internal/lsp: search for deep completions across function calls

We now continue deep completion search across function calls. The
function must take no arguments and return a single argument. For
example, when completing "fo<>" you might get candidates such as
"foo.bar().baz()".

Previously we would stop searching for deep completions when we hit a
function call. For example, we would stop at "foo.bar()", never
finding "foo.bar().baz()". At the time I was worried about the search
scope growing too large, but now that we dynamically limit the search
scope there isn't much left to worry about.

Change-Id: I48772c154400662876682503c1f58ef6e3dca688
Reviewed-on: https://go-review.googlesource.com/c/tools/+/201222
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>

internal/lsp/source/deep_completion.go

@@ -39,10 +39,16 @@ type deepCompletionState struct {
 	candidateCount int
 }
 
-// push pushes obj onto our search stack.
-func (s *deepCompletionState) push(obj types.Object) {
+// push pushes obj onto our search stack. If invoke is true then
+// invocation parens "()" will be appended to the object name.
+func (s *deepCompletionState) push(obj types.Object, invoke bool) {
 	s.chain = append(s.chain, obj)
-	s.chainNames = append(s.chainNames, obj.Name())
+
+	name := obj.Name()
+	if invoke {
+		name += "()"
+	}
+	s.chainNames = append(s.chainNames, name)
 }
 
 // pop pops the last object off our search stack.
@@ -156,8 +162,21 @@ func (c *completer) deepSearch(obj types.Object) {
 		return
 	}
 
+	if sig, ok := obj.Type().Underlying().(*types.Signature); ok {
+		// If obj is a function that takes no arguments and returns one
+		// value, keep searching across the function call.
+		if sig.Params().Len() == 0 && sig.Results().Len() == 1 {
+			// Pass invoke=true since the function needs to be invoked in
+			// the deep chain.
+			c.deepState.push(obj, true)
+			// The result of a function call is not addressable.
+			c.methodsAndFields(sig.Results().At(0).Type(), false)
+			c.deepState.pop()
+		}
+	}
+
 	// Push this object onto our search stack.
-	c.deepState.push(obj)
+	c.deepState.push(obj, false)
 
 	switch obj := obj.(type) {
 	case *types.PkgName:

internal/lsp/testdata/deep/deep.go

@@ -88,3 +88,38 @@ func _() {
 	var i int
 	i = a //@deep(" //", deepAD, deepABC, deepA, deepAB)
 }
+
+type foo struct {
+	b bar
+}
+
+func (f foo) bar() bar {
+	return f.b
+}
+
+func (f foo) barPtr() *bar {
+	return &f.b
+}
+
+type bar struct{}
+
+func (b bar) valueReceiver() int {
+	return 0
+}
+
+func (b *bar) ptrReceiver() int {
+	return 0
+}
+
+func _() {
+	var (
+		i int
+		f foo
+	)
+
+	f.bar().valueReceiver    //@item(deepBarValue, "f.bar().valueReceiver", "func() int", "method")
+	f.barPtr().valueReceiver //@item(deepBarPtrValue, "f.barPtr().valueReceiver", "func() int", "method")
+	f.barPtr().ptrReceiver   //@item(deepBarPtrPtr, "f.barPtr().ptrReceiver", "func() int", "method")
+
+	i = fb //@fuzzy(" //", deepBarValue, deepBarPtrPtr, deepBarPtrValue)
+}

internal/lsp/testdata/summary.txt.golden

@@ -3,7 +3,7 @@ CompletionsCount = 178
 CompletionSnippetCount = 39
 UnimportedCompletionsCount = 1
 DeepCompletionsCount = 5
-FuzzyCompletionsCount = 6
+FuzzyCompletionsCount = 7
 RankedCompletionsCount = 1
 CaseSensitiveCompletionsCount = 4
 DiagnosticsCount = 21