feat: implement -key-naming-case

README.md

@@ -11,7 +11,7 @@ A Go linter that ensures consistent code style when using `log/slog`.
 
 The `log/slog` API allows two different types of arguments: key-value pairs and attributes.
 People may have different opinions about which one is better,
-but nobody probably wants to mix them up because it makes the code harder to read.
+but nobody probably wants to mix them up because it makes the code harder to read:
 
 ```go
 slog.Info("a user has logged in", "user_id", 42, slog.String("ip_address", "192.0.2.0")) // ugh
@@ -26,6 +26,7 @@ The linter has several options, so you can adjust it to your own code style.
 * Enforce using either key-value pairs or attributes for the entire project (optional)
 * Enforce using methods that accept a context (optional)
 * Enforce using constants instead of raw keys (optional)
+* Enforce a single key naming convention (optional)
 * Enforce putting arguments on separate lines (optional)
 
 ## 📦 Install
@@ -40,15 +41,15 @@ sloglint [flags] ./...
 
 ### Key-value pairs only
 
-The `-kv-only` flag causes `sloglint` to report any use of attributes.
+The `-kv-only` flag causes `sloglint` to report any use of attributes:
 
 ```go
 slog.Info("a user has logged in", slog.Int("user_id", 42)) // sloglint: attributes should not be used
 ```
 
 ### Attributes only
 
-In contrast, the `-attr-only` flag causes `sloglint` to report any use of key-value pairs.
+In contrast, the `-attr-only` flag causes `sloglint` to report any use of key-value pairs:
 
 ```go
 slog.Info("a user has logged in", "user_id", 42) // sloglint: key-value pairs should not be used
@@ -58,13 +59,13 @@ slog.Info("a user has logged in", "user_id", 42) // sloglint: key-value pairs sh
 
 Some `slog.Handler` implementations make use of the given `context.Context` (e.g. to access context values).
 For them to work properly, you need to pass a context to all logger calls.
-The `-context-only` flag causes `sloglint` to report the use of methods without a context.
+The `-context-only` flag causes `sloglint` to report the use of methods without a context:
 
 ```go
 slog.Info("a user has logged in") // sloglint: methods without a context should not be used
 ```
 
-This report can be fixed by using the equivalent method with the `Context` suffix.
+This report can be fixed by using the equivalent method with the `Context` suffix:
 
 ```go
 slog.InfoContext(ctx, "a user has logged in")
@@ -73,7 +74,8 @@ slog.InfoContext(ctx, "a user has logged in")
 ### No raw keys
 
 To prevent typos, you may want to forbid the use of raw keys altogether.
-The `-no-raw-keys` flag causes `sloglint` to report the use of strings as keys (including `slog.Attr` calls, e.g. `slog.Int("user_id", 42)`).
+The `-no-raw-keys` flag causes `sloglint` to report the use of strings as keys
+(including `slog.Attr` calls, e.g. `slog.Int("user_id", 42)`):
 
 ```go
 slog.Info("a user has logged in", "user_id", 42) // sloglint: raw keys should not be used
@@ -87,7 +89,7 @@ const UserId = "user_id"
 slog.Info("a user has logged in", UserId, 42)
 ```
 
-...or custom `slog.Attr` constructors.
+...or custom `slog.Attr` constructors:
 
 ```go
 func UserId(value int) slog.Attr { return slog.Int("user_id", value) }
@@ -97,16 +99,25 @@ slog.Info("a user has logged in", UserId(42))
 
 > 💡 Such helpers can be automatically generated for you by the [`sloggen`][2] tool. Give it a try too!
 
+### Key naming convention
+
+To ensure consistency in logs, you may want to enforce a single key naming convention.
+The `-key-naming-case=<snake|kebab|camel|pascal>` flag causes `sloglint` to report keys written in a case other than the given one:
+
+```go
+slog.Info("a user has logged in", "user-id", 42) // sloglint: keys should be written in snake_case
+```
+
 ### Arguments on separate lines
 
 To improve code readability, you may want to put arguments on separate lines, especially when using key-value pairs.
-The `-args-on-sep-lines` flag causes `sloglint` to report 2+ arguments on the same line.
+The `-args-on-sep-lines` flag causes `sloglint` to report 2+ arguments on the same line:
 
 ```go
 slog.Info("a user has logged in", "user_id", 42, "ip_address", "192.0.2.0") // sloglint: arguments should be put on separate lines
 ```
 
