From d49e44026d73f305b81f9ae77c8a03f8c3d7dfae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20N=C3=A9grier?= <d.negrier@thecodingmachine.com>
Date: Tue, 26 Nov 2024 16:33:40 +0100
Subject: [PATCH] Generating "else if" where applicable

In oneof scenarios, this commit proposes generating "else if" statements where applicable.

The original idea was an attempt to speed up Typescript compilation by reducing the amount of paths Typescript can analyze.
Spoiler alert => nothing changes from that point of view.

Still, the "else if" conditions should slightly speed up the runtime execution,
by avoiding unnecessary checks to the Javascript runtime.
---
 .../google/protobuf/struct.ts                 | 30 ++++-------
 .../google/protobuf/struct.ts                 | 36 ++++++-------
 integration/oneof-unions-value/oneof.ts       | 54 +++++++++----------
 .../oneof-unions/google/protobuf/struct.ts    | 34 +++++-------
 integration/oneof-unions/oneof.ts             | 48 +++++++----------
 .../google/protobuf/struct.ts                 | 34 +++++-------
 .../use-readonly-types/use-readonly-types.ts  |  6 +--
 src/main.ts                                   | 12 ++++-
 8 files changed, 112 insertions(+), 142 deletions(-)

diff --git a/integration/oneof-unions-snake/google/protobuf/struct.ts b/integration/oneof-unions-snake/google/protobuf/struct.ts
index c37458bb6..6e2f28c4e 100644
--- a/integration/oneof-unions-snake/google/protobuf/struct.ts
+++ b/integration/oneof-unions-snake/google/protobuf/struct.ts
@@ -401,20 +401,15 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const obj: any = {};
     if (message.kind?.$case === "null_value") {
       obj.null_value = nullValueToJSON(message.kind.null_value);
-    }
-    if (message.kind?.$case === "number_value") {
+    } else if (message.kind?.$case === "number_value") {
       obj.number_value = message.kind.number_value;
-    }
-    if (message.kind?.$case === "string_value") {
+    } else if (message.kind?.$case === "string_value") {
       obj.string_value = message.kind.string_value;
-    }
-    if (message.kind?.$case === "bool_value") {
+    } else if (message.kind?.$case === "bool_value") {
       obj.bool_value = message.kind.bool_value;
-    }
-    if (message.kind?.$case === "struct_value") {
+    } else if (message.kind?.$case === "struct_value") {
       obj.struct_value = message.kind.struct_value;
-    }
-    if (message.kind?.$case === "list_value") {
+    } else if (message.kind?.$case === "list_value") {
       obj.list_value = message.kind.list_value;
     }
     return obj;
@@ -429,34 +424,29 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
       object.kind?.$case === "null_value" && object.kind?.null_value !== undefined && object.kind?.null_value !== null
     ) {
       message.kind = { $case: "null_value", null_value: object.kind.null_value };
-    }
-    if (
+    } else if (
       object.kind?.$case === "number_value" &&
       object.kind?.number_value !== undefined &&
       object.kind?.number_value !== null
     ) {
       message.kind = { $case: "number_value", number_value: object.kind.number_value };
-    }
-    if (
+    } else if (
       object.kind?.$case === "string_value" &&
       object.kind?.string_value !== undefined &&
       object.kind?.string_value !== null
     ) {
       message.kind = { $case: "string_value", string_value: object.kind.string_value };
-    }
-    if (
+    } else if (
       object.kind?.$case === "bool_value" && object.kind?.bool_value !== undefined && object.kind?.bool_value !== null
     ) {
       message.kind = { $case: "bool_value", bool_value: object.kind.bool_value };
-    }
-    if (
+    } else if (
       object.kind?.$case === "struct_value" &&
       object.kind?.struct_value !== undefined &&
       object.kind?.struct_value !== null
     ) {
       message.kind = { $case: "struct_value", struct_value: object.kind.struct_value };
-    }
-    if (
+    } else if (
       object.kind?.$case === "list_value" && object.kind?.list_value !== undefined && object.kind?.list_value !== null
     ) {
       message.kind = { $case: "list_value", list_value: object.kind.list_value };
diff --git a/integration/oneof-unions-value/google/protobuf/struct.ts b/integration/oneof-unions-value/google/protobuf/struct.ts
index 5bc88ea6d..602beeb67 100644
--- a/integration/oneof-unions-value/google/protobuf/struct.ts
