Compute and use constant expressions via the type checker. (#35)

* Support for constant expressions

* handle constant expressions via typechecker

* fix: type check in batches processor

* fix: type-checking concurrently is not supported

---------

Co-authored-by: Jonathan Gautheron <[email protected]>

Author: kalexmills

api.go

@@ -3,6 +3,7 @@ package goconst
 import (
 	"go/ast"
 	"go/token"
+	"go/types"
 	"sort"
 	"strings"
 	"sync"
@@ -64,16 +65,18 @@ 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 enables finding constants whose values match existing constants in other packages.
 	FindDuplicates bool
+	// EvalConstExpressions enables evaluation of constant expressions like Prefix + "suffix"
+	EvalConstExpressions bool
 }
 
 // NewWithIgnorePatterns creates a new instance of the parser with support for multiple ignore patterns.
 // This is an alternative constructor that takes a slice of ignore string patterns.
 func NewWithIgnorePatterns(
 	path, ignore string,
 	ignoreStrings []string,
-	ignoreTests, matchConstant, numbers, findDuplicates bool,
+	ignoreTests, matchConstant, numbers, findDuplicates, evalConstExpressions bool,
 	numberMin, numberMax, minLength, minOccurrences int,
 	excludeTypes map[Type]bool) *Parser {
 
@@ -101,6 +104,7 @@ func NewWithIgnorePatterns(
 		matchConstant,
 		numbers,
 		findDuplicates,
+		evalConstExpressions,
 		numberMin,
 		numberMax,
 		minLength,
@@ -111,7 +115,7 @@ func NewWithIgnorePatterns(
 
 // RunWithConfig is a convenience function that runs the analysis with a Config object
 // directly supporting multiple ignore patterns.
-func RunWithConfig(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue, error) {
+func RunWithConfig(files []*ast.File, fset *token.FileSet, typeInfo *types.Info, cfg *Config) ([]Issue, error) {
 	p := NewWithIgnorePatterns(
 		"",
 		"",
@@ -120,6 +124,7 @@ func RunWithConfig(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue
 		cfg.MatchWithConstants,
 		cfg.ParseNumbers,
 		cfg.FindDuplicates,
+		cfg.EvalConstExpressions,
 		cfg.NumberMin,
 		cfg.NumberMax,
 		cfg.MinStringLength,
@@ -176,9 +181,9 @@ func RunWithConfig(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue
 			ast.Walk(&treeVisitor{
 				fileSet:     fset,
 				packageName: emptyStr,
-				fileName:    emptyStr,
 				p:           p,
 				ignoreRegex: p.ignoreStringsRegex,
+				typeInfo:    typeInfo,
 			}, f)
 		}(f)
 	}
@@ -277,6 +282,6 @@ func RunWithConfig(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue
 // Run analyzes the provided AST files for duplicated strings or numbers
 // according to the provided configuration.
 // It returns a slice of Issue objects containing the findings.
-func Run(files []*ast.File, fset *token.FileSet, cfg *Config) ([]Issue, error) {
-	return RunWithConfig(files, fset, cfg)
+func Run(files []*ast.File, fset *token.FileSet, typeInfo *types.Info, cfg *Config) ([]Issue, error) {
+	return RunWithConfig(files, fset, typeInfo, cfg)
 }

api_test.go

@@ -4,6 +4,7 @@ import (
 	"go/ast"
 	"go/parser"
 	"go/token"
+	"go/types"
 	"testing"
 )
 
@@ -53,6 +54,20 @@ func example() {
 			},
 			expectedIssues: 1,
 		},
+		{
+			name: "duplicate computed consts",
+			code: `package example
+const ConstA = "te"
+const Test = "test"
+func example() {
+	const ConstB = ConstA + "st"
+}`,
+			config: &Config{
+				FindDuplicates:       true,
+				EvalConstExpressions: true,
+			},
+			expectedIssues: 1,
+		},
 		{
 			name: "string duplication with ignore",
 			code: `package example
@@ -164,7 +179,10 @@ func example() {
 				t.Fatalf("Failed to parse test code: %v", err)
 			}
 
-			issues, err := Run([]*ast.File{f}, fset, tt.config)
+			chkr, info := checker(fset)
+			_ = chkr.Files([]*ast.File{f})
+
+			issues, err := Run([]*ast.File{f}, fset, info, tt.config)
 			if err != nil {
 				t.Fatalf("Run() error = %v", err)
 			}
@@ -201,7 +219,10 @@ func example() {
 		MatchWithConstants: true,
 	}
 
