Prefer splitting right hand side of assignment statements.

[yilei]

Description

When an assignment statement's left hand side fits on a single line, prefer splitting the right hand side's outer optional parens.

Fixes #1498.

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[github-actions]

diff-shades results comparing this PR (bcc8075) to main (a282181). The full diff is available in the logs under the "Generate HTML diff report" step.

╭──────────────────────── Summary ─────────────────────────╮
│ 11 projects & 66 files changed / 750 changes [+376/-374] │
│                                                          │
│ ... out of 2 355 274 lines, 10 989 files & 23 projects   │
╰──────────────────────────────────────────────────────────╯

Differences found.

What is this? | Workflow run | diff-shades documentation

[yilei]

Looking at the diff-shades results, I need to fix the following isuses:

1. Trailing comma in a RHS tuple isn't handled:

-        (
-            field,
-            targets,
-            alias,
-            joins,
-            path,
-            opts,
-            transform_function,
-        ) = self._setup_joins(pieces, opts, alias)
+        (field, targets, alias, joins, path, opts, transform_function,) = (
+            self._setup_joins(pieces, opts, alias)
+        )

2. There are some unrelated changes where the RHS of an assignment statement has un-nested pairs of inner parens, example:

             clone.external_aliases[alias] = (
-                isinstance(table, Join)
-                and table.join_field.related_model._meta.db_table != alias
-            ) or (
-                isinstance(table, BaseTable) and table.table_name != table.table_alias
+                (
+                    isinstance(table, Join)
+                    and table.join_field.related_model._meta.db_table != alias
+                )
+                or (
+                    isinstance(table, BaseTable)
+                    and table.table_name != table.table_alias
+                )
             )

3. This is bad:

         y_hat_discrete[
             np.arange(y_hat_probas.shape[0]), y_hat_probas.argmax(axis=1)
-        ] = 1
+        ] = (1)

[JelleZijlstra]

I was going to point out 1. but you beat me :)

I don't think 2. is a problem: the parentheses around each and are preserved, it just adds new parentheses around the whole RHS.

[JelleZijlstra]

I noticed this one:

-    df["category"] = Series(
-        np.array(list("abcdefghij")).take(np.random.randint(0, 10, size=n))
-    ).astype("category")
+    df["category"] = (
+        Series(
+            np.array(list("abcdefghij")).take(np.random.randint(0, 10, size=n))
+        ).astype("category")
+    )

which I realize is another example of what you meant by 2.

[JelleZijlstra]

Also wanted to mention that most of the changes in diff-shades are clear improvements. This is going to be a positive change.

[yilei]

Adding a note, looks like the handling of trailing comma on the left side is related to an existing issue:

(
    a,
    b,
    c,
    d,
) = func1(arg1)

(a, b, c, d,) = func1(
    arg1
) and func2(arg2)

playground link

Maybe #1671?

[yilei]

The three issues mentioned above are now fixed, this is ready to review again.

[yilei]

Kindly ping? @JelleZijlstra

[JelleZijlstra]

Looked over diff-shades again and everything looks good.