internal/lsp: use TypecheckCgo when possible

When on 1.15+, enable TypecheckCgo. This improves cgo support
significantly, but we'll still have trouble with newly-referenced C
identifiers and changes to the magic comment.

Updates golang/go#35721.

Change-Id: I44dc95ce2d91d552e1e66e3722dc4230ab59fedd
Reviewed-on: https://go-review.googlesource.com/c/tools/+/229779
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cache/snapshot.go

@@ -9,8 +9,10 @@ import (
 	"fmt"
 	"go/ast"
 	"go/token"
+	"go/types"
 	"os"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"strings"
 	"sync"
@@ -118,6 +120,10 @@ func (s *snapshot) Config(ctx context.Context) *packages.Config {
 		},
 		Tests: true,
 	}
+	// We want to type check cgo code if go/types supports it.
+	if reflect.ValueOf(&types.Config{}).Elem().FieldByName("UsesCgo").IsValid() {
+		cfg.Mode |= packages.TypecheckCgo
+	}
 	packagesinternal.SetGoCmdRunner(cfg, s.view.gocmdRunner)
 
 	return cfg

internal/lsp/testdata/lsp/primarymod/cgo/declarecgo.go

@@ -10,9 +10,10 @@ void myprint(char* s) {
 */
 import "C"
 
-import "fmt"
-
-import "unsafe"
+import (
+	"fmt"
+	"unsafe"
+)
 
 func Example() { //@mark(funccgoexample, "Example"),item(funccgoexample, "Example", "func()", "func")
 	fmt.Println()
@@ -22,5 +23,5 @@ func Example() { //@mark(funccgoexample, "Example"),item(funccgoexample, "Exampl
 }
 
 func _() {
-	Example()
+	Example() //@godef("ample", funccgoexample),complete("ample", funccgoexample)
 }

internal/lsp/testdata/lsp/primarymod/cgo/declarecgo.go.golden

@@ -0,0 +1,30 @@
+-- funccgoexample-definition --
+cgo/declarecgo.go:18:6-13: defined here as ```go
+func Example()
+```
+
+[`cgo.Example` on pkg.go.dev](https://pkg.go.dev/golang.org/x/tools/internal/lsp/cgo#Example)
+-- funccgoexample-definition-json --
+{
+	"span": {
+		"uri": "file://cgo/declarecgo.go",
+		"start": {
+			"line": 18,
+			"column": 6,
+			"offset": 151
+		},
+		"end": {
+			"line": 18,
+			"column": 13,
+			"offset": 158
+		}
+	},
+	"description": "```go\nfunc Example()\n```\n\n[`cgo.Example` on pkg.go.dev](https://pkg.go.dev/golang.org/x/tools/internal/lsp/cgo#Example)"
+}
+
+-- funccgoexample-hover --
+[`cgo.Example` on pkg.go.dev](https://pkg.go.dev/golang.org/x/tools/internal/lsp/cgo#Example)
+
+```go
+func Example()
+```

internal/lsp/testdata/lsp/primarymod/cgo/declarecgo_nocgo.go

@@ -3,4 +3,4 @@
 package cgo
 
 // Set a dummy marker to keep the test framework happy. The tests should be skipped.
-var _ = "Example" //@mark(funccgoexample, "Example")
+var _ = "Example" //@mark(funccgoexample, "Example"),godef("ample", funccgoexample),complete("ample", funccgoexample)

internal/lsp/testdata/lsp/primarymod/cgoimport/usecgo.go.golden

@@ -1,5 +1,5 @@
 -- funccgoexample-definition --
-cgo/declarecgo.go:17:6-13: defined here as ```go
+cgo/declarecgo.go:18:6-13: defined here as ```go
 func cgo.Example()
 ```
 
@@ -9,14 +9,14 @@ func cgo.Example()
 	"span": {
 		"uri": "file://cgo/declarecgo.go",
 		"start": {
-			"line": 17,
+			"line": 18,
 			"column": 6,
-			"offset": 153
+			"offset": 151
 		},
 		"end": {
-			"line": 17,
+			"line": 18,
 			"column": 13,
-			"offset": 160
+			"offset": 158
 		}
 	},
 	"description": "```go\nfunc cgo.Example()\n```\n\n[`cgo.Example` on pkg.go.dev](https://pkg.go.dev/golang.org/x/tools/internal/lsp/cgo#Example)"

internal/lsp/testdata/lsp/summary.txt.golden

@@ -1,6 +1,6 @@
 -- summary --
 CodeLensCount = 4
-CompletionsCount = 240
+CompletionsCount = 241
 CompletionSnippetCount = 76
 UnimportedCompletionsCount = 6
 DeepCompletionsCount = 5
@@ -12,7 +12,7 @@ FoldingRangesCount = 2
 FormatCount = 6
 ImportCount = 8
 SuggestedFixCount = 6
-DefinitionsCount = 50
+DefinitionsCount = 51
 TypeDefinitionsCount = 2
 HighlightsCount = 52
 ReferencesCount = 11

internal/lsp/tests/tests.go

@@ -230,7 +230,10 @@ func DefaultOptions() source.Options {
 	return o
 }
 
-var haveCgo = false
+var (
+	haveCgo = false
+	go115   = false
+)
 
 // Load creates the folder structure required when testing with modules.
 // The directory structure of a test needs to look like the example below:
@@ -453,6 +456,9 @@ func Run(t *testing.T, tests Tests, data *Data) {
 					if (!haveCgo || runtime.GOOS == "android") && strings.Contains(t.Name(), "cgo") {
 						t.Skip("test requires cgo, not supported")
 					}
+					if !go115 && strings.Contains(t.Name(), "declarecgo") {
+						t.Skip("test requires Go 1.15")
+					}
 					test(t, src, e, data.CompletionItems)
 				})
 			}
@@ -611,6 +617,9 @@ func Run(t *testing.T, tests Tests, data *Data) {
 				if (!haveCgo || runtime.GOOS == "android") && strings.Contains(t.Name(), "cgo") {
 					t.Skip("test requires cgo, not supported")
 				}
+				if !go115 && strings.Contains(t.Name(), "declarecgo") {
+					t.Skip("test requires Go 1.15")
+				}
 				tests.Definition(t, spn, d)
 			})
 		}
@@ -809,7 +818,7 @@ func checkData(t *testing.T, data *Data) {
 	}))
 	got := buf.String()
 	if want != got {
-		t.Errorf("test summary does not match, want\n%s\ngot:\n%s", want, got)
+		t.Errorf("test summary does not match: %v", Diff(want, got))
 	}
 }
 

internal/lsp/tests/tests_go115.go

@@ -0,0 +1,7 @@
+// +build go1.15
+
+package tests
+
+func init() {
+	go115 = true
+}