+++ b/integration/oneof-unions-value/google/protobuf/struct.ts
@@ -398,20 +398,15 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const obj: any = {};
     if (message.kind?.$case === "nullValue") {
       obj.nullValue = nullValueToJSON(message.kind.value);
-    }
-    if (message.kind?.$case === "numberValue") {
+    } else if (message.kind?.$case === "numberValue") {
       obj.numberValue = message.kind.value;
-    }
-    if (message.kind?.$case === "stringValue") {
+    } else if (message.kind?.$case === "stringValue") {
       obj.stringValue = message.kind.value;
-    }
-    if (message.kind?.$case === "boolValue") {
+    } else if (message.kind?.$case === "boolValue") {
       obj.boolValue = message.kind.value;
-    }
-    if (message.kind?.$case === "structValue") {
+    } else if (message.kind?.$case === "structValue") {
       obj.structValue = message.kind.value;
-    }
-    if (message.kind?.$case === "listValue") {
+    } else if (message.kind?.$case === "listValue") {
       obj.listValue = message.kind.value;
     }
     return obj;
@@ -424,20 +419,21 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const message = createBaseValue();
     if (object.kind?.$case === "nullValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
       message.kind = { $case: "nullValue", value: object.kind.value };
-    }
-    if (object.kind?.$case === "numberValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
+    } else if (
+      object.kind?.$case === "numberValue" && object.kind?.value !== undefined && object.kind?.value !== null
+    ) {
       message.kind = { $case: "numberValue", value: object.kind.value };
-    }
-    if (object.kind?.$case === "stringValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
+    } else if (
+      object.kind?.$case === "stringValue" && object.kind?.value !== undefined && object.kind?.value !== null
+    ) {
       message.kind = { $case: "stringValue", value: object.kind.value };
-    }
-    if (object.kind?.$case === "boolValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
+    } else if (object.kind?.$case === "boolValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
       message.kind = { $case: "boolValue", value: object.kind.value };
-    }
-    if (object.kind?.$case === "structValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
+    } else if (
+      object.kind?.$case === "structValue" && object.kind?.value !== undefined && object.kind?.value !== null
+    ) {
       message.kind = { $case: "structValue", value: object.kind.value };
-    }
-    if (object.kind?.$case === "listValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
+    } else if (object.kind?.$case === "listValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
       message.kind = { $case: "listValue", value: object.kind.value };
     }
     return message;
diff --git a/integration/oneof-unions-value/oneof.ts b/integration/oneof-unions-value/oneof.ts
index 024a74157..439063cb4 100644
--- a/integration/oneof-unions-value/oneof.ts
+++ b/integration/oneof-unions-value/oneof.ts
@@ -302,20 +302,15 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
     }
     if (message.choice?.$case === "aNumber") {
       obj.aNumber = message.choice.value;
-    }
-    if (message.choice?.$case === "aString") {
+    } else if (message.choice?.$case === "aString") {
       obj.aString = message.choice.value;
-    }
-    if (message.choice?.$case === "aMessage") {
+    } else if (message.choice?.$case === "aMessage") {
       obj.aMessage = PleaseChoose_Submessage.toJSON(message.choice.value);
-    }
-    if (message.choice?.$case === "aBool") {
+    } else if (message.choice?.$case === "aBool") {
       obj.aBool = message.choice.value;
-    }
-    if (message.choice?.$case === "bunchaBytes") {
+    } else if (message.choice?.$case === "bunchaBytes") {
       obj.bunchaBytes = base64FromBytes(message.choice.value);
-    }
-    if (message.choice?.$case === "anEnum") {
+    } else if (message.choice?.$case === "anEnum") {
       obj.anEnum = pleaseChoose_StateEnumToJSON(message.choice.value);
     }
     if (message.age !== 0) {
@@ -323,11 +318,9 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
     }
     if (message.eitherOr?.$case === "either") {
       obj.either = message.eitherOr.value;
-    }
-    if (message.eitherOr?.$case === "or") {
