From f7e820cdebf6349e8f6569328affa6beca0513aa Mon Sep 17 00:00:00 2001
From: Turiiya <34311583+ttytm@users.noreply.github.com>
Date: Sun, 19 May 2024 16:57:52 +0200
Subject: [PATCH] v: vet for empty string conditions (#21529)

---
 cmd/tools/modules/vgit/vgit.v                 |  2 +-
 cmd/tools/vdoc/html.v                         |  2 +-
 vlib/v/cflag/cflags.v                         |  2 +-
 vlib/v/checker/checker.v                      |  2 +-
 vlib/v/fmt/fmt.v                              |  2 +-
 vlib/v/gen/c/array.v                          |  4 +--
 vlib/v/gen/c/cgen.v                           | 32 +++++++++----------
 vlib/v/gen/c/match.v                          |  6 ++--
 vlib/v/gen/c/past_tmp_var.v                   |  2 +-
 vlib/v/gen/c/struct.v                         |  2 +-
 vlib/v/gen/golang/golang.v                    |  2 +-
 vlib/v/gen/js/js.v                            |  4 +--
 vlib/v/gen/js/sourcemap/source_map.v          |  8 ++---
 vlib/v/parser/for.v                           |  2 +-
 vlib/v/parser/parser.v                        |  5 +--
 vlib/v/pref/pref.v                            |  2 +-
 vlib/v/tests/bench/bench_strings_similarity.v |  4 +--
 vlib/v/tests/fn_multiple_returns_test.v       |  2 +-
 vlib/v/tests/return_option_call_test.v        |  2 +-
 vlib/v/util/errors.v                          |  2 +-
 vlib/x/json2/decoder2/decode.v                |  2 +-
 vlib/x/json2/encoder.v                        |  2 +-
 22 files changed, 45 insertions(+), 48 deletions(-)

diff --git a/cmd/tools/modules/vgit/vgit.v b/cmd/tools/modules/vgit/vgit.v
index 325254955e232d..30d114a62b066d 100644
--- a/cmd/tools/modules/vgit/vgit.v
+++ b/cmd/tools/modules/vgit/vgit.v
@@ -19,7 +19,7 @@ pub fn check_v_commit_timestamp_before_self_rebuilding(v_timestamp u64) {
 }
 
 pub fn validate_commit_exists(commit string) {
-	if commit.len == 0 {
+	if commit != '' {
 		return
 	}
 	cmd := 'git cat-file -t "${commit}" ' // windows's cmd.exe does not support ' for quoting
diff --git a/cmd/tools/vdoc/html.v b/cmd/tools/vdoc/html.v
index be3584d1e464c1..958948184086e9 100644
--- a/cmd/tools/vdoc/html.v
+++ b/cmd/tools/vdoc/html.v
@@ -536,7 +536,7 @@ fn doc_node_html(dn doc.DocNode, link string, head bool, include_examples bool,
 		} else {
 			dnw.write_string('${tabs(3)}<div class="title"><${head_tag}>${dn.kind} ${sym_name}${hash_link}</${head_tag}>')
 		}
-		if link.len != 0 {
+		if link != '' {
 			dnw.write_string('<a class="link" rel="noreferrer" target="_blank" href="${link}">${link_svg}</a>')
 		}
 		dnw.write_string('</div>\n')
diff --git a/vlib/v/cflag/cflags.v b/vlib/v/cflag/cflags.v
index 3051e30a3f8195..3dff9e72fefa4f 100644
--- a/vlib/v/cflag/cflags.v
+++ b/vlib/v/cflag/cflags.v
@@ -59,7 +59,7 @@ pub fn (cf &CFlag) format() string {
 	} else {
 		value = cf.eval()
 	}
-	if cf.name in ['-l', '-Wa', '-Wl', '-Wp'] && value.len > 0 {
+	if cf.name in ['-l', '-Wa', '-Wl', '-Wp'] && value != '' {
 		return '${cf.name}${value}'.trim_space()
 	}
 	// convert to absolute path
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 6b9fab0c77597b..1877ab8b6d7547 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2018,7 +2018,7 @@ fn (mut c Checker) check_enum_field_integer_literal(expr ast.IntegerLiteral, is_
 