-	issues, err := Run([]*ast.File{f}, fset, config)
+	chkr, info := checker(fset)
+	_ = chkr.Files([]*ast.File{f})
+
+	issues, err := Run([]*ast.File{f}, fset, info, config)
 	if err != nil {
 		t.Fatalf("Run() error = %v", err)
 	}
@@ -256,16 +277,16 @@ func example2() {
 			expectedOccurrenceCount: 3,
 		},
 		{
-			name: "duplicate consts in different packages",
-			code1: `package package1
+			name: "duplicate consts in different files",
+			code1: `package example
 const ConstA = "shared"
 const ConstB = "shared"
 `,
-			code2: `package package2
+			code2: `package example
 const (
 	ConstC = "shared"
 	ConstD = "shared"
-	ConstE= "unique"
+	ConstE = "unique"
 )`,
 			config: &Config{
 				FindDuplicates: true,
@@ -290,7 +311,10 @@ const (
 				t.Fatalf("Failed to parse test code: %v", err)
 			}
 
-			issues, err := Run([]*ast.File{f1, f2}, fset, tt.config)
+			chkr, info := checker(fset)
+			_ = chkr.Files([]*ast.File{f1, f2})
+
+			issues, err := Run([]*ast.File{f1, f2}, fset, info, tt.config)
 			if err != nil {
 				t.Fatalf("Run() error = %v", err)
 			}
@@ -348,8 +372,10 @@ func allContexts(param string) string {
 		MinStringLength: 3,
 		MinOccurrences:  2,
 	}
+	chkr, info := checker(fset)
+	_ = chkr.Files([]*ast.File{f})
 
-	issues, err := Run([]*ast.File{f}, fset, config)
+	issues, err := Run([]*ast.File{f}, fset, info, config)
 	if err != nil {
 		t.Fatalf("Run() error = %v", err)
 	}
@@ -429,8 +455,10 @@ func multipleContexts() {
 				MinOccurrences:  2,
 				ExcludeTypes:    tt.excludeTypes,
 			}
+			chkr, info := checker(fset)
+			_ = chkr.Files([]*ast.File{f})
 
-			issues, err := Run([]*ast.File{f}, fset, config)
+			issues, err := Run([]*ast.File{f}, fset, info, config)
 			if err != nil {
 				t.Fatalf("Run() error = %v", err)
 			}
@@ -453,3 +481,84 @@ func multipleContexts() {
 		})
 	}
 }
+
+func TestConstExpressions(t *testing.T) {
+	// Test detecting and matching string constants derived from expressions
+	code := `package example
+
+const (
+	Prefix = "example.com/"
+	Label1 = Prefix + "some_label"
+	Label2 = Prefix + "another_label"
+)
+
+func example() {
+	// These should match the constants from expressions
+	a := "example.com/some_label"
+	b := "example.com/some_label"
+	
+	// This should also match
+	web1 := "example.com/another_label"
+	web2 := "example.com/another_label"
+}
+`
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "example.go", code, 0)
+	if err != nil {
+		t.Fatalf("Failed to parse test code: %v", err)
+	}
+
+	config := &Config{
+		MinStringLength:      3,
+		MinOccurrences:       2,
+		MatchWithConstants:   true,
+		EvalConstExpressions: true,
+	}
+	chkr, info := checker(fset)
+	_ = chkr.Files([]*ast.File{f})
+
+	issues, err := Run([]*ast.File{f}, fset, info, config)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+
+	// We expect issues for both labels
+	expectedMatches := map[string]string{
+		"example.com/some_label":    "Label1",
+		"example.com/another_label": "Label2",
+	}
+
+	// Check that we have two issues
+	if len(issues) != 2 {
+		t.Errorf("Expected 2 issues, got %d", len(issues))
+		for _, issue := range issues {
+			t.Logf("Found issue: %q matches constant %q with %d occurrences",
+				issue.Str, issue.MatchingConst, issue.OccurrencesCount)
+		}
+		return
+	}
+
+	// Check that each string matches the expected constant
+	for _, issue := range issues {
+		expectedConst, ok := expectedMatches[issue.Str]
+		if !ok {
+			t.Errorf("Unexpected issue for string: %s", issue.Str)
+			continue
+		}
+
+		if issue.MatchingConst != expectedConst {
+			t.Errorf("For string %q: got matching const %q, want %q",
+				issue.Str, issue.MatchingConst, expectedConst)
+		}
+	}
+}
+
+func checker(fset *token.FileSet) (*types.Checker, *types.Info) {
+	cfg := &types.Config{
+		Error: func(err error) {},
+	}
+	info := &types.Info{
+		Types: make(map[ast.Expr]types.TypeAndValue),
+	}
+	return types.NewChecker(cfg, fset, types.NewPackage("", "example"), info), info
+}