+    } else if (message.eitherOr?.$case === "or") {
       obj.or = message.eitherOr.value;
-    }
-    if (message.eitherOr?.$case === "thirdOption") {
+    } else if (message.eitherOr?.$case === "thirdOption") {
       obj.thirdOption = message.eitherOr.value;
     }
     if (message.signature.length !== 0) {
@@ -347,20 +340,25 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
     message.name = object.name ?? "";
     if (object.choice?.$case === "aNumber" && object.choice?.value !== undefined && object.choice?.value !== null) {
       message.choice = { $case: "aNumber", value: object.choice.value };
-    }
-    if (object.choice?.$case === "aString" && object.choice?.value !== undefined && object.choice?.value !== null) {
+    } else if (
+      object.choice?.$case === "aString" && object.choice?.value !== undefined && object.choice?.value !== null
+    ) {
       message.choice = { $case: "aString", value: object.choice.value };
-    }
-    if (object.choice?.$case === "aMessage" && object.choice?.value !== undefined && object.choice?.value !== null) {
+    } else if (
+      object.choice?.$case === "aMessage" && object.choice?.value !== undefined && object.choice?.value !== null
+    ) {
       message.choice = { $case: "aMessage", value: PleaseChoose_Submessage.fromPartial(object.choice.value) };
-    }
-    if (object.choice?.$case === "aBool" && object.choice?.value !== undefined && object.choice?.value !== null) {
+    } else if (
+      object.choice?.$case === "aBool" && object.choice?.value !== undefined && object.choice?.value !== null
+    ) {
       message.choice = { $case: "aBool", value: object.choice.value };
-    }
-    if (object.choice?.$case === "bunchaBytes" && object.choice?.value !== undefined && object.choice?.value !== null) {
+    } else if (
+      object.choice?.$case === "bunchaBytes" && object.choice?.value !== undefined && object.choice?.value !== null
+    ) {
       message.choice = { $case: "bunchaBytes", value: object.choice.value };
-    }
-    if (object.choice?.$case === "anEnum" && object.choice?.value !== undefined && object.choice?.value !== null) {
+    } else if (
+      object.choice?.$case === "anEnum" && object.choice?.value !== undefined && object.choice?.value !== null
+    ) {
       message.choice = { $case: "anEnum", value: object.choice.value };
     }
     message.age = object.age ?? 0;
@@ -368,11 +366,11 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
       object.eitherOr?.$case === "either" && object.eitherOr?.value !== undefined && object.eitherOr?.value !== null
     ) {
       message.eitherOr = { $case: "either", value: object.eitherOr.value };
-    }
-    if (object.eitherOr?.$case === "or" && object.eitherOr?.value !== undefined && object.eitherOr?.value !== null) {
+    } else if (
+      object.eitherOr?.$case === "or" && object.eitherOr?.value !== undefined && object.eitherOr?.value !== null
+    ) {
       message.eitherOr = { $case: "or", value: object.eitherOr.value };
-    }
-    if (
+    } else if (
       object.eitherOr?.$case === "thirdOption" &&
       object.eitherOr?.value !== undefined &&
       object.eitherOr?.value !== null
diff --git a/integration/oneof-unions/google/protobuf/struct.ts b/integration/oneof-unions/google/protobuf/struct.ts
index 2516fe90b..66c81b604 100644
--- a/integration/oneof-unions/google/protobuf/struct.ts
+++ b/integration/oneof-unions/google/protobuf/struct.ts
@@ -398,20 +398,15 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const obj: any = {};
     if (message.kind?.$case === "nullValue") {
       obj.nullValue = nullValueToJSON(message.kind.nullValue);
-    }
-    if (message.kind?.$case === "numberValue") {
+    } else if (message.kind?.$case === "numberValue") {
       obj.numberValue = message.kind.numberValue;
-    }
-    if (message.kind?.$case === "stringValue") {
+    } else if (message.kind?.$case === "stringValue") {
       obj.stringValue = message.kind.stringValue;
-    }
-    if (message.kind?.$case === "boolValue") {
+    } else if (message.kind?.$case === "boolValue") {
       obj.boolValue = message.kind.boolValue;
-    }
-    if (message.kind?.$case === "structValue") {
+    } else if (message.kind?.$case === "structValue") {
       obj.structValue = message.kind.structValue;
-    }
-    if (message.kind?.$case === "listValue") {
+    } else if (message.kind?.$case === "listValue") {