 @[inline]
 fn (mut c Checker) check_loop_label(label string, pos token.Pos) {
-	if label.len == 0 {
+	if label == '' {
 		// ignore
 		return
 	}
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index b40f3cfc1de12e..4a0e8eb098ec6f 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -132,7 +132,7 @@ pub fn (mut f Fmt) write(s string) {
 }
 
 pub fn (mut f Fmt) writeln(s string) {
-	if f.indent > 0 && f.empty_line && s.len > 0 {
+	if f.indent > 0 && f.empty_line && s != '' {
 		f.write_indent()
 	}
 	f.out.writeln(s)
diff --git a/vlib/v/gen/c/array.v b/vlib/v/gen/c/array.v
index 857b73ec34c9b7..79a54b7a3b2af4 100644
--- a/vlib/v/gen/c/array.v
+++ b/vlib/v/gen/c/array.v
@@ -94,7 +94,7 @@ fn (mut g Gen) fixed_array_init(node ast.ArrayInit, array_type Type, var_name st
 
 		ret_typ := g.typ(node.typ)
 		elem_typ := g.typ(node.elem_type)
-		if var_name.len == 0 {
+		if var_name == '' {
 			g.write('${ret_typ} ${past.tmp_var} =')
 		}
 		g.write('{')
@@ -300,7 +300,7 @@ fn (mut g Gen) array_init_with_fields(node ast.ArrayInit, elem_type Type, is_amp
 
 		ret_typ := g.typ(node.typ)
 		elem_typ := g.typ(node.elem_type)
-		if var_name.len == 0 {
+		if var_name == '' {
 			g.write('${ret_typ} ${past.tmp_var} =')
 		}
 		if is_default_array {
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 41f4bf0abf5ff7..1439ffd0a71a22 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -1658,7 +1658,7 @@ pub fn (mut g Gen) write_fn_typesymbol_declaration(sym ast.TypeSymbol) {
 				else {}
 			}
 		}
-		call_conv_attribute_suffix := if call_conv.len != 0 {
+		call_conv_attribute_suffix := if call_conv != '' {
 			'__attribute__((${call_conv}))'
 		} else {
 			''
@@ -5127,24 +5127,24 @@ fn (mut g Gen) hash_stmt(node ast.HashStmt) {
 		}
 		if node.main.contains('.m') {
 			g.definitions.writeln('')
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.definitions.writeln('#if ${ct_condition}')
 			}
 			// Objective C code import, include it after V types, so that e.g. `string` is
 			// available there
 			g.definitions.writeln('// added by module `${node.mod}`, file: ${os.file_name(node.source_file)}:${line_nr}:')
 			g.definitions.writeln(guarded_include)
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.definitions.writeln('#endif // \$if ${ct_condition}')
 			}
 		} else {
 			g.includes.writeln('')
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.includes.writeln('#if ${ct_condition}')
 			}
 			g.includes.writeln('// added by module `${node.mod}`, file: ${os.file_name(node.source_file)}:${line_nr}:')
 			g.includes.writeln(guarded_include)
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.includes.writeln('#endif // \$if ${ct_condition}')
 			}
 		}
@@ -5164,43 +5164,43 @@ fn (mut g Gen) hash_stmt(node ast.HashStmt) {
 			// Might need to support '#preinclude' for .m files as well but for the moment
 			// this does the same as '#include' for them
 			g.definitions.writeln('')
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.definitions.writeln('#if ${ct_condition}')
 			}
 			// Objective C code import, include it after V types, so that e.g. `string` is
 			// available there
 			g.definitions.writeln('// added by module `${node.mod}`, file: ${os.file_name(node.source_file)}:${line_nr}:')
 			g.definitions.writeln(guarded_include)
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.definitions.writeln('#endif // \$if ${ct_condition}')
 			}
 		} else {
 			g.preincludes.writeln('')
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.preincludes.writeln('#if ${ct_condition}')
 			}
 			g.preincludes.writeln('// added by module `${node.mod}`, file: ${os.file_name(node.source_file)}:${line_nr}:')
 			g.preincludes.writeln(guarded_include)
-			if ct_condition.len > 0 {
+			if ct_condition != '' {
 				g.preincludes.writeln('#endif // \$if ${ct_condition}')
 			}
 		}
 	} else if node.kind == 'insert' {
-		if ct_condition.len > 0 {
+		if ct_condition != '' {
 			g.includes.writeln('#if ${ct_condition}')
 		}
 		g.includes.writeln('// inserted by module `${node.mod}`, file: ${os.file_name(node.source_file)}:${line_nr}:')
 		g.includes.writeln(node.val)
-		if ct_condition.len > 0 {
+		if ct_condition != '' {
 			g.includes.writeln('#endif // \$if ${ct_condition}')
 		}
 	} else if node.kind == 'define' {
-		if ct_condition.len > 0 {
+		if ct_condition != '' {
 			g.includes.writeln('#if ${ct_condition}')
 		}
 		g.includes.writeln('// defined by module `${node.mod}`')
 		g.includes.writeln('#define ${node.main}')
-		if ct_condition.len > 0 {
+		if ct_condition != '' {
 			g.includes.writeln('#endif // \$if ${ct_condition}')
 		}
 	}
@@ -5504,7 +5504,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			g.write('return ${tmpvar}')
 		}
 		// Make sure to add our unpacks
-		if multi_unpack.len > 0 {
+		if multi_unpack != '' {
 			g.insert_before_stmt(multi_unpack)
 		}
 		if use_tmp_var && !fn_return_is_option && !fn_return_is_result {
@@ -7219,11 +7219,11 @@ fn (g Gen) get_all_test_function_names() []string {
 		}
 	}
 	mut all_tfuncs := []string{}
-	if tsuite_begin.len > 0 {
+	if tsuite_begin != '' {
 		all_tfuncs << tsuite_begin
 	}
 	all_tfuncs << tfuncs
-	if tsuite_end.len > 0 {
+	if tsuite_end != '' {
 		all_tfuncs << tsuite_end
 	}
 	return all_tfuncs
diff --git a/vlib/v/gen/c/match.v b/vlib/v/gen/c/match.v
index 98883b6c666120..cd393e6f548909 100644
--- a/vlib/v/gen/c/match.v
+++ b/vlib/v/gen/c/match.v
@@ -100,7 +100,7 @@ fn (mut g Gen) match_expr(node ast.MatchExpr) {
 				func_decl = '${def} = &${g.typ(node.return_type)};'
 			}
 		}
-		if func_decl.len > 0 {
+		if func_decl != '' {
 			g.writeln(func_decl) // func, anon func declaration
 		} else {
 			g.writeln('${g.typ(node.return_type)} ${tmp_var} = ${g.type_default(node.return_type)};')
@@ -169,7 +169,7 @@ fn (mut g Gen) match_expr(node ast.MatchExpr) {
 
