fix: nil panic on old go.mod (issue #1100)

lint/linter.go

@@ -173,6 +173,10 @@ func detectGoMod(dir string) (rootDir string, ver *goversion.Version, err error)
 		return "", nil, fmt.Errorf("failed to parse %q, got %v", modFileName, err)
 	}
 
+	if modAst.Go == nil {
+		return "", nil, fmt.Errorf("%q does not specify a Go version", modFileName)
+	}
+
 	ver, err = goversion.NewVersion(modAst.Go.Version)
 	return filepath.Dir(modFileName), ver, err
 }

test/issue1100_test.go

@@ -0,0 +1,22 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestIssue1100(t *testing.T) {
+	args := []any{map[string]any{
+		"maxLitCount": "2",
+		"allowStrs":   "\"\"",
+		"allowInts":   "0,1,2",
+		"allowFloats": "0.0,1.0",
+		"ignoreFuncs": "os\\.(CreateFile|WriteFile|Chmod|FindProcess),\\.Println,ignoredFunc,\\.Info",
+	}}
+
+	testRule(t, "goUnknown/issue1100", &rule.AddConstantRule{}, &lint.RuleConfig{
+		Arguments: args,
+	})
+}

testdata/goUnknown/go.mod

@@ -0,0 +1,2 @@
+module github.com/mgechev/revive/testdata
+

testdata/goUnknown/issue1100.go

@@ -0,0 +1,104 @@
+package fixtures
+
+import (
+	"context"
+	"fmt"
+	"os"
+)
+
+type testLogger struct{}
+
+func (l *testLogger) Info(ctx context.Context, msg string) {}
+
+func getLogger() *testLogger {
+	return &testLogger{}
+}
+
+func test1007() {
+	getLogger().Info(context.Background(), "test1007")
+	getLogger().Info(context.Background(), "test1007")
+	getLogger().Info(context.Background(), "test1007")
+}
+
+func foo(a float32, b string, c any, d int) {
+	a = 1.0 // ignore
+	b = "ignore"
+	c = 2              // ignore
+	println("lit", 12) // MATCH /avoid magic numbers like '12', create a named constant for it/
+	if a == 12.50 {    // MATCH /avoid magic numbers like '12.50', create a named constant for it/
+		if b == "lit" {
+			c = "lit" // MATCH /string literal "lit" appears, at least, 3 times, create a named constant for it/
+		}
+		for i := 0; i < 1; i++ {
+			println("lit")
+		}
+	}
+
+	println(0666)           // MATCH /avoid magic numbers like '0666', create a named constant for it/
+	os.Chmod("test", 0666)  // ignore
+	os.FindProcess(102100)  // ignore
+	fmt.Println("test", 12) // ignore
+	fmt.Printf("%d", 100)   // MATCH /avoid magic numbers like '100', create a named constant for it/
+	myPrintln("%d", 100)    // MATCH /avoid magic numbers like '100', create a named constant for it/
+	ignoredFunc(1000)       // ignore
+	ignoredFunc1(1000)      // ignore - match regexp too
+
+	println("The result of calling myFunc is: ", ignoredFunc(100))             // ignore
+	println("result is: ", ignoredFunc(notIgnoredFunc(ignoredFunc(100))))      // ignore
+	println("result of calling myFunc is: ", notIgnoredFunc(ignoredFunc(100))) // ignore
+
+	println("result myFunc is: ", notIgnoredFunc(100))           // MATCH /avoid magic numbers like '100', create a named constant for it/
+	println("The result is: ", ignoredFunc(notIgnoredFunc(100))) // MATCH /avoid magic numbers like '100', create a named constant for it/
+}
+
+func myPrintln(s string, num int) {
+
+}
+
+func ignoredFunc1(num int) int {
+	return num
+}
+
+func ignoredFunc(num int) int {
+	return num
+}
+
+func notIgnoredFunc(num int) int {
+	return num
+}
+
+func tagsInStructLiteralsShouldBeOK() {
+	a := struct {
+		X int `json:"x"`
+	}{}
+
+	b := struct {
+		X int `json:"x"`
+	}{}
+
+	c := struct {
+		X int `json:"x"`
+	}{}
+
+	d := struct {
+		X int `json:"x"`
+		Y int `json:"y"`
+	}{}
+
+	e := struct {
+		X int `json:"x"`
+		Y int `json:"y"`
+	}{}
+
+	var f struct {
+		X int `json:"x"`
+		Y int `json:"y"`
+	}
+
+	var g struct {
+		X int `json:"x"`
+		Y int `json:"y"`
+	}
+
+	_, _, _, _, _, _, _ = a, b, c, d, e, f, g
+}