fix(aip-0134): check word boundaries in synonyms rule (#1564)

* fix(aip-0134): check word boundaries in synonyms rule

The synonyms rule was incorrectly flagging method names like "Settle",
"PatchyClouds", or "PutterAround" because it only checked if the name
started with the synonym prefix ("Set", "Patch", "Put").

This change adds word boundary detection by checking if the character
after the prefix is uppercase (indicating a new word in PascalCase) or
if we've reached the end of the string.

Now "SetBook" correctly fails while "Settle" correctly passes.

* use unicode.IsUpper

* store lengths in vars

* remove redundant length check

Author: eddiesoller

rules/aip0134/synonyms.go

@@ -17,6 +17,7 @@ package aip0134
 import (
 	"fmt"
 	"strings"
+	"unicode"
 
 	"github.com/googleapis/api-linter/v2/lint"
 	"github.com/googleapis/api-linter/v2/locations"
@@ -33,15 +34,20 @@ var synonyms = &lint.MethodRule{
 		name := string(m.Name())
 		for _, syn := range []string{"Patch", "Put", "Set"} {
 			if strings.HasPrefix(name, syn) {
-				return []lint.Problem{{
-					Message: fmt.Sprintf(
-						`%q can be a synonym for "Update". Should this be a Update method?`,
-						syn,
-					),
-					Descriptor: m,
-					Location:   locations.DescriptorName(m),
-					Suggestion: strings.Replace(name, syn, "Update", 1),
-				}}
+				synLen := len(syn)
+				nameLen := len(name)
+				// Check for word boundary: either exact match or next char is uppercase
+				if nameLen == synLen || unicode.IsUpper(rune(name[synLen])) {
+					return []lint.Problem{{
+						Message: fmt.Sprintf(
+							`%q can be a synonym for "Update". Should this be a Update method?`,
+							syn,
+						),
+						Descriptor: m,
+						Location:   locations.DescriptorName(m),
+						Suggestion: strings.Replace(name, syn, "Update", 1),
+					}}
+				}
 			}
 		}
 		return nil

rules/aip0134/synonyms_test.go

@@ -30,6 +30,9 @@ func TestSynonyms(t *testing.T) {
 		{"PutBook", testutils.Problems{{Suggestion: "UpdateBook"}}},
 		{"SetBook", testutils.Problems{{Suggestion: "UpdateBook"}}},
 		{"SetIamPolicy", nil},
+		{"Settle", testutils.Problems{}},
+		{"PatchyClouds", testutils.Problems{}},
+		{"PutterAround", testutils.Problems{}},
 	}
 	for _, test := range tests {
 		t.Run(test.MethodName, func(t *testing.T) {