 fn (mut g Gen) match_expr_sumtype(node ast.MatchExpr, is_expr bool, cond_var string, tmp_var string) {
 	dot_or_ptr := g.dot_or_ptr(node.cond_type)
-	use_ternary := is_expr && tmp_var.len == 0
+	use_ternary := is_expr && tmp_var == ''
 	cond_sym := g.table.sym(node.cond_type)
 	for j, branch in node.branches {
 		mut sumtype_index := 0
@@ -418,7 +418,7 @@ fn (mut g Gen) should_check_low_bound_in_range_expr(expr ast.RangeExpr, node_con
 fn (mut g Gen) match_expr_classic(node ast.MatchExpr, is_expr bool, cond_var string, tmp_var string) {
 	node_cond_type_unsigned := node.cond_type in [ast.u16_type, ast.u32_type, ast.u64_type]
 	type_sym := g.table.final_sym(node.cond_type)
-	use_ternary := is_expr && tmp_var.len == 0
+	use_ternary := is_expr && tmp_var == ''
 	for j, branch in node.branches {
 		is_last := j == node.branches.len - 1
 		if branch.is_else || (use_ternary && is_last) {
diff --git a/vlib/v/gen/c/past_tmp_var.v b/vlib/v/gen/c/past_tmp_var.v
index 3a489d7d9a0037..ead48cff17dca2 100644
--- a/vlib/v/gen/c/past_tmp_var.v
+++ b/vlib/v/gen/c/past_tmp_var.v
@@ -24,7 +24,7 @@ fn (mut g Gen) past_tmp_var_new() PastTmpVar {
 fn (mut g Gen) past_tmp_var_from_var_name(var_name string) PastTmpVar {
 	mut tmp_var := g.new_tmp_var()
 	mut s := ''
-	if var_name.len != 0 {
+	if var_name != '' {
 		tmp_var = var_name
 	} else {
 		s = g.go_before_last_stmt()
diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v
index 312e9e413ed9ca..4f7093dd90c213 100644
--- a/vlib/v/gen/c/struct.v
+++ b/vlib/v/gen/c/struct.v
@@ -627,7 +627,7 @@ fn (mut g Gen) struct_decl(s ast.Struct, name string, is_anon bool) {
 		g.type_definitions.write_string(';')
 	}
 	g.type_definitions.writeln('')
-	if post_pragma.len > 0 {
+	if post_pragma != '' {
 		g.type_definitions.writeln(post_pragma)
 	}
 }
diff --git a/vlib/v/gen/golang/golang.v b/vlib/v/gen/golang/golang.v
index 084656e05b0ace..7a5a6160cba80f 100644
--- a/vlib/v/gen/golang/golang.v
+++ b/vlib/v/gen/golang/golang.v
@@ -92,7 +92,7 @@ pub fn (mut f Gen) write(s string) {
 }
 
