From 1a87bd51fed86bdabb47a5b6072a9cbfd87b5fdd Mon Sep 17 00:00:00 2001
From: Boston Cartwright <boston.cartwright@vasion.com>
Date: Tue, 22 Oct 2024 10:59:33 -0600
Subject: [PATCH] fix: import and arg collision

---
 .../import_collision/internalpackage/foo.go   |  3 +
 .../tests/import_collision/p2/mocks/mocks.go  | 55 +++++++++++++++++++
 .../internal/tests/import_collision/p2/p2.go  | 12 ++++
 mockgen/mockgen.go                            | 18 +++++-
 4 files changed, 86 insertions(+), 2 deletions(-)
 create mode 100644 mockgen/internal/tests/import_collision/internalpackage/foo.go
 create mode 100644 mockgen/internal/tests/import_collision/p2/mocks/mocks.go
 create mode 100644 mockgen/internal/tests/import_collision/p2/p2.go

diff --git a/mockgen/internal/tests/import_collision/internalpackage/foo.go b/mockgen/internal/tests/import_collision/internalpackage/foo.go
new file mode 100644
index 0000000..eaedd5b
--- /dev/null
+++ b/mockgen/internal/tests/import_collision/internalpackage/foo.go
@@ -0,0 +1,3 @@
+package internalpackage
+
+type FooExported struct{}
diff --git a/mockgen/internal/tests/import_collision/p2/mocks/mocks.go b/mockgen/internal/tests/import_collision/p2/mocks/mocks.go
new file mode 100644
index 0000000..3b8fca6
--- /dev/null
+++ b/mockgen/internal/tests/import_collision/p2/mocks/mocks.go
@@ -0,0 +1,55 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: go.uber.org/mock/mockgen/internal/tests/import_collision/p2 (interfaces: Mything)
+//
+// Generated by this command:
+//
+//	mockgen -destination=mocks/mocks.go -package=internalpackage . Mything
+//
+
+// Package internalpackage is a generated GoMock package.
+package internalpackage
+
+import (
+	reflect "reflect"
+
+	gomock "go.uber.org/mock/gomock"
+	internalpackage "go.uber.org/mock/mockgen/internal/tests/import_collision/internalpackage"
+)
+
+// MockMything is a mock of Mything interface.
+type MockMything struct {
+	ctrl     *gomock.Controller
+	recorder *MockMythingMockRecorder
+	isgomock struct{}
+}
+
+// MockMythingMockRecorder is the mock recorder for MockMything.
+type MockMythingMockRecorder struct {
+	mock *MockMything
+}
+
+// NewMockMything creates a new mock instance.
+func NewMockMything(ctrl *gomock.Controller) *MockMything {
+	mock := &MockMything{ctrl: ctrl}
+	mock.recorder = &MockMythingMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockMything) EXPECT() *MockMythingMockRecorder {
+	return m.recorder
+}
+
+// DoThat mocks base method.
+func (m *MockMything) DoThat(arg0 int) internalpackage.FooExported {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "DoThat", arg0)
+	ret0, _ := ret[0].(internalpackage.FooExported)
+	return ret0
+}
+
+// DoThat indicates an expected call of DoThat.
+func (mr *MockMythingMockRecorder) DoThat(arg0 any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DoThat", reflect.TypeOf((*MockMything)(nil).DoThat), arg0)
+}
diff --git a/mockgen/internal/tests/import_collision/p2/p2.go b/mockgen/internal/tests/import_collision/p2/p2.go
new file mode 100644
index 0000000..e6200b7
--- /dev/null
+++ b/mockgen/internal/tests/import_collision/p2/p2.go
@@ -0,0 +1,12 @@
+package p2
+
+//go:generate mockgen -destination=mocks/mocks.go -package=internalpackage . Mything
+
+import (
+	"go.uber.org/mock/mockgen/internal/tests/import_collision/internalpackage"
+)
+
+type Mything interface {
+	// issue here, is that the variable has the same name as an imported package.
+	DoThat(internalpackage int) internalpackage.FooExported
+}
diff --git a/mockgen/mockgen.go b/mockgen/mockgen.go
index b5365de..4353fb8 100644
--- a/mockgen/mockgen.go
+++ b/mockgen/mockgen.go
@@ -766,16 +766,30 @@ func (g *generator) getArgNames(m *model.Method, in bool) []string {
 		params = m.Out
 	}
 	argNames := make([]string, len(params))
+
+	// check if the name already exists as an imported package name
+	// which would cause a name collision
+	nameExistsAsPackage := func(name string) bool {
+		for _, symbolName := range g.packageMap {
+			if symbolName == name {
+				return true
+			}
+		}
+		return false
+	}
+
 	for i, p := range params {
 		name := p.Name
-		if name == "" || name == "_" {
+
+		if name == "" || name == "_" || nameExistsAsPackage(name) {
 			name = fmt.Sprintf("arg%d", i)
 		}
 		argNames[i] = name
 	}
 	if m.Variadic != nil && in {
 		name := m.Variadic.Name
-		if name == "" {
+
+		if name == "" || nameExistsAsPackage(name) {
 			name = fmt.Sprintf("arg%d", len(params))
 		}
 		argNames = append(argNames, name)