node ast.StringInterLiteral) {
 				g.write('${str_fn_name}(')
 				g.expr(expr)
 				g.write(',0).str')
+			} else if g.typ(  node.expr_types[i] ).starts_with('Option') {
+				str_fn_name := 'Option_str'
+				g.write('${str_fn_name}((Option)')
+				g.expr(expr)
+				g.write(')')
+				g.write('.len, ')
+				g.write('${str_fn_name}((Option)')
+				g.expr(expr)
+				g.write(').str')
 			} else {
 				g.expr(expr)
 			}
diff --git a/vlib/v/tests/option_print_errors_test.v b/vlib/v/tests/option_print_errors_test.v
new file mode 100644
index 0000000000..3992c0a75a
--- /dev/null
+++ b/vlib/v/tests/option_print_errors_test.v
@@ -0,0 +1,21 @@
+
+fn test_error_can_be_converted_to_string(){
+	assert 'Option{ error: "an error" }' == error('an error').str()
+}
+
+fn test_error_can_be_assigned_to_a_variable(){
+	f := error('an error')
+	assert 'Option{ error: "an error" }' == f.str()
+}
+
+fn test_error_can_be_printed(){
+	f := error('an error')
+	println(f)
+	assert true
+}
+
+fn test_error_can_be_interpolated_in_a_string(){
+	f := error('an error')
+	s := 'hi $f'
+	assert s == 'hi Option{ error: "an error" }'
+}