 pub fn (mut f Gen) writeln(s string) {
-	if f.indent > 0 && f.empty_line && s.len > 0 {
+	if f.indent > 0 && f.empty_line && s != '' {
 		f.write_indent()
 	}
 	f.out.writeln(s)
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index 00d8e32bf219fd..01da89ef191174 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -393,11 +393,11 @@ fn (g &JsGen) get_all_test_function_names() []string {
 		}
 	}
 	mut all_tfuncs := []string{}
-	if tsuite_begin.len > 0 {
+	if tsuite_begin != '' {
 		all_tfuncs << tsuite_begin
 	}
 	all_tfuncs << tfuncs
-	if tsuite_end.len > 0 {
+	if tsuite_end != '' {
 		all_tfuncs << tsuite_end
 	}
 	return all_tfuncs
diff --git a/vlib/v/gen/js/sourcemap/source_map.v b/vlib/v/gen/js/sourcemap/source_map.v
index b5f465f82c96a2..35f312082e36e5 100644
--- a/vlib/v/gen/js/sourcemap/source_map.v
+++ b/vlib/v/gen/js/sourcemap/source_map.v
@@ -37,13 +37,13 @@ pub fn new_sourcemap(file string, source_root string, sources_content_inline boo
 
 // Add a single mapping from original source line and column to the generated source's line and column for this source map being created.
 pub fn (mut sm SourceMap) add_mapping(source_name string, source_position SourcePositionType, gen_line u32, gen_column u32, name string) {
-	if source_name.len == 0 {
+	if source_name == '' {
 		panic('add_mapping, source_name should not be ""')
 	}
 
 	sources_ind := sm.sources.add(source_name)
 
-	names_ind := if name.len != 0 {
+	names_ind := if name != '' {
 		NameIndexType(IndexNumber(sm.names.add(name)))
 	} else {
 		NameIndexType(Empty{})
@@ -53,14 +53,14 @@ pub fn (mut sm SourceMap) add_mapping(source_name string, source_position Source
 
 // Add multiple mappings from the same source
 pub fn (mut sm SourceMap) add_mapping_list(source_name string, mapping_list []MappingInput) ! {
-	if source_name.len == 0 {
+	if source_name == '' {
 		panic('add_mapping_list, source_name should not be ""')
 	}
 
 	sources_ind := sm.sources.add(source_name)
 