       obj.listValue = message.kind.listValue;
     }
     return obj;
@@ -424,32 +419,31 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const message = createBaseValue();
     if (object.kind?.$case === "nullValue" && object.kind?.nullValue !== undefined && object.kind?.nullValue !== null) {
       message.kind = { $case: "nullValue", nullValue: object.kind.nullValue };
-    }
-    if (
+    } else if (
       object.kind?.$case === "numberValue" &&
       object.kind?.numberValue !== undefined &&
       object.kind?.numberValue !== null
     ) {
       message.kind = { $case: "numberValue", numberValue: object.kind.numberValue };
-    }
-    if (
+    } else if (
       object.kind?.$case === "stringValue" &&
       object.kind?.stringValue !== undefined &&
       object.kind?.stringValue !== null
     ) {
       message.kind = { $case: "stringValue", stringValue: object.kind.stringValue };
-    }
-    if (object.kind?.$case === "boolValue" && object.kind?.boolValue !== undefined && object.kind?.boolValue !== null) {
+    } else if (
+      object.kind?.$case === "boolValue" && object.kind?.boolValue !== undefined && object.kind?.boolValue !== null
+    ) {
       message.kind = { $case: "boolValue", boolValue: object.kind.boolValue };
-    }
-    if (
+    } else if (
       object.kind?.$case === "structValue" &&
       object.kind?.structValue !== undefined &&
       object.kind?.structValue !== null
     ) {
       message.kind = { $case: "structValue", structValue: object.kind.structValue };
-    }
-    if (object.kind?.$case === "listValue" && object.kind?.listValue !== undefined && object.kind?.listValue !== null) {
+    } else if (
+      object.kind?.$case === "listValue" && object.kind?.listValue !== undefined && object.kind?.listValue !== null
+    ) {
       message.kind = { $case: "listValue", listValue: object.kind.listValue };
     }
     return message;
diff --git a/integration/oneof-unions/oneof.ts b/integration/oneof-unions/oneof.ts
index f4416fbf0..8c17b53e3 100644
--- a/integration/oneof-unions/oneof.ts
+++ b/integration/oneof-unions/oneof.ts
@@ -302,20 +302,15 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
     }
     if (message.choice?.$case === "aNumber") {
       obj.aNumber = message.choice.aNumber;
-    }
-    if (message.choice?.$case === "aString") {
+    } else if (message.choice?.$case === "aString") {
       obj.aString = message.choice.aString;
-    }
-    if (message.choice?.$case === "aMessage") {
+    } else if (message.choice?.$case === "aMessage") {
       obj.aMessage = PleaseChoose_Submessage.toJSON(message.choice.aMessage);
-    }
-    if (message.choice?.$case === "aBool") {
+    } else if (message.choice?.$case === "aBool") {
       obj.aBool = message.choice.aBool;
-    }
-    if (message.choice?.$case === "bunchaBytes") {
+    } else if (message.choice?.$case === "bunchaBytes") {
       obj.bunchaBytes = base64FromBytes(message.choice.bunchaBytes);
-    }
-    if (message.choice?.$case === "anEnum") {
+    } else if (message.choice?.$case === "anEnum") {
       obj.anEnum = pleaseChoose_StateEnumToJSON(message.choice.anEnum);
     }
     if (message.age !== 0) {
@@ -323,11 +318,9 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
     }
     if (message.eitherOr?.$case === "either") {
       obj.either = message.eitherOr.either;
-    }
-    if (message.eitherOr?.$case === "or") {
+    } else if (message.eitherOr?.$case === "or") {
       obj.or = message.eitherOr.or;
-    }
-    if (message.eitherOr?.$case === "thirdOption") {
+    } else if (message.eitherOr?.$case === "thirdOption") {
       obj.thirdOption = message.eitherOr.thirdOption;
     }
     if (message.signature.length !== 0) {
@@ -347,26 +340,27 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
     message.name = object.name ?? "";
     if (object.choice?.$case === "aNumber" && object.choice?.aNumber !== undefined && object.choice?.aNumber !== null) {
       message.choice = { $case: "aNumber", aNumber: object.choice.aNumber };
-    }
-    if (object.choice?.$case === "aString" && object.choice?.aString !== undefined && object.choice?.aString !== null) {
+    } else if (
+      object.choice?.$case === "aString" && object.choice?.aString !== undefined && object.choice?.aString !== null
+    ) {
       message.choice = { $case: "aString", aString: object.choice.aString };
