gopls/internal/memoize/memoize

1	// Copyright 2019 The Go Authors. All rights reserved.
2	// Use of this source code is governed by a BSD-style
3	// license that can be found in the LICENSE file.
4
5	package memoize_test
6
7	import (
8	"context"
9	"sync"
10	"testing"
11	"time"
12
13	"golang.org/x/tools/internal/memoize"
14	)
15
16	func TestGet(t *testing.T) {
17	var store memoize.Store
18
19	evaled := 0
20
21	h, release := store.Promise("key", func(context.Context, interface{}) interface{} {
22	evaled++
23	return "res"
24	})
25	defer release()
26	expectGet(t, h, "res")
27	expectGet(t, h, "res")
28	if evaled != 1 {
29	t.Errorf("got %v calls to function, wanted 1", evaled)
30	}
31	}
32
33	func expectGet(t testing.T, h memoize.Promise, wantV interface{}) {
34	t.Helper()
35	gotV, gotErr := h.Get(context.Background(), nil)
36	if gotV != wantV \|\| gotErr != nil {
37	t.Fatalf("Get() = %v, %v, wanted %v, nil", gotV, gotErr, wantV)
38	}
39	}
40
41	func TestNewPromise(t *testing.T) {
42	calls := 0
43	f := func(context.Context, interface{}) interface{} {
44	calls++
45	return calls
46	}
47
48	// All calls to Get on the same promise return the same result.
49	p1 := memoize.NewPromise("debug", f)
50	expectGet(t, p1, 1)
51	expectGet(t, p1, 1)
52
53	// A new promise calls the function again.
54	p2 := memoize.NewPromise("debug", f)
55	expectGet(t, p2, 2)
56	expectGet(t, p2, 2)
57
58	// The original promise is unchanged.
59	expectGet(t, p1, 1)
60	}
61
62	func TestStoredPromiseRefCounting(t *testing.T) {
63	var store memoize.Store
64	v1 := false
65	v2 := false
66	p1, release1 := store.Promise("key1", func(context.Context, interface{}) interface{} {
67	return &v1
68	})
69	p2, release2 := store.Promise("key2", func(context.Context, interface{}) interface{} {
70	return &v2
71	})
72	expectGet(t, p1, &v1)
73	expectGet(t, p2, &v2)
74
75	expectGet(t, p1, &v1)
76	expectGet(t, p2, &v2)
77
78	p2Copy, release2Copy := store.Promise("key2", func(context.Context, interface{}) interface{} {
79	return &v1
80	})
81	if p2 != p2Copy {
82	t.Error("Promise returned a new value while old is not destroyed yet")
83	}
84	expectGet(t, p2Copy, &v2)
85
86	release2()
87	if got, want := v2, false; got != want {
88	t.Errorf("after destroying first v2 ref, got %v, want %v", got, want)
89	}
90	release2Copy()
91	if got, want := v1, false; got != want {
92	t.Errorf("after destroying v2, got %v, want %v", got, want)
93	}
94	release1()
95
96	p2Copy, release2Copy = store.Promise("key2", func(context.Context, interface{}) interface{} {
97	return &v2
98	})
99	if p2 == p2Copy {
100	t.Error("Promise returned previously destroyed value")
101	}
102	release2Copy()
103	}
104
105	func TestPromiseDestroyedWhileRunning(t *testing.T) {
106	// Test that calls to Promise.Get return even if the promise is destroyed while running.
107
108	var store memoize.Store
109	c := make(chan int)
110
111	var v int
112	h, release := store.Promise("key", func(ctx context.Context, _ interface{}) interface{} {
113	<-c
114	<-c
115	if err := ctx.Err(); err != nil {
116	t.Errorf("ctx.Err() = %v, want nil", err)
117	}
118	return &v
119	})
120
121	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second) // arbitrary timeout; may be removed if it causes flakes
122	defer cancel()
123
124	var wg sync.WaitGroup
125	wg.Add(1)
126	var got interface{}
127	var err error
128	go func() {
129	got, err = h.Get(ctx, nil)
130	wg.Done()
131	}()
132
133	c <- 0 // send once to enter the promise function
134	release() // release before the promise function returns
135	c <- 0 // let the promise function proceed
136
137	wg.Wait()
138
139	if err != nil {
140	t.Errorf("Get() failed: %v", err)
141	}
142	if got != &v {
143	t.Errorf("Get() = %v, want %v", got, v)
144	}
145	}
146
147	func TestDoubleReleasePanics(t *testing.T) {
148	var store memoize.Store
149	_, release := store.Promise("key", func(ctx context.Context, _ interface{}) interface{} { return 0 })
150
151	panicked := false
152
153	func() {
154	defer func() {
155	if recover() != nil {
156	panicked = true
157	}
158	}()
159	release()
160	release()
161	}()
162
163	if !panicked {
164	t.Errorf("calling release() twice did not panic")
165	}
166	}
167