Add support for finding constants with duplicated values. (#30)

* feat: add find-duplicates flag

* fix: update readme

Author: kalexmills

README.md

@@ -28,6 +28,7 @@ Flags:
   -min-occurrences   report from how many occurrences (default: 2)
   -min-length        only report strings with the minimum given length (default: 3)
   -match-constant    look for existing constants matching the values
+  -find-duplicates   look for constants with identical values
   -numbers           search also for duplicated numbers
   -min          	   minimum value, only works with -numbers
   -max          	   maximum value, only works with -numbers

api.go

@@ -3,18 +3,21 @@ package goconst
 import (
 	"go/ast"
 	"go/token"
+	"sort"
 	"strings"
 	"sync"
 )
 
-// Issue represents a finding of duplicated strings or numbers.
+// Issue represents a finding of duplicated strings, numbers, or constants.
 // Each Issue includes the position where it was found, how many times it occurs,
 // the string itself, and any matching constant name.
 type Issue struct {
 	Pos              token.Position
 	OccurrencesCount int
 	Str              string
 	MatchingConst    string
+	DuplicateConst   string
+	DuplicatePos     token.Position
 }
 
 // IssuePool provides a pool of Issue slices to reduce allocations
@@ -61,6 +64,8 @@ type Config struct {
 	NumberMax int
 	// ExcludeTypes allows excluding specific types of contexts
 	ExcludeTypes map[Type]bool
+	// FindDuplicated constants enables finding constants whose values match existing constants in other packages.
+	FindDuplicates bool
 }
 
 // Run analyzes the provided AST files for duplicated strings or numbers
@@ -74,6 +79,7 @@ func Run(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue, error) {
 		cfg.IgnoreTests,
 		cfg.MatchWithConstants,
 		cfg.ParseNumbers,
+		cfg.FindDuplicates,
 		cfg.NumberMin,
 		cfg.NumberMax,
 		cfg.MinStringLength,
@@ -155,6 +161,8 @@ func Run(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue, error) {
 		}
 	}
 
+	sort.Strings(stringKeys)
+
 	// Process strings in a predictable order for stable output
 	for _, str := range stringKeys {
 		positions := p.strs[str]
@@ -175,9 +183,9 @@ func Run(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue, error) {
 		// Check for matching constants
 		if len(p.consts) > 0 {
 			p.constMutex.RLock()
-			if cst, ok := p.consts[str]; ok {
+			if csts, ok := p.consts[str]; ok && len(csts) > 0 {
 				// const should be in the same package and exported
-				issue.MatchingConst = cst.Name
+				issue.MatchingConst = csts[0].Name
 			}
 			p.constMutex.RUnlock()
 		}
@@ -188,6 +196,37 @@ func Run(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue, error) {
 	p.stringCountMutex.RUnlock()
 	p.stringMutex.RUnlock()
 
+	// process duplicate constants
+	p.constMutex.RLock()
+
+	// reuse string buffer for const keys
+	stringKeys = stringKeys[:0]
+
+	// Create an array of strings and sort for stable output
+	for str := range p.consts {
+		if len(p.consts[str]) > 1 {
+			stringKeys = append(stringKeys, str)
+		}
+	}
+
+	sort.Strings(stringKeys)
+
+	// report an issue for every duplicated const
+	for _, str := range stringKeys {
+		positions := p.consts[str]
+
+		for i := 1; i < len(positions); i++ {
+			issueBuffer = append(issueBuffer, Issue{
+				Pos:            positions[i].Position,
+				Str:            str,
+				DuplicateConst: positions[0].Name,
+				DuplicatePos:   positions[0].Position,
+			})
+		}
+	}
+
+	p.constMutex.RUnlock()
+
 	// Return string buffer to pool
 	PutStringBuffer(stringKeys)
 

api_test.go

@@ -41,6 +41,18 @@ func example() {
 			},
 			expectedIssues: 1,
 		},
+		{
+			name: "duplicate consts",
+			code: `package example
+const ConstA = "test"
+func example() {
+	const ConstB = "test"
+}`,
+			config: &Config{
+				FindDuplicates: true,
+			},
+			expectedIssues: 1,
+		},
 		{
 			name: "string duplication with ignore",
 			code: `package example
@@ -212,50 +224,93 @@ func example() {
 
