importas: allow multiple empty aliases (#5222)

pkg/golinters/importas/importas.go

@@ -51,8 +51,11 @@ func New(settings *config.ImportAsSettings) *goanalysis.Linter {
 				uniqPackages[a.Pkg] = a
 			}
 
-			// skip the duplication check when the alias is a regular expression replacement pattern (ie. contains `$`).
-			if v, ok := uniqAliases[a.Alias]; ok && !strings.Contains(a.Alias, "$") {
+			// Skips the duplication check when:
+			// - the alias is empty.
+			// - the alias is a regular expression replacement pattern (ie. contains `$`).
+			v, ok := uniqAliases[a.Alias]
+			if ok && a.Alias != "" && !strings.Contains(a.Alias, "$") {
 				lintCtx.Log.Errorf("invalid configuration, multiple packages with the same alias: alias=%s packages=[%s,%s]", a.Alias, a.Pkg, v.Pkg)
 			} else {
 				uniqAliases[a.Alias] = a

pkg/golinters/importas/testdata/importas_several_empty_aliases.go

@@ -0,0 +1,16 @@
+//golangcitest:args -Eimportas
+//golangcitest:config_path testdata/importas_several_empty_aliases.yml
+//golangcitest:expected_exitcode 0
+package testdata
+
+import (
+	"fmt"
+	"math"
+	"os"
+)
+
+func _() {
+	fmt.Println("a")
+	fmt.Fprint(os.Stderr, "b")
+	println(math.MaxInt)
+}

pkg/golinters/importas/testdata/importas_several_empty_aliases.yml

@@ -0,0 +1,9 @@
+linters-settings:
+  importas:
+    alias:
+      - pkg: fmt
+        alias: ''
+      - pkg: os
+        alias: ''
+      - pkg: math
+        alias: ''