-    }
-    if (
+    } else if (
       object.choice?.$case === "aMessage" && object.choice?.aMessage !== undefined && object.choice?.aMessage !== null
     ) {
       message.choice = { $case: "aMessage", aMessage: PleaseChoose_Submessage.fromPartial(object.choice.aMessage) };
-    }
-    if (object.choice?.$case === "aBool" && object.choice?.aBool !== undefined && object.choice?.aBool !== null) {
+    } else if (
+      object.choice?.$case === "aBool" && object.choice?.aBool !== undefined && object.choice?.aBool !== null
+    ) {
       message.choice = { $case: "aBool", aBool: object.choice.aBool };
-    }
-    if (
+    } else if (
       object.choice?.$case === "bunchaBytes" &&
       object.choice?.bunchaBytes !== undefined &&
       object.choice?.bunchaBytes !== null
     ) {
       message.choice = { $case: "bunchaBytes", bunchaBytes: object.choice.bunchaBytes };
-    }
-    if (object.choice?.$case === "anEnum" && object.choice?.anEnum !== undefined && object.choice?.anEnum !== null) {
+    } else if (
+      object.choice?.$case === "anEnum" && object.choice?.anEnum !== undefined && object.choice?.anEnum !== null
+    ) {
       message.choice = { $case: "anEnum", anEnum: object.choice.anEnum };
     }
     message.age = object.age ?? 0;
@@ -374,11 +368,9 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
       object.eitherOr?.$case === "either" && object.eitherOr?.either !== undefined && object.eitherOr?.either !== null
     ) {
       message.eitherOr = { $case: "either", either: object.eitherOr.either };
-    }
-    if (object.eitherOr?.$case === "or" && object.eitherOr?.or !== undefined && object.eitherOr?.or !== null) {
+    } else if (object.eitherOr?.$case === "or" && object.eitherOr?.or !== undefined && object.eitherOr?.or !== null) {
       message.eitherOr = { $case: "or", or: object.eitherOr.or };
-    }
-    if (
+    } else if (
       object.eitherOr?.$case === "thirdOption" &&
       object.eitherOr?.thirdOption !== undefined &&
       object.eitherOr?.thirdOption !== null
diff --git a/integration/use-readonly-types/google/protobuf/struct.ts b/integration/use-readonly-types/google/protobuf/struct.ts
index 325e08200..a3c773bf5 100644
--- a/integration/use-readonly-types/google/protobuf/struct.ts
+++ b/integration/use-readonly-types/google/protobuf/struct.ts
@@ -398,20 +398,15 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const obj: any = {};
     if (message.kind?.$case === "nullValue") {
       obj.nullValue = nullValueToJSON(message.kind.nullValue);
-    }
-    if (message.kind?.$case === "numberValue") {
+    } else if (message.kind?.$case === "numberValue") {
       obj.numberValue = message.kind.numberValue;
-    }
-    if (message.kind?.$case === "stringValue") {
+    } else if (message.kind?.$case === "stringValue") {
       obj.stringValue = message.kind.stringValue;
-    }
-    if (message.kind?.$case === "boolValue") {
+    } else if (message.kind?.$case === "boolValue") {
       obj.boolValue = message.kind.boolValue;
-    }
-    if (message.kind?.$case === "structValue") {
+    } else if (message.kind?.$case === "structValue") {
       obj.structValue = message.kind.structValue;
-    }
-    if (message.kind?.$case === "listValue") {
+    } else if (message.kind?.$case === "listValue") {
       obj.listValue = message.kind.listValue;
     }
     return obj;
@@ -424,32 +419,31 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
     const message = createBaseValue() as any;
     if (object.kind?.$case === "nullValue" && object.kind?.nullValue !== undefined && object.kind?.nullValue !== null) {
       message.kind = { $case: "nullValue", nullValue: object.kind.nullValue };
-    }
-    if (
+    } else if (
       object.kind?.$case === "numberValue" &&
       object.kind?.numberValue !== undefined &&
       object.kind?.numberValue !== null
     ) {
       message.kind = { $case: "numberValue", numberValue: object.kind.numberValue };
-    }
-    if (
+    } else if (
       object.kind?.$case === "stringValue" &&
       object.kind?.stringValue !== undefined &&
       object.kind?.stringValue !== null
     ) {
       message.kind = { $case: "stringValue", stringValue: object.kind.stringValue };
-    }
-    if (object.kind?.$case === "boolValue" && object.kind?.boolValue !== undefined && object.kind?.boolValue !== null) {
