From 6751be9645d8d4ae1826704c1f74156acc2b2424 Mon Sep 17 00:00:00 2001
From: Delius <bontequero@gmail.com>
Date: Mon, 21 Jan 2019 12:29:36 +0300
Subject: [PATCH] checkers: add hexLiterals (#772)

---
 checkers/hexLiterals_checker.go               | 94 +++++++++++++++++++
 .../testdata/hexLiterals/negative_tests.go    |  7 ++
 .../testdata/hexLiterals/positive_tests.go    | 15 +++
 3 files changed, 116 insertions(+)
 create mode 100644 checkers/hexLiterals_checker.go
 create mode 100644 checkers/testdata/hexLiterals/negative_tests.go
 create mode 100644 checkers/testdata/hexLiterals/positive_tests.go

diff --git a/checkers/hexLiterals_checker.go b/checkers/hexLiterals_checker.go
new file mode 100644
index 000000000..6f24b2980
--- /dev/null
+++ b/checkers/hexLiterals_checker.go
@@ -0,0 +1,94 @@
+package checkers
+
+import (
+	"go/ast"
+	"strings"
+	"unicode"
+
+	"github.com/go-lintpack/lintpack"
+	"github.com/go-lintpack/lintpack/astwalk"
+	"github.com/go-toolsmith/astcast"
+	"github.com/go-toolsmith/astp"
+)
+
+func init() {
+	var info lintpack.CheckerInfo
+	info.Name = "hexLiterals"
+	info.Tags = []string{"style", "experimental"}
+	info.Summary = ""
+	info.Before = `
+x := 0X12
+y := 0xfF`
+	info.After = `
+x := 0x12
+// (A)
+y := 0xff
+// (B)
+y := 0xFF`
+
+	collection.AddChecker(&info, func(ctx *lintpack.CheckerContext) lintpack.FileWalker {
+		return astwalk.WalkerForExpr(&hexLiteralChecker{ctx: ctx})
+	})
+}
+
+type hexLiteralChecker struct {
+	astwalk.WalkHandler
+	ctx *lintpack.CheckerContext
+}
+
+func (c *hexLiteralChecker) VisitExpr(expr ast.Expr) {
+	if !astp.IsBasicLit(expr) {
+		return
+	}
+	v := astcast.ToBasicLit(expr)
+
+	if !strings.HasPrefix(v.Value, "0X") && !strings.HasPrefix(v.Value, "0x") {
+		return
+	}
+
+	prefix := v.Value[:2]
+	value := v.Value[2:]
+
+	switch prefix {
+	case "0X":
+		if isAnyLetter(value) {
+			if isGoodHex(value) {
+				c.ctx.Warn(expr, "Should be 0x%s", value)
+				return
+			}
+			c.ctx.Warn(expr,
+				"Should be 0x%s or 0x%s",
+				strings.ToLower(value),
+				strings.ToUpper(value))
+			return
+		}
+
+		c.ctx.Warn(expr, "Should be 0x%s", value)
+	case "0x":
+		if isAnyLetter(value) {
+			if isGoodHex(value) {
+				return
+			}
+			c.ctx.Warn(expr,
+				"Should be 0x%s or 0x%s",
+				strings.ToLower(value),
+				strings.ToUpper(value))
+			return
+		}
+
+		c.ctx.Warn(expr, "Should be 0x%s", value)
+	}
+}
+
+func isAnyLetter(s string) bool {
+	for _, r := range s {
+		if unicode.IsLetter(r) {
+			return true
+		}
+	}
+	return false
+}
+
+func isGoodHex(value string) bool {
+	return value == strings.ToLower(value) || value == strings.ToUpper(value)
+}
diff --git a/checkers/testdata/hexLiterals/negative_tests.go b/checkers/testdata/hexLiterals/negative_tests.go
new file mode 100644
index 000000000..4ebac8dff
--- /dev/null
+++ b/checkers/testdata/hexLiterals/negative_tests.go
@@ -0,0 +1,7 @@
+package checker_test
+
+func negatives() {
+	_ = 0xFF
+	_ = 0xff
+	_ = "0xfF"
+}
diff --git a/checkers/testdata/hexLiterals/positive_tests.go b/checkers/testdata/hexLiterals/positive_tests.go
new file mode 100644
index 000000000..407a919ed
--- /dev/null
+++ b/checkers/testdata/hexLiterals/positive_tests.go
@@ -0,0 +1,15 @@
+package checker_test
+
+func someTest() {
+	/*! Should be 0x12 */
+	_ = 0X12
+
+	/*! Should be 0xff or 0xFF */
+	_ = 0xfF
+
+	/*! Should be 0xEE */
+	_ = 0XEE
+
+	/*! Should be 0xaa */
+	_ = 0Xaa
+}