-This report can be fixed by reformatting the code.
+This report can be fixed by reformatting the code:
 
 ```go
 slog.Info("a user has logged in",

go.mod

@@ -2,7 +2,10 @@ module go-simpler.org/sloglint
 
 go 1.20
 
-require golang.org/x/tools v0.14.0
+require (
+	github.com/ettle/strcase v0.1.1
+	golang.org/x/tools v0.14.0
+)
 
 require (
 	golang.org/x/mod v0.13.0 // indirect

go.sum

@@ -1,7 +1,19 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/ettle/strcase v0.1.1 h1:htFueZyVeE1XNnMEfbqp5r67qAN/4r6ya1ysq8Q+Zcw=
+github.com/ettle/strcase v0.1.1/go.mod h1:hzDLsPC7/lwKyBOywSHEP89nt2pDgdy+No1NBA9o9VY=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
+github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 golang.org/x/mod v0.13.0 h1:I/DsJXRlw/8l/0c24sM9yb0T4z9liZTduXvdAWYiysY=
 golang.org/x/mod v0.13.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.4.0 h1:zxkM55ReGkDlKSM+Fu41A+zmbZuaPVbGMzvvdUPznYQ=
 golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/tools v0.14.0 h1:jvNa2pY0M4r62jkRQ6RwEZZyPcymeL9XZMLBbV7U2nc=
 golang.org/x/tools v0.14.0/go.mod h1:uYBEerGOWcJyEORxN+Ek8+TT266gXkNlHdJBwexUsBg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

sloglint.go

@@ -4,11 +4,13 @@
 import (
 	"errors"
 	"flag"
+	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
 	"strconv"
 
+	"github.com/ettle/strcase"
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/inspect"
 	"golang.org/x/tools/go/ast/inspector"
@@ -17,11 +19,12 @@
 
 // Options are options for the sloglint analyzer.
 type Options struct {
-	KVOnly         bool // Enforce using key-value pairs only (incompatible with AttrOnly).
-	AttrOnly       bool // Enforce using attributes only (incompatible with KVOnly).
-	ContextOnly    bool // Enforce using methods that accept a context.
-	NoRawKeys      bool // Enforce using constants instead of raw keys.
-	ArgsOnSepLines bool // Enforce putting arguments on separate lines.
+	KVOnly         bool   // Enforce using key-value pairs only (incompatible with AttrOnly).
+	AttrOnly       bool   // Enforce using attributes only (incompatible with KVOnly).
+	ContextOnly    bool   // Enforce using methods that accept a context.
+	NoRawKeys      bool   // Enforce using constants instead of raw keys.
+	KeyNamingCase  string // Enforce a single key naming convention ("snake", "kebab", "camel", or "pascal").
+	ArgsOnSepLines bool   // Enforce putting arguments on separate lines.
 }
 
 // New creates a new sloglint analyzer.
@@ -44,6 +47,13 @@
 	}
 }
 
+const (
+	snakeCase  = "snake"
+	kebabCase  = "kebab"
+	camelCase  = "camel"
+	pascalCase = "pascal"
+)
+
 func flags(opts *Options) flag.FlagSet {
 	fs := flag.NewFlagSet("sloglint", flag.ContinueOnError)
 
@@ -61,6 +71,16 @@
 	boolVar(&opts.NoRawKeys, "no-raw-keys", "enforce using constants instead of raw keys")
 	boolVar(&opts.ArgsOnSepLines, "args-on-sep-lines", "enforce putting arguments on separate lines")
 
+	fs.Func("key-naming-case", "enforce a single key naming convention (snake|kebab|camel|pascal)", func(s string) error {
+		switch s {
+		case snakeCase, kebabCase, camelCase, pascalCase:
+			opts.KeyNamingCase = s
+			return nil
+		default:
+			return fmt.Errorf("sloglint: -key-naming-case=%s: invalid value", s)
+		}
+	})
+
 	return *fs
 }
 
@@ -160,6 +180,17 @@
 		if opts.ArgsOnSepLines && argsOnSameLine(pass.Fset, call, keys, attrs) {
 			pass.Reportf(call.Pos(), "arguments should be put on separate lines")
 		}
+
+		switch {
+		case opts.KeyNamingCase == snakeCase && badKeyNames(pass.TypesInfo, strcase.ToSnake, keys, attrs):
+			pass.Reportf(call.Pos(), "keys should be written in snake_case")
+		case opts.KeyNamingCase == kebabCase && badKeyNames(pass.TypesInfo, strcase.ToKebab, keys, attrs):
