Keep initialisms after leading digits

docs/naming.md

@@ -10,9 +10,9 @@ each rename.
 |---|---|---|
 | `client_address`, `client-address`, `client.address` | `ClientAddress` | Any character that is not a letter or a digit splits words, apart from the symbols below. |
 | `fooBar`, `HTTPServer` | `FooBar`, `HTTPServer` | A capital starts a word. An upper-case run ends before its last capital when a lower-case letter follows. |
-| `v2api`, `404NotFound` | `V2API`, `N404NotFound` | Digits stay with the word before them. A letter after them starts a new word. |
+| `v2api`, `404NotFound` | `V2API`, `N404NotFound` | Digits stay with the word before them. A letter after them starts a new word, unless the word starts with the digits: `1st` stays one word. |
 | `CLIENT_ADDRESS`, `SSN` | `ClientAddress`, `Ssn` | Every word is written with one capital, unless it is an initialism. |
-| `userId`, `urls`, `userIDs`, `id2` | `UserID`, `URLs`, `UserIDs`, `ID2` | Initialisms stay upper case, also with a plural `s` or trailing digits. |
+| `userId`, `urls`, `userIDs`, `id2`, `short_2url` | `UserID`, `URLs`, `UserIDs`, `ID2`, `Short2URL` | Initialisms stay upper case, also with a plural `s` or digits before or after them. |
 | `1st`, `200` | `N1st`, `N200` | A name that would start with a digit gets `N` in front. |
 | `+1`, `-1`, `-created_at`, `@type` | `Plus1`, `Minus1`, `MinusCreatedAt`, `AtType` | `+` and `@` become words anywhere, `-` only at the start. |
 | `1.5`, `v1.2` | `N1Dot5`, `V1Dot2` | A dot between two digits becomes `Dot`. |
@@ -39,7 +39,8 @@ naming:
 ```
 
 An initialism matches a whole word in any case: `Id`, `id` and `ID` all give `ID`. It does not
-match inside a word, so `userid` stays `Userid`.
+match inside a word, so `userid` stays `Userid`. Digits in front do not stop it: with `DS` listed,
+`force_3ds_flow` gives `Force3DSFlow`.
 
 ## Names for types without a name
 

internal/naming/namer.go

@@ -241,22 +241,35 @@ func (n *Namer) camel(part string) string {
 	return b.String()
 }
 
-// caseWord keeps initialisms canonical, also with a plural "s" or trailing digits: IDs, HTTP2.
+// caseWord keeps initialisms canonical, also after leading digits: IDs, HTTP2, 3DS.
 func (n *Namer) caseWord(w string) string {
 	lw := strings.ToLower(w)
-	if c, ok := n.initialisms[lw]; ok {
+	if c, ok := n.initialism(lw); ok {
 		return c
 	}
 
+	rest := strings.TrimLeft(lw, "0123456789")
+	if c, ok := n.initialism(rest); ok {
+		return lw[:len(lw)-len(rest)] + c
+	}
+	return strings.ToUpper(lw[:1]) + lw[1:]
+}
+
+// initialism writes lw canonical when it is one, also with a plural "s" or trailing digits.
+func (n *Namer) initialism(lw string) (string, bool) {
+	if c, ok := n.initialisms[lw]; ok {
+		return c, true
+	}
+
 	letters := strings.TrimRight(lw, "0123456789")
 	digits := lw[len(letters):]
 	if c, ok := n.initialisms[letters]; ok {
-		return c + digits
+		return c + digits, true
 	}
 	if base, ok := strings.CutSuffix(letters, "s"); ok {
 		if c, found := n.initialisms[base]; found {
-			return c + "s" + digits
+			return c + "s" + digits, true
 		}
 	}
-	return strings.ToUpper(lw[:1]) + lw[1:]
+	return "", false
 }

internal/naming/namer_test.go

@@ -75,6 +75,8 @@ func TestExported(t *testing.T) {
 		{name: "Leading digits before capitals", parts: []string{"2FA"}, want: "N2Fa"},
 		{name: "Leading digits before camel case", parts: []string{"404NotFound"}, want: "N404NotFound"},
 		{name: "Leading digit after a separator", parts: []string{"_3d"}, want: "N3d"},
+		{name: "Initialism after leading digits", parts: []string{"short_2url"}, want: "Short2URL"},
+		{name: "Plural initialism after leading digits", parts: []string{"3ids"}, want: "N3IDs"},
 		{name: "Decimal point between digits", parts: []string{"1.5"}, want: "N1Dot5"},
 		{name: "Version number", parts: []string{"v1.2.3"}, want: "V1Dot2Dot3"},
 		{name: "Dot after a letter is a separator", parts: []string{"a.1"}, want: "A1"},
@@ -134,6 +136,8 @@ func TestExportedWithExtraInitialisms(t *testing.T) {
 		{name: "Extra initialism", extra: []string{"PSP"}, in: "pspId", want: "PSPID"},
 		{name: "Extra initialism given in lower case is written upper case", extra: []string{"ssn"}, in: "SSN", want: "SSN"},
 		{name: "Extra initialism plural", extra: []string{"PSP"}, in: "PSPs", want: "PSPs"},
+		{name: "Extra initialism after leading digits", extra: []string{"DS"}, in: "force_3ds_flow", want: "Force3DSFlow"},
+		{name: "Extra initialism that starts with a digit", extra: []string{"3DS"}, in: "3ds", want: "N3DS"},
 		{name: "Empty extra is ignored", extra: []string{""}, in: "s", want: "S"},
 		{name: "Defaults stay with extras", extra: []string{"PSP"}, in: "url", want: "URL"},
 	}