internal/lsp/source/completion: add conventional acronyms for type names

This change adds a list of conventional acronyms that are used for function
completion. For example, "err" for "error" and "tx" for "sql.Tx" or "sqlx.Tx".

Fixes golang/go#48260

Change-Id: Iff951ee58c0c95389d474cc45dfd84b483ff71e3
GitHub-Last-Rev: 05ccd5a2fe95e2e0504d28230308c4888477a977
GitHub-Pull-Request: golang/tools#363
Reviewed-on: https://go-review.googlesource.com/c/tools/+/381969
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>

internal/lsp/source/completion/literal.go

@@ -294,6 +294,15 @@ func (c *completer) functionLiteral(ctx context.Context, sig *types.Signature, m
 	})
 }
 
+// conventionalAcronyms contains conventional acronyms for type names
+// in lower case. For example, "ctx" for "context" and "err" for "error".
+var conventionalAcronyms = map[string]string{
+	"context":        "ctx",
+	"error":          "err",
+	"tx":             "tx",
+	"responsewriter": "w",
+}
+
 // abbreviateTypeName abbreviates type names into acronyms. For
 // example, "fooBar" is abbreviated "fb". Care is taken to ignore
 // non-identifier runes. For example, "[]int" becomes "i", and
@@ -320,6 +329,10 @@ func abbreviateTypeName(s string) string {
 		return !unicode.IsLetter(r)
 	})
 
+	if acr, ok := conventionalAcronyms[strings.ToLower(s)]; ok {
+		return acr
+	}
+
 	for i, r := range s {
 		// Stop if we encounter a non-identifier rune.
 		if !unicode.IsLetter(r) && !unicode.IsNumber(r) {

internal/lsp/testdata/snippets/literal_snippets.go.in

@@ -2,6 +2,7 @@ package snippets
 
 import (
 	"bytes"
+	"context"
 	"go/ast"
 	"net/http"
 	"sort"
@@ -137,14 +138,14 @@ func _() {
 
 	sort.Slice(nil, fun) //@complete(")", litFunc),snippet(")", litFunc, "func(i, j int) bool {$0\\}", "func(i, j int) bool {$0\\}")
 
-	http.HandleFunc("", f) //@snippet(")", litFunc, "func(rw http.ResponseWriter, r *http.Request) {$0\\}", "func(${1:rw} http.ResponseWriter, ${2:r} *http.Request) {$0\\}")
+	http.HandleFunc("", f) //@snippet(")", litFunc, "func(w http.ResponseWriter, r *http.Request) {$0\\}", "func(${1:w} http.ResponseWriter, ${2:r} *http.Request) {$0\\}")
 
 	// no literal "func" completions
 	http.Handle("", fun) //@complete(")")
 
 	http.HandlerFunc() //@item(handlerFunc, "http.HandlerFunc()", "", "var")
 	http.Handle("", h) //@snippet(")", handlerFunc, "http.HandlerFunc($0)", "http.HandlerFunc($0)")
-	http.Handle("", http.HandlerFunc()) //@snippet("))", litFunc, "func(rw http.ResponseWriter, r *http.Request) {$0\\}", "func(${1:rw} http.ResponseWriter, ${2:r} *http.Request) {$0\\}")
+	http.Handle("", http.HandlerFunc()) //@snippet("))", litFunc, "func(w http.ResponseWriter, r *http.Request) {$0\\}", "func(${1:w} http.ResponseWriter, ${2:r} *http.Request) {$0\\}")
 
 	var namedReturn func(s string) (b bool)
 	namedReturn = f //@snippet(" //", litFunc, "func(s string) (b bool) {$0\\}", "func(s string) (b bool) {$0\\}")
@@ -167,6 +168,11 @@ func _() {
 	builtinTypes = f //@snippet(" //", litFunc, "func(i1 []int, b [two]bool, m map[string]string, s struct{ i int \\}, i2 interface{ foo() \\}, c <-chan int) {$0\\}", "func(${1:i1} []int, ${2:b} [two]bool, ${3:m} map[string]string, ${4:s} struct{ i int \\}, ${5:i2} interface{ foo() \\}, ${6:c} <-chan int) {$0\\}")
 
 	var _ func(ast.Node) = f //@snippet(" //", litFunc, "func(n ast.Node) {$0\\}", "func(${1:n} ast.Node) {$0\\}")
+	var _ func(error) = f //@snippet(" //", litFunc, "func(err error) {$0\\}", "func(${1:err} error) {$0\\}")
+	var _ func(context.Context) = f //@snippet(" //", litFunc, "func(ctx context.Context) {$0\\}", "func(${1:ctx} context.Context) {$0\\}")
+
+	type context struct {}
+	var _ func(context) = f //@snippet(" //", litFunc, "func(ctx context) {$0\\}", "func(${1:ctx} context) {$0\\}")
 }
 
 func _() {

internal/lsp/testdata/summary.txt.golden

@@ -2,7 +2,7 @@
 CallHierarchyCount = 2
 CodeLensCount = 5
 CompletionsCount = 265
-CompletionSnippetCount = 103
+CompletionSnippetCount = 106
 UnimportedCompletionsCount = 5
 DeepCompletionsCount = 5
 FuzzyCompletionsCount = 8

internal/lsp/testdata/summary_go1.18.txt.golden

@@ -2,7 +2,7 @@
 CallHierarchyCount = 2
 CodeLensCount = 5
 CompletionsCount = 266
-CompletionSnippetCount = 104
+CompletionSnippetCount = 107
 UnimportedCompletionsCount = 5
 DeepCompletionsCount = 5
 FuzzyCompletionsCount = 8