+    } else if (
+      object.kind?.$case === "boolValue" && object.kind?.boolValue !== undefined && object.kind?.boolValue !== null
+    ) {
       message.kind = { $case: "boolValue", boolValue: object.kind.boolValue };
-    }
-    if (
+    } else if (
       object.kind?.$case === "structValue" &&
       object.kind?.structValue !== undefined &&
       object.kind?.structValue !== null
     ) {
       message.kind = { $case: "structValue", structValue: object.kind.structValue };
-    }
-    if (object.kind?.$case === "listValue" && object.kind?.listValue !== undefined && object.kind?.listValue !== null) {
+    } else if (
+      object.kind?.$case === "listValue" && object.kind?.listValue !== undefined && object.kind?.listValue !== null
+    ) {
       message.kind = { $case: "listValue", listValue: object.kind.listValue };
     }
     return message;
diff --git a/integration/use-readonly-types/use-readonly-types.ts b/integration/use-readonly-types/use-readonly-types.ts
index 85064f680..a88bb5bf8 100644
--- a/integration/use-readonly-types/use-readonly-types.ts
+++ b/integration/use-readonly-types/use-readonly-types.ts
@@ -270,8 +270,7 @@ export const Entity: MessageFns<Entity> = {
     }
     if (message.oneOfValue?.$case === "theStringValue") {
       obj.theStringValue = message.oneOfValue.theStringValue;
-    }
-    if (message.oneOfValue?.$case === "theIntValue") {
+    } else if (message.oneOfValue?.$case === "theIntValue") {
       obj.theIntValue = Math.round(message.oneOfValue.theIntValue);
     }
     return obj;
@@ -300,8 +299,7 @@ export const Entity: MessageFns<Entity> = {
       object.oneOfValue?.theStringValue !== null
     ) {
       message.oneOfValue = { $case: "theStringValue", theStringValue: object.oneOfValue.theStringValue };
-    }
-    if (
+    } else if (
       object.oneOfValue?.$case === "theIntValue" &&
       object.oneOfValue?.theIntValue !== undefined &&
       object.oneOfValue?.theIntValue !== null
diff --git a/src/main.ts b/src/main.ts
index 38ea50845..2c73628af 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2394,6 +2394,8 @@ function generateToJson(
       const obj: any = {};
   `);
 
+  let currentIfTarget = "";
+
   // then add a case for each field
   messageDesc.field.forEach((field) => {
     const fieldName = getFieldName(field, options);
@@ -2525,10 +2527,13 @@ function generateToJson(
         : getPropertyAccessor("message", maybeSnakeToCamel(messageDesc.oneofDecl[field.oneofIndex].name, options));
       const valueName = oneofValueName(fieldName, options);
       chunks.push(code`
-        if (${oneofNameWithMessage}?.$case === '${fieldName}') {
+        ${
+          currentIfTarget === oneofNameWithMessage ? "else " : ""
+        }if (${oneofNameWithMessage}?.$case === '${fieldName}') {
           ${jsonProperty} = ${readSnippet(`${oneofNameWithMessage}.${valueName}`)};
         }
       `);
+      currentIfTarget = oneofNameWithMessage;
     } else {
       let emitDefaultValuesForJson = ctx.options.emitDefaultValues.includes("json-methods");
       const check =
@@ -2587,6 +2592,8 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
 
   chunks.push(code`const message = ${createBase}${maybeAsAny(options)};`);
 
+  let currentIfTarget = "";
+
   // add a check for each incoming field
   messageDesc.field.forEach((field) => {
     const fieldName = getFieldName(field, options);
@@ -2704,7 +2711,7 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
       const valueName = oneofValueName(fieldName, options);
       const v = readSnippet(`${oneofNameWithObject}.${valueName}`);
       chunks.push(code`
-        if (
+        ${currentIfTarget === oneofNameWithObject ? "else " : ""}if (
           ${oneofNameWithObject}?.$case === '${fieldName}'
           && ${oneofNameWithObject}?.${valueName} !== undefined
           && ${oneofNameWithObject}?.${valueName} !== null
@@ -2712,6 +2719,7 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
           ${oneofNameWithMessage} = { $case: '${fieldName}', ${valueName}: ${v} };
         }
       `);
+      currentIfTarget = oneofNameWithObject;
     } else if (readSnippet(`x`).toCodeString([]) == "x") {
       // An optimized case of the else below that works when `readSnippet` returns the plain input
       const fallback = isWithinOneOf(field) || noDefaultValue ? "undefined" : defaultValue(ctx, field);