feat(linter/unicorn): implement prefer-single-call rule by bkmashiro · Pull Request #22857 · oxc-project/oxc

bkmashiro · 2026-05-30T22:52:07Z

Closes #684 (unicorn/prefer-single-call entry)

Summary

Implements the unicorn/prefer-single-call lint rule, which supersedes the deprecated unicorn/no-array-push-push.

Detects consecutive calls to the same variadic method on the same receiver and suggests merging them into a single call
Covers Array#push(), Element#classList.add(), Element#classList.remove(), and importScripts()
Provides an auto-fix that merges arguments, handles trailing commas, and preserves semicolons for ASI safety
Skips ignored push receivers (this.push, stream.push, process.stdin/stdout/stderr.push, this.stream.push)
Only merges when the receiver is a stable expression (identifier, this, or static member chain — not a function call result)

Test plan

Pass cases: different methods, different receivers, non-consecutive calls, optional chains, ignored patterns, unstable receivers, computed members
Fail/fix cases: basic push, multi-arg, trailing comma, ASI no-semi, spread args, classList.add/remove, importScripts, function body, nested member, this.prop.push, three consecutive calls
cargo test -p oxc_linter -- prefer_single_call passes

Copilot

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds the unicorn/prefer-single-call lint rule with auto-fixes to merge consecutive variadic calls (e.g., push, classList.add/remove, importScripts) into a single call.

Changes:

Introduces PreferSingleCall rule implementation with diagnostics + fix merging consecutive calls.
Adds unit tests and a snapshot covering common and edge cases (ASI, trailing commas, spread args, nesting).
Wires the rule into the unicorn module plus generated enums/runners for registration.

Reviewed changes

Copilot reviewed 3 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/oxc_linter/src/rules/unicorn/prefer_single_call.rs	New rule implementation, fix logic, and tests for merging consecutive calls
crates/oxc_linter/src/snapshots/unicorn_prefer_single_call.snap	Snapshot output for the new rule’s diagnostics
crates/oxc_linter/src/rules.rs	Exposes the new unicorn rule module
crates/oxc_linter/src/generated/rules_enum.rs	Registers the new rule in the generated rule enum and metadata
crates/oxc_linter/src/generated/rule_runner_impls.rs	Adds RuleRunner implementation for the new rule

+        // Locate the previous sibling statement in the parent block.
+        let parent = ctx.nodes().parent_node(node.id());
+        let stmts: &[Statement<'a>] = match parent.kind() {
+            AstKind::BlockStatement(b) => &b.body,
+            AstKind::Program(p) => &p.body,
+            AstKind::FunctionBody(b) => &b.statements,
+            AstKind::StaticBlock(b) => &b.body,
+            AstKind::SwitchCase(c) => &c.consequent,
+            _ => return,
+        };
+
+        let Some(idx) = stmts.iter().position(|s| s.span() == expr_stmt.span) else {
+            return;
+        };


+                    if !is_stable_receiver(&member.object) {
+                        return None;
+                    }
+                    let callee_text = call.callee.span().source_text(src);
+                    if PUSH_IGNORE.contains(&callee_text) {
+                        return None;
+                    }
+                    let receiver_text = member.object.span().source_text(src);
+                    Some(CallInfo {
+                        description: "Array#push()",
+                        receiver_text,
+                        diagnostic_span: member.property.span,
+                    })


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chatgpt-codex-connector · 2026-05-30T22:54:31Z

+                let args_text = second_args
+                    .iter()
+                    .map(|a| a.span().source_text(src))
+                    .collect::<Vec<_>>()
+                    .join(", ");


Do not autofix state-dependent second arguments

When the second call's arguments read state changed by the first call, this autofix moves that evaluation before the first call executes. For example, arr.push(1); arr.push(arr.length); pushes the updated length in the original code, but the fix produces arr.push(1, arr.length);, where arr.length is evaluated before 1 is pushed. The rule should avoid offering a fix (or avoid reporting) unless the later arguments are proven independent of the first call's side effects.