 func TestMultipleFilesAnalysis(t *testing.T) {
 	// Test analyzing multiple files at once
-	code1 := `package example
+	tests := []struct {
+		name                    string
+		code1                   string
+		code2                   string
+		config                  *Config
+		expectedIssues          int
+		expectedStr             string
+		expectedOccurrenceCount int
+	}{
+		{
+			name: "duplicate strings",
+			code1: `package example
 func example1() {
 	a := "shared"
 	b := "shared"
 }
-`
-	code2 := `package example
+`,
+			code2: `package example
 func example2() {
 	c := "shared"
 	d := "unique"
 }
-`
-	fset := token.NewFileSet()
-	f1, err := parser.ParseFile(fset, "file1.go", code1, 0)
-	if err != nil {
-		t.Fatalf("Failed to parse test code: %v", err)
+`,
+			config: &Config{
+				MinStringLength: 3,
+				MinOccurrences:  2,
+			},
+			expectedIssues:          1,
+			expectedStr:             "shared",
+			expectedOccurrenceCount: 3,
+		},
+		{
+			name: "duplicate consts in different packages",
+			code1: `package package1
+const ConstA = "shared"
+const ConstB = "shared"
+`,
+			code2: `package package2
+const (
+	ConstC = "shared"
+	ConstD = "shared"
+	ConstE= "unique"
+)`,
+			config: &Config{
+				FindDuplicates: true,
+			},
+			expectedIssues:          3,
+			expectedStr:             "shared",
+			expectedOccurrenceCount: 0,
+		},
 	}
 
-	f2, err := parser.ParseFile(fset, "file2.go", code2, 0)
-	if err != nil {
-		t.Fatalf("Failed to parse test code: %v", err)
-	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
 
-	config := &Config{
-		MinStringLength: 3,
-		MinOccurrences:  2,
-	}
+			fset := token.NewFileSet()
+			f1, err := parser.ParseFile(fset, "file1.go", tt.code1, 0)
+			if err != nil {
+				t.Fatalf("Failed to parse test code: %v", err)
+			}
 
-	issues, err := Run([]*ast.File{f1, f2}, fset, config)
-	if err != nil {
-		t.Fatalf("Run() error = %v", err)
-	}
+			f2, err := parser.ParseFile(fset, "file2.go", tt.code2, 0)
+			if err != nil {
+				t.Fatalf("Failed to parse test code: %v", err)
+			}
 
-	// Should find "shared" appearing 3 times across both files
-	if len(issues) != 1 {
-		t.Fatalf("Expected 1 issue, got %d", len(issues))
-	}
+			issues, err := Run([]*ast.File{f1, f2}, fset, tt.config)
+			if err != nil {
+				t.Fatalf("Run() error = %v", err)
+			}
 
-	issue := issues[0]
-	if issue.Str != "shared" {
-		t.Errorf("Issue.Str = %v, want %v", issue.Str, "shared")
-	}
-	if issue.OccurrencesCount != 3 {
-		t.Errorf("Issue.OccurrencesCount = %v, want 3", issue.OccurrencesCount)
+			// Should find "shared" appearing 3 times across both files
+			if len(issues) != tt.expectedIssues {
+				t.Fatalf("Expected %d issue, got %d", tt.expectedIssues, len(issues))
+			}
+
+			if len(issues) > 0 {
+				issue := issues[0]
+				if issue.Str != tt.expectedStr {
+					t.Errorf("Issue.Str = %v, want %v", issue.Str, tt.expectedStr)
+				}
+
+				if issue.OccurrencesCount != tt.expectedOccurrenceCount {
+					t.Errorf("Issue.OccurrencesCount = %v, want %d", issue.OccurrencesCount, tt.expectedOccurrenceCount)
+				}
+			}
+		})
 	}
 }
 

benchmarks_test.go

@@ -81,6 +81,7 @@ func BenchmarkParseTree(b *testing.B) {
 				false, // ignoreTests
 				false, // matchConstant
 				false, // numbers
+				true,  // findDuplicates
 				0,     // numberMin
 				0,     // numberMax
 				3,     // minLength
@@ -104,6 +105,7 @@ func BenchmarkParseTree(b *testing.B) {
 				false, // ignoreTests
 				false, // matchConstant
 				true,  // numbers
+				true,  // findDuplicates
 				0,     // numberMin
 				0,     // numberMax
 				3,     // minLength
@@ -127,6 +129,7 @@ func BenchmarkParseTree(b *testing.B) {
 				false, // ignoreTests
 				true,  // matchConstant
 				false, // numbers
+				true,  // findDuplicates
 				0,     // numberMin
 				0,     // numberMax
 				3,     // minLength
@@ -157,6 +160,7 @@ func BenchmarkParallelProcessing(b *testing.B) {
 					false,
 					false,
 					true,
+					true,
 					0,
 					0,
 					3,
@@ -304,6 +308,7 @@ func helperFunction%d() string {
 				false,
 				false,
 				true,
+				true,
 				0,
 				0,
 				3,
@@ -332,6 +337,7 @@ func helperFunction%d() string {
 				false,
 				false,
 				true,
+				true,
 				0,
 				0,
 				3,
@@ -377,7 +383,7 @@ func BenchmarkFileReadingPerformance(b *testing.B) {
 