+			pass.Reportf(call.Pos(), "keys should be written in kebab-case")
+		case opts.KeyNamingCase == camelCase && badKeyNames(pass.TypesInfo, strcase.ToCamel, keys, attrs):
+			pass.Reportf(call.Pos(), "keys should be written in camelCase")
+		case opts.KeyNamingCase == pascalCase && badKeyNames(pass.TypesInfo, strcase.ToPascal, keys, attrs):
+			pass.Reportf(call.Pos(), "keys should be written in PascalCase")
+		}
 	})
 }
 
@@ -211,6 +242,64 @@
 	return false
 }
 
+func badKeyNames(info *types.Info, caseFn func(string) string, keys, attrs []ast.Expr) bool {
+	for _, key := range keys {
+		if name, ok := getKeyName(key); ok && name != caseFn(name) {
+			return true
+		}
+	}
+
+	for _, attr := range attrs {
+		var expr ast.Expr
+		switch attr := attr.(type) {
+		case *ast.CallExpr: // e.g. slog.Int()
+			fn := typeutil.StaticCallee(info, attr)
+			if _, ok := attrFuncs[fn.FullName()]; ok {
+				expr = attr.Args[0]
+			}
+		case *ast.CompositeLit: // slog.Attr{}
+			switch len(attr.Elts) {
+			case 1: // slog.Attr{Key: ...} | slog.Attr{Value: ...}
+				if kv := attr.Elts[0].(*ast.KeyValueExpr); kv.Key.(*ast.Ident).Name == "Key" {
+					expr = kv.Value
+				}
+			case 2: // slog.Attr{..., ...} | slog.Attr{Key: ..., Value: ...}
+				expr = attr.Elts[0]
+				if kv1, ok := attr.Elts[0].(*ast.KeyValueExpr); ok && kv1.Key.(*ast.Ident).Name == "Key" {
+					expr = kv1.Value
+				}
+				if kv2, ok := attr.Elts[1].(*ast.KeyValueExpr); ok && kv2.Key.(*ast.Ident).Name == "Key" {
+					expr = kv2.Value
+				}
+			}
+		}
+		if name, ok := getKeyName(expr); ok && name != caseFn(name) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func getKeyName(expr ast.Expr) (string, bool) {
+	if expr == nil {
+		return "", false
+	}
+	if ident, ok := expr.(*ast.Ident); ok {
+		if ident.Obj == nil || ident.Obj.Decl == nil || ident.Obj.Kind != ast.Con {
+			return "", false
+		}
+		if spec, ok := ident.Obj.Decl.(*ast.ValueSpec); ok && len(spec.Values) > 0 {
+			// TODO: support len(spec.Values) > 1; e.g. "const foo, bar = 1, 2"
+			expr = spec.Values[0]
+		}
+	}
+	if lit, ok := expr.(*ast.BasicLit); ok && lit.Kind == token.STRING {
+		return lit.Value, true
+	}
+	return "", false
+}
+
 func argsOnSameLine(fset *token.FileSet, call ast.Expr, keys, attrs []ast.Expr) bool {
 	if len(keys)+len(attrs) <= 1 {
 		return false // special case: slog.Info("msg", "key", "value") is ok.

sloglint_test.go

@@ -35,6 +35,11 @@ func TestAnalyzer(t *testing.T) {
 		analysistest.Run(t, testdata, analyzer, "no_raw_keys")
 	})
 
+	t.Run("key naming case", func(t *testing.T) {
+		analyzer := sloglint.New(&sloglint.Options{KeyNamingCase: "snake"})
+		analysistest.Run(t, testdata, analyzer, "key_naming_case")
+	})
+
 	t.Run("arguments on separate lines", func(t *testing.T) {
 		analyzer := sloglint.New(&sloglint.Options{ArgsOnSepLines: true})
 		analysistest.Run(t, testdata, analyzer, "args_on_sep_lines")

testdata/src/key_naming_case/key_naming_case.go

@@ -0,0 +1,38 @@
+package key_naming_case
+
+import "log/slog"
+
+const (
+	snakeKey = "foo_bar"
+	kebabKey = "foo-bar"
+)
+
+func tests() {
+	slog.Info("msg")
+	slog.Info("msg", "foo_bar", 1)
+	slog.Info("msg", snakeKey, 1)
+	slog.Info("msg", slog.Int("foo_bar", 1))
+	slog.Info("msg", slog.Int(snakeKey, 1))
+	slog.Info("msg", slog.Attr{})
+	slog.Info("msg", slog.Attr{"foo_bar", slog.IntValue(1)})
+	slog.Info("msg", slog.Attr{snakeKey, slog.IntValue(1)})
+	slog.Info("msg", slog.Attr{Key: "foo_bar"})
+	slog.Info("msg", slog.Attr{Key: snakeKey})
+	slog.Info("msg", slog.Attr{Key: "foo_bar", Value: slog.IntValue(1)})
+	slog.Info("msg", slog.Attr{Key: snakeKey, Value: slog.IntValue(1)})