 	for mapping in mapping_list {
-		names_ind := if mapping.name.len != 0 {
+		names_ind := if mapping.name != '' {
 			NameIndexType(IndexNumber(sm.names.add(mapping.name)))
 		} else {
 			NameIndexType(Empty{})
diff --git a/vlib/v/parser/for.v b/vlib/v/parser/for.v
index 860b4e8ab5bb1d..daf7d9228e237c 100644
--- a/vlib/v/parser/for.v
+++ b/vlib/v/parser/for.v
@@ -173,7 +173,7 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 				is_tmp: true
 				is_stack_obj: true
 			})
-			if key_var_name.len > 0 {
+			if key_var_name != '' {
 				return p.error_with_pos('cannot declare index variable with range `for`',
 					key_var_pos)
 			}
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 066db7312a6b67..5128cb4577b28b 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -2712,10 +2712,7 @@ fn (mut p Parser) name_expr() ast.Expr {
 			mod = original_name
 			original_name = p.peek_token(4).lit
 		}
-		mut name := original_name
-		if mod.len > 0 {
-			name = '${mod}.${name}'
-		}
+		name := if mod != '' { '${mod}.${original_name}' } else { original_name }
 		name_w_mod := p.prepend_mod(name)
 		is_c_pointer_cast := language == .c && prev_tok_kind == .amp // `&C.abc(x)` is *always* a cast
 		is_c_type_cast := language == .c && (original_name in ['intptr_t', 'uintptr_t']
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 4207b5afb9e298..9adacb7f169c18 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -286,7 +286,7 @@ fn run_code_in_tmp_vfile_and_exit(args []string, mut res Preferences, option_nam
 	tmp_result := os.system(tmp_cmd)
 	res.vrun_elog('exit code: ${tmp_result}')
 	//
-	if output_option.len != 0 {
+	if output_option != '' {
 		res.vrun_elog('remove tmp exe file: ${tmp_exe_file_path}')
 		os.rm(tmp_exe_file_path) or {}
 	}
diff --git a/vlib/v/tests/bench/bench_strings_similarity.v b/vlib/v/tests/bench/bench_strings_similarity.v
index 13af5eb12b5cbb..8ea1a3d835ab8f 100644
--- a/vlib/v/tests/bench/bench_strings_similarity.v
+++ b/vlib/v/tests/bench/bench_strings_similarity.v
@@ -11,10 +11,10 @@ fn imin(x u16, y u16) u16 {
 // From https://gist.github.com/zeozeozeo/f785910173f3115163bffd0c5240de07
 @[direct_array_access]
 pub fn zeozeozeo_levenshtein_distance(a string, b string) int {
-	if a.len == 0 {
+	if a == '' {
 		return b.len
 	}
-	if b.len == 0 {
+	if b == '' {
 		return a.len
 	}
 	if a == b {
diff --git a/vlib/v/tests/fn_multiple_returns_test.v b/vlib/v/tests/fn_multiple_returns_test.v
index 7f6c4bb3e568bd..224b0b79280881 100644
--- a/vlib/v/tests/fn_multiple_returns_test.v
+++ b/vlib/v/tests/fn_multiple_returns_test.v
@@ -22,7 +22,7 @@ fn fn_mr_get_user() (string, int, []string, UserData) {
 
 fn split_to_two(s string) !(string, string) {
 	mut tokens := s.split_nth(' ', 2)
-	if s.len == 0 {
+	if s == '' {
 		return error('error')
 	}
 	if tokens.len != 2 {
diff --git a/vlib/v/tests/return_option_call_test.v b/vlib/v/tests/return_option_call_test.v
index d4f517cbecb78b..571a41cd672de3 100644
--- a/vlib/v/tests/return_option_call_test.v
+++ b/vlib/v/tests/return_option_call_test.v
@@ -1,5 +1,5 @@
 fn issue(data string) ?(int, string) {
-	if data.len == 0 {
+	if data == '' {
 		return none
 	}
 	return data.len, data
diff --git a/vlib/v/util/errors.v b/vlib/v/util/errors.v
index 3fd3fb1d036f98..54d9d10e747d1e 100644
--- a/vlib/v/util/errors.v
+++ b/vlib/v/util/errors.v
@@ -108,7 +108,7 @@ pub fn path_styled_for_error_messages(path string) string {
 pub fn formatted_error(kind string, omsg string, filepath string, pos token.Pos) string {
 	emsg := omsg.replace('main.', '')
 	path := path_styled_for_error_messages(filepath)
-	position := if filepath.len > 0 {
+	position := if filepath != '' {
 		'${path}:${pos.line_nr + 1}:${mu.max(1, pos.col + 1)}:'
 	} else {
 		''
diff --git a/vlib/x/json2/decoder2/decode.v b/vlib/x/json2/decoder2/decode.v
index 499cfad19d03b1..1797f822a28010 100644
--- a/vlib/x/json2/decoder2/decode.v
+++ b/vlib/x/json2/decoder2/decode.v
@@ -25,7 +25,7 @@ pub enum ValueKind {
 
 // check_json
 fn check_json(val string) ! {
-	if val.len == 0 {
+	if val == '' {
 		return error('empty string')
 	}
 }
diff --git a/vlib/x/json2/encoder.v b/vlib/x/json2/encoder.v
index 3e2f85fa0ed171..8c320cb54aaa67 100644
--- a/vlib/x/json2/encoder.v
+++ b/vlib/x/json2/encoder.v
@@ -448,7 +448,7 @@ pub fn (f Any) prettify_json_str() string {
 // encode_string returns the JSON spec-compliant version of the string.
 @[direct_array_access]
 fn (e &Encoder) encode_string(s string, mut buf []u8) ! {
-	if s.len == 0 {
+	if s == '' {
 		empty := [u8(json2.quote_rune), json2.quote_rune]!
 		unsafe { buf.push_many(&empty[0], 2) }
 		return