 		// Benchmark the optimized file reading
 		b.Run(fmt.Sprintf("OptimizedIO_%d", size), func(b *testing.B) {
-			parser := New("", "", "", false, false, false, 0, 0, 3, 2, make(map[Type]bool))
+			parser := New("", "", "", false, false, false, true, 0, 0, 3, 2, make(map[Type]bool))
 			b.ResetTimer()
 
 			for i := 0; i < b.N; i++ {

cmd/goconst/main.go

@@ -26,6 +26,7 @@ Flags:
   -min-occurrences   report from how many occurrences (default: 2)
   -min-length        only report strings with the minimum given length (default: 3)
   -match-constant    look for existing constants matching the strings
+  -find-duplicates   look for constants with identical values
   -numbers           search also for duplicated numbers
   -min               minimum value, only works with -numbers
   -max               maximum value, only works with -numbers
@@ -49,6 +50,7 @@ var (
 	flagMinOccurrences = flag.Int("min-occurrences", 2, "report from how many occurrences")
 	flagMinLength      = flag.Int("min-length", 3, "only report strings with the minimum given length")
 	flagMatchConstant  = flag.Bool("match-constant", false, "look for existing constants matching the strings")
+	flagFindDuplicates = flag.Bool("find-duplicates", false, "look for constants with duplicated values")
 	flagNumbers        = flag.Bool("numbers", false, "search also for duplicated numbers")
 	flagMin            = flag.Int("min", 0, "minimum value, only works with -numbers")
 	flagMax            = flag.Int("max", 0, "maximum value, only works with -numbers")
@@ -98,6 +100,7 @@ func run(path string) (bool, error) {
 		*flagIgnoreTests,
 		*flagMatchConstant,
 		*flagNumbers,
+		*flagFindDuplicates,
 		*flagMin,
 		*flagMax,
 		*flagMinLength,
@@ -139,7 +142,7 @@ func printOutput(strs goconst.Strings, consts goconst.Constants, output string)
 		for str, item := range strs {
 			for _, xpos := range item {
 				fmt.Printf(
-					`%s:%d:%d:%d other occurrence(s) of "%s" found in: %s`,
+					`%s:%d:%d:%d other occurrence(s) of %q found in: %s`,
 					xpos.Filename,
 					xpos.Line,
 					xpos.Column,
@@ -157,10 +160,19 @@ func printOutput(strs goconst.Strings, consts goconst.Constants, output string)
 			if len(consts) == 0 {
 				continue
 			}
-			if cst, ok := consts[str]; ok {
+			if csts, ok := consts[str]; ok && len(csts) > 0 {
 				// const should be in the same package and exported
-				fmt.Printf(`A matching constant has been found for "%s": %s`, str, cst.Name)
-				fmt.Printf("\n\t%s\n", cst.String())
+				fmt.Printf(`A matching constant has been found for %q: %s`, str, csts[0].Name)
+				fmt.Printf("\n\t%s\n", csts[0].String())
+			}
+		}
+		for val, csts := range consts {
+			if len(csts) > 1 {
+				fmt.Printf("Duplicate constant(s) with value %q have been found:\n", val)
+
+				for i := 0; i < len(csts); i++ {
+					fmt.Printf("\t%s: %s\n", csts[i].String(), csts[i].Name)
+				}
 			}
 		}
 	default:

integration_test.go

@@ -14,6 +14,7 @@ func TestIntegrationWithTestdata(t *testing.T) {
 		numberMin       int
 		numberMax       int
 		minLength       int
+		findDuplicates  bool
 		minOccurrences  int
 		expectedStrings int
 	}{
@@ -80,6 +81,7 @@ func TestIntegrationWithTestdata(t *testing.T) {
 				tt.ignoreTests,
 				tt.matchConstant,
 				tt.numbers,
+				tt.findDuplicates,
 				tt.numberMin,
 				tt.numberMax,
 				tt.minLength,
@@ -140,6 +142,7 @@ func TestIntegrationExcludeTypes(t *testing.T) {
 				false, // ignoreTests
 				false, // matchConstant
 				false, // numbers
+				false, // findDuplicates
 				0,     // numberMin
 				0,     // numberMax
 				3,     // minLength