+	slog.Info("msg", slog.Attr{Value: slog.IntValue(1), Key: "foo_bar"})
+	slog.Info("msg", slog.Attr{Value: slog.IntValue(1), Key: snakeKey})
+
+	slog.Info("msg", "foo-bar", 1)                                       // want `keys should be written in snake_case`
+	slog.Info("msg", kebabKey, 1)                                        // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Int("foo-bar", 1))                             // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Int(kebabKey, 1))                              // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{"foo-bar", slog.IntValue(1)})             // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{kebabKey, slog.IntValue(1)})              // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{Key: "foo-bar"})                          // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{Key: kebabKey})                           // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{Key: "foo-bar", Value: slog.IntValue(1)}) // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{Key: kebabKey, Value: slog.IntValue(1)})  // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{Value: slog.IntValue(1), Key: "foo-bar"}) // want `keys should be written in snake_case`
+	slog.Info("msg", slog.Attr{Value: slog.IntValue(1), Key: kebabKey})  // want `keys should be written in snake_case`
+}

testdata/src/mixed_args/mixed_args.go

@@ -6,15 +6,14 @@ import (
 )
 
 func tests() {
+	logger := slog.New(nil)
+	ctx := context.Background()
+
 	slog.Info("msg")
 	slog.Info("msg", "foo", 1)
 	slog.Info("msg", "foo", 1, "bar", 2)
 	slog.Info("msg", slog.Int("foo", 1))
 	slog.Info("msg", slog.Int("foo", 1), slog.Int("bar", 2))
-}
-
-func allFuncs() {
-	ctx := context.Background()
 
 	slog.Log(ctx, slog.LevelInfo, "msg", "foo", 1, slog.Int("bar", 2)) // want `key-value pairs and attributes should not be mixed`
 	slog.Debug("msg", "foo", 1, slog.Int("bar", 2))                    // want `key-value pairs and attributes should not be mixed`
@@ -26,7 +25,6 @@ func allFuncs() {
 	slog.WarnContext(ctx, "msg", "foo", 1, slog.Int("bar", 2))         // want `key-value pairs and attributes should not be mixed`
 	slog.ErrorContext(ctx, "msg", "foo", 1, slog.Int("bar", 2))        // want `key-value pairs and attributes should not be mixed`
 
-	logger := slog.New(nil)
 	logger.Log(ctx, slog.LevelInfo, "msg", "foo", 1, slog.Int("bar", 2)) // want `key-value pairs and attributes should not be mixed`
 	logger.Debug("msg", "foo", 1, slog.Int("bar", 2))                    // want `key-value pairs and attributes should not be mixed`
 	logger.Info("msg", "foo", 1, slog.Int("bar", 2))                     // want `key-value pairs and attributes should not be mixed`

testdata/src/no_raw_keys/no_raw_keys.go

@@ -18,10 +18,12 @@ func tests() {
 	slog.Info("msg", slog.Attr{Key: foo})
 	slog.Info("msg", slog.Attr{Value: slog.IntValue(1)})
 	slog.Info("msg", slog.Attr{Key: foo, Value: slog.IntValue(1)})
+	slog.Info("msg", slog.Attr{Value: slog.IntValue(1), Key: foo})
 
 	slog.Info("msg", "foo", 1)                                       // want `raw keys should not be used`
 	slog.Info("msg", slog.Int("foo", 1))                             // want `raw keys should not be used`
 	slog.Info("msg", slog.Attr{"foo", slog.IntValue(1)})             // want `raw keys should not be used`
 	slog.Info("msg", slog.Attr{Key: "foo"})                          // want `raw keys should not be used`
 	slog.Info("msg", slog.Attr{Key: "foo", Value: slog.IntValue(1)}) // want `raw keys should not be used`
+	slog.Info("msg", slog.Attr{Value: slog.IntValue(1), Key: "foo"}) // want `raw keys should not be used`
 }