Use nullish coalescing operator (??) for assigning binaries

[webmaster128]

We generate a lot of code like this:

  fromPartial(object: DeepPartial<ExistenceProof>): ExistenceProof {
    const message = { ...baseExistenceProof } as ExistenceProof;
    message.path = [];
    if (object.key !== undefined && object.key !== null) {
      message.key = object.key;
    } else {
      message.key = new Uint8Array();
    }
    if (object.value !== undefined && object.value !== null) {
      message.value = object.value;
    } else {
      message.value = new Uint8Array();
    }
    if (object.leaf !== undefined && object.leaf !== null) {
      message.leaf = LeafOp.fromPartial(object.leaf);
    } else {
      message.leaf = undefined;
    }
    if (object.path !== undefined && object.path !== null) {
      for (const e of object.path) {
        message.path.push(InnerOp.fromPartial(e));
      }
    }
    return message;
  },

in which the binary fields can be replaced with the nullish coalescing operator (??) as follows:

@@ -429,16 +429,8 @@ export const ExistenceProof = {
   fromPartial(object: DeepPartial<ExistenceProof>): ExistenceProof {
     const message = { ...baseExistenceProof } as ExistenceProof;
     message.path = [];
-    if (object.key !== undefined && object.key !== null) {
-      message.key = object.key;
-    } else {
-      message.key = new Uint8Array();
-    }
-    if (object.value !== undefined && object.value !== null) {
-      message.value = object.value;
-    } else {
-      message.value = new Uint8Array();
-    }
+    message.key = object.key ?? new Uint8Array();
+    message.value = object.value ?? new Uint8Array();
     if (object.leaf !== undefined && object.leaf !== null) {
       message.leaf = LeafOp.fromPartial(object.leaf);
     } else {

This output is easier to read and saves a good amount of code size that is otherwise shipped to the user.

Nullish Coalescing is available since TypeScript 3.7 and will be transpiled to a compact replacement. For targets >= es2020 it will be preserved as valid JavaScript syntax. See also JavaScript operator: Nullish coalescing operator on caniuse.com.

In order to make such a change, a bit of refactoring is needed. Instead of have a separate block for the default initializations, each field should be fully initialized in one step, either with data or with default. But such a refactoring would be nice anyways as it makes the flow easier and future optimizations possible, like this one:

@@ -439,11 +439,9 @@ export const ExistenceProof = {
     } else {
       message.value = new Uint8Array();
     }
-    if (object.leaf !== undefined && object.leaf !== null) {
-      message.leaf = LeafOp.fromPartial(object.leaf);
-    } else {
-      message.leaf = undefined;
-    }
+    message.leaf = (object.leaf !== undefined && object.leaf !== null)
+      ? LeafOp.fromPartial(object.leaf)
+      : undefined;
     if (object.path !== undefined && object.path !== null) {
       for (const e of object.path) {
         message.path.push(InnerOp.fromPartial(e));

I'm happy to work on this if there is general interest on the approach.

[stephenh]

Hey @webmaster128 , I think this change would be pretty great; and PRs for it would be even better! :-D Thanks!

[stephenh]

🎉 This issue has been resolved in version 1.84.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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