Stream split results with SplitSeq and FieldsSeq Has Fix

• Playground Link

Description

Go 1.24 added SplitSeq and FieldsSeq to strings and bytes. When a range loop discards the slice index, these helpers stream each part without first allocating the complete result slice. The rule preserves the loop body and deliberately ignores loops that use the index.

It assumes strings and bytes are the canonical standard-library package names and does not manage imports.

YAML

id: use-split-seq
language: Go
severity: hint
message: Stream split results with a Seq helper.
rule:
  pattern:
    context: |
      func f() {
        for _, $ITEM := range $PACKAGE.$FUNCTION($$$ARGS) {
          $$$BODY
        }
      }
    selector: for_statement
constraints:
  PACKAGE:
    regex: '^(strings|bytes)$'
  FUNCTION:
    regex: '^(Split|Fields)$'
  ITEM:
    all:
      - kind: identifier
      - not:
          regex: '^_$'
transform:
  SEQ_FUNCTION:
    replace:
      source: $FUNCTION
      replace: '$'
      by: Seq
fix: |-
  for $ITEM := range $PACKAGE.$SEQ_FUNCTION($$$ARGS) {
    $$$BODY
  }

Example

import (
  "bytes"
  "strings"
)

func visit(text string, data []byte) {
  for _, part := range strings.Split(text, ",") {
    useString(part)
  }
  for _, field := range bytes.Fields(data) {
    useBytes(field)
  }
}

Diff

import (
  "bytes"
  "strings"
)

func visit(text string, data []byte) {
  for _, part := range strings.Split(text, ",") { 
  for part := range strings.SplitSeq(text, ",") { 
    useString(part)
  }
  for _, field := range bytes.Fields(data) { 
  for field := range bytes.FieldsSeq(data) { 
    useBytes(field)
  }
}

Credits

Based on JetBrains' Go Modern Guidelines.