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chatgpt-codex-connector · 2026-05-30T22:54:31Z

+            let gap_span = Span::new(first_stmt_end, second_stmt_end);
+            if !first_has_semi && second_has_semi {
+                fix.push(Fix::new(";", gap_span));
+            } else {
+                fix.push(Fix::delete(gap_span));


Preserve comments between merged calls

This deletion span covers all trivia between the end of the first statement and the end of the second statement, so an autofix for foo.push(1); // keep this\nfoo.push(2); silently removes the intervening comment. Fixes should not drop user comments; either preserve comments in the replacement or withhold the fix when the gap contains comments.

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camc314

see comment about performance

camc314 · 2026-06-01T09:16:25Z

+            let Statement::ExpressionStatement(prev_es) = prev_stmt else { continue; };
+            let Statement::ExpressionStatement(curr_es) = curr_stmt else { continue; };


i think it's going to be cheaper (better performance) to instead match only expression stmts, then look at their parents, then siblings.

This code effectivly manually iterates over every single stmt in the program which will be slow, I think doing it the other way round should be cheaper

camc314 · 2026-06-10T13:37:48Z

@bkmashiro i seem to have screwed up a rebase - do you mind making a new PR with a branch name different to main ? 😅

codspeed-hq · 2026-06-10T13:37:51Z

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 61 skipped benchmarks¹

_{Comparing bkmashiro:main (282f41a) with main (0f200a9)}

61 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

bkmashiro · 2026-06-10T13:56:45Z

No worries! Opened a new PR from a non-main branch here: #23235

Closes #684 (unicorn/prefer-single-call entry) Supersedes #22857 (reopened from a non-`main` branch after the old PR branch got rebased incorrectly). ## Summary Implements the `unicorn/prefer-single-call` lint rule, which supersedes the deprecated `unicorn/no-array-push-push`. - Detects consecutive calls to the same variadic method on the same receiver and suggests merging them into a single call - Covers `Array#push()`, `Element#classList.add()`, `Element#classList.remove()`, and `importScripts()` - Provides an auto-fix that merges arguments, handles trailing commas, and preserves semicolons for ASI handling - Skips ignored `push` receivers (`this.push`, `stream.push`, `process.stdin/stdout/stderr.push`, `this.stream.push`) - Only merges when the receiver is a stable expression (identifier, `this`, or static member chain — not a function call result) - Addresses prior review feedback by running from `ExpressionStatement` and checking the parent statement list / previous sibling - Updates the website linter schema snapshot and npm oxlint configuration schema for the new rule ## Test plan - [x] Pass cases: different methods, different receivers, non-consecutive calls, optional chains, ignored patterns, unstable receivers, computed members - [x] Fail/fix cases: basic push, multi-arg, trailing comma, ASI no-semi, spread args, classList.add/remove, importScripts, function body, nested member, `this.prop.push`, three consecutive calls - [x] `cargo fmt --check` - [x] `cargo test -p oxc_linter -- prefer_single_call` - [x] `cargo test -p website_linter --bin website_linter json_schema::test_schema_json` - [x] `git diff --check` ## AI usage disclosure I used AI assistance while preparing and iterating on this PR, and I reviewed the generated changes and test results before submission. --------- Co-authored-by: Cameron Clark <cameron.clark@hey.com>

Copilot AI review requested due to automatic review settings May 30, 2026 22:52

bkmashiro requested a review from camc314 as a code owner May 30, 2026 22:52

Copilot AI reviewed May 30, 2026

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chatgpt-codex-connector Bot reviewed May 30, 2026

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camc314 added the A-linter Area - Linter label May 31, 2026

camc314 changed the title ~~feat(linter): implement unicorn/prefer-single-call rule~~ feat(linter/unicorn): implement prefer-single-call rule May 31, 2026

camc314 requested changes Jun 1, 2026

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camc314 closed this Jun 10, 2026

camc314 force-pushed the main branch from 282f41a to dd1b927 Compare June 10, 2026 13:35

camc314 self-assigned this Jun 10, 2026

bkmashiro mentioned this pull request Jun 10, 2026

feat(linter/unicorn): implement prefer-single-call rule #23235

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feat(linter/unicorn): implement prefer-single-call rule#22857

feat(linter/unicorn): implement prefer-single-call rule#22857
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bkmashiro commented May 30, 2026 •

edited

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		let Statement::ExpressionStatement(prev_es) = prev_stmt else { continue; };
		let Statement::ExpressionStatement(curr_es) = curr_stmt else { continue; };

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Merging this PR will not alter performance

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bkmashiro commented May 30, 2026 •

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