feat: new command keep-aligned (#32)

src/commands/index.ts

@@ -1,5 +1,6 @@
 import { hoistRegExp } from './hoist-regexp'
 import { inlineArrow } from './inline-arrow'
+import { keepAligned } from './keep-aligned'
 import { keepSorted } from './keep-sorted'
 import { keepUnique } from './keep-unique'
 import { noShorthand } from './no-shorthand'
@@ -21,6 +22,7 @@ import { toTernary } from './to-ternary'
 export {
   hoistRegExp,
   inlineArrow,
+  keepAligned,
   keepSorted,
   keepUnique,
   noShorthand,
@@ -43,6 +45,7 @@ export {
 export const builtinCommands = [
   hoistRegExp,
   inlineArrow,
+  keepAligned,
   keepSorted,
   keepUnique,
   noShorthand,

src/commands/keep-aligned.md

@@ -0,0 +1,65 @@
+# `keep-aligned`
+
+Keep specific symbols within a block of code are aligned vertically.
+
+## Triggers
+
+- `/// keep-aligned <symbols>`
+- `// @keep-aligned <symbols>`
+
+## Examples
+
+<!-- eslint-skip -->
+
+```typescript
+// @keep-aligned , , ,
+export const matrix = [
+  1, 0, 0,
+  0.866, -0.5, 0,
+  0.5, 0.866, 42,
+]
+```
+
+Will be converted to:
+
+<!-- eslint-skip -->
+
+```typescript
+// @keep-aligned , , ,
+export const matrix = [
+  1    , 0    , 0 ,
+  0.866, -0.5 , 0 ,
+  0.5  , 0.866, 42,
+]
+```
+
+### Repeat Mode
+
+For the example above where `,` is the only repeating symbol for alignment, `keep-aligned*` could be used instead to indicate a repeating pattern:
+
+<!-- eslint-skip -->
+
+```typescript
+// @keep-aligned* ,
+export const matrix = [
+  1, 0, 0,
+  0.866, -0.5, 0,
+  0.5, 0.866, 42,
+]
+```
+
+Will produce the same result.
+
+> [!TIP]
+> This rule does not work well with other spacing rules, namely `style/no-multi-spaces, style/comma-spacing, antfu/consistent-list-newline` were disabled for the example above to work. Consider adding `/* eslint-disable */` to specific ESLint rules for lines affected by this command.
+>
+> ```typescript
+> /* eslint-disable style/no-multi-spaces, style/comma-spacing, antfu/consistent-list-newline */
+> // @keep-aligned , , ,
+> export const matrix = [
+>   1    , 0    , 0 ,
+>   0.866, -0.5 , 0 ,
+>   0.5  , 0.866, 42,
+> ]
+> /* eslint-enable style/no-multi-spaces, style/comma-spacing, antfu/consistent-list-newline */
+> ```

