fix: ensure conflicting aliases are handled

Signed-off-by: Piaras Hoban <[email protected]>

Author: phoban01

cmd/cue/cmd/testdata/script/cmd_exp_gengo_alias_conflict.txtar

@@ -0,0 +1,57 @@
+# reproduction for https://github.com/cue-lang/cue/issues/3974
+exec cue exp gengotypes
+cmp cue_types_main_gen.go expect-gengo
+
+-- cue.mod/module.cue --
+module: "mod.test"
+language: version: "v0.13.0"
+
+-- pkg/foo/p1/p1.cue --
+package p1
+
+#Foo: int
+
+-- pkg/bar/p2/p2.cue --
+package p2
+
+#Bar: string
+
+-- f1.cue --
+package main
+
+import (
+	same "mod.test/pkg/foo/p1"
+)
+
+#A: {
+	foo: same.#Foo
+}
+
+-- f2.cue --
+package main
+
+import (
+	same "mod.test/pkg/bar/p2"
+)
+
+#B: {
+	bar: same.#Bar
+}
+
+-- expect-gengo --
+// Code generated by "cue exp gengotypes"; DO NOT EDIT.
+
+package main
+
+import (
+	same1 "mod.test/pkg/bar/p2"
+	same "mod.test/pkg/foo/p1"
+)
+
+type A struct {
+	Foo same.Foo `json:"foo"`
+}
+
+type B struct {
+	Bar same1.Bar `json:"bar"`
+}

internal/encoding/gotypes/generate.go

@@ -231,7 +231,9 @@ type generator struct {
 	// def tracks the generation state for a single CUE definition.
 	def *generatedDef
 
-	// importAliases maps package names to the alias
+	// importAliases maps package names to a given alias. In the case that there are multiple aliases present for
+	// same package then we will use the first alias encountered. When the same alias is used for multiple packages
+	// across different files, then a number will be added to the end of the alias to avoid conflicts.
 	importAliases map[string]string
 }
 
@@ -797,6 +799,7 @@ func emitDocs(printf func(string, ...any), name string, groups []*ast.CommentGro
 // gatherImportAliases collects the aliases from imports across the instance.
 func gatherImportAliases(inst *build.Instance) (map[string]string, error) {
 	fileAliases := make(map[string]string)
+	trackedAliases := make(map[string]int32)
 	for _, f := range inst.Files {
 		for _, s := range f.Imports {
 			if s.Path == nil || s.Name == nil {
@@ -807,7 +810,11 @@ func gatherImportAliases(inst *build.Instance) (map[string]string, error) {
 			if err != nil {
 				return nil, err
 			}
+			if count, found := trackedAliases[alias]; found {
+				alias = fmt.Sprintf("%s%d", alias, count)
+			}
 			fileAliases[path] = alias
+			trackedAliases[alias]++
 		}
 	}
 	return fileAliases, nil