src/commands/keep-aligned.test.ts

@@ -0,0 +1,86 @@
+import { $, run } from './_test-utils'
+import { keepAligned } from './keep-aligned'
+
+run(
+  keepAligned,
+  {
+    code: $`
+      // @keep-aligned , , ,
+      export const matrix = [
+        1, 0, 0,
+        0.866, -0.5, 0,
+        0.5, 0.866, 42,
+      ]
+    `,
+    output(output) {
+      expect(output).toMatchInlineSnapshot(`
+        "// @keep-aligned , , ,
+        export const matrix = [
+          1    , 0    , 0 ,
+          0.866, -0.5 , 0 ,
+          0.5  , 0.866, 42,
+        ]"
+      `)
+    },
+  },
+  {
+    code: $`
+      // @keep-aligned , , ]
+      export const matrix = [
+        [1, 0, 0],
+        [0.866, -0.5, 0],
+        [0.5, 0.866, 42],
+      ] 
+    `,
+    output(output) {
+      expect(output).toMatchInlineSnapshot(`
+        "// @keep-aligned , , ]
+        export const matrix = [
+          [1    , 0    , 0 ],
+          [0.866, -0.5 , 0 ],
+          [0.5  , 0.866, 42],
+        ] "
+      `)
+    },
+  },
+  {
+    code: $`
+      /// keep-aligned* ,
+      export const matrix = [
+        1, 0, 0, 0.866, 0.5, 0.866, 42,
+        0.866, -0.5, 0, 0.5, 0.121212,
+        0.5, 0.866, 118, 1, 0, 0, 0.866, -0.5, 12,
+      ] 
+    `,
+    output(output) {
+      expect(output).toMatchInlineSnapshot(`
+        "/// keep-aligned* ,
+        export const matrix = [
+          1    , 0    , 0  , 0.866, 0.5     , 0.866, 42   ,
+          0.866, -0.5 , 0  , 0.5  , 0.121212,
+          0.5  , 0.866, 118, 1    , 0       , 0    , 0.866, -0.5, 12,
+        ] "
+      `)
+    },
+  },
+  {
+    code: $`
+      function foo(arr: number[][], i: number, j: number) {
+        // @keep-aligned arr[ ] arr[ ] ][j
+        return arr[i - 1][j - 1] + arr[i - 1][j] + arr[i - 1][j + 1]
+          + arr[i][j - 1] + arr[i][j] + arr[i][j + 1]
+          + arr[i + 1][j - 1] + arr[i + 1][j] + arr[i][j + 1]
+      }
+    `,
+    output(output) {
+      expect(output).toMatchInlineSnapshot(`
+        "function foo(arr: number[][], i: number, j: number) {
+          // @keep-aligned arr[ ] arr[ ] ][j
+          return arr[i - 1][j - 1] + arr[i - 1][j] + arr[i - 1][j + 1]
+            +    arr[i    ][j - 1] + arr[i    ][j] + arr[i    ][j + 1]
+            +    arr[i + 1][j - 1] + arr[i + 1][j] + arr[i    ][j + 1]
+        }"
+      `)
+    },
+  },
+)

src/commands/keep-aligned.ts

@@ -0,0 +1,68 @@
+import type { Command } from '../types'
+
+const reLine = /^[/@:]\s*keep-aligned(?<repeat>\*?)(?<symbols>(\s+\S+)+)$/
+
+export const keepAligned: Command = {
+  name: 'keep-aligned',
+  commentType: 'line',
+  match: comment => comment.value.trim().match(reLine),
+  action(ctx) {
+    // this command applies to any node below
+    const node = ctx.findNodeBelow(() => true)
+    if (!node)
+      return
+
+    const alignmentSymbols = ctx.matches.groups?.symbols?.trim().split(/\s+/)
+    if (!alignmentSymbols)
+      return ctx.reportError('No alignment symbols provided')
+    const repeat = ctx.matches.groups?.repeat
+
+    const nLeadingSpaces = node.range[0] - ctx.comment.range[1] - 1
+    const text = ctx.context.sourceCode.getText(node, nLeadingSpaces)
+    const lines = text.split('\n')
+    const symbolIndices: number[] = []
+
+    const nSymbols = alignmentSymbols.length
+    if (nSymbols === 0)
+      return ctx.reportError('No alignment symbols provided')
+
+    const n = repeat ? Number.MAX_SAFE_INTEGER : nSymbols
+    let lastPos = 0
+    for (let i = 0; i < n && i < 20; i++) {
+      const symbol = alignmentSymbols[i % nSymbols]
+      const maxIndex = lines.reduce((maxIndex, line) =>
+        Math.max(line.indexOf(symbol, lastPos), maxIndex), -1)
+      symbolIndices.push(maxIndex)
+
+      if (maxIndex < 0) {
+        if (!repeat)
+          return ctx.reportError(`Alignment symbol "${symbol}" not found`)
+        else
+          break
+      }
+
+      for (let j = 0; j < lines.length; j++) {
+        const line = lines[j]
+        const index = line.indexOf(symbol, lastPos)
+        if (index < 0)
+          continue
+        if (index !== maxIndex) {
+          const padding = maxIndex - index
+          lines[j] = line.slice(0, index) + ' '.repeat(padding) + line.slice(index)
+        }
+      }
+      lastPos = maxIndex + symbol.length
+    }
+
+    const modifiedText = lines.join('\n')
+    if (text === modifiedText)
+      return
+
+    ctx.report({
+      node,
+      message: 'Keep aligned',
+      removeComment: false,
+      fix: fixer => fixer.replaceText(node, modifiedText.slice(nLeadingSpaces)),
+    })
+  },
+}