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Properly skip over nodes when using replaceNode (#16300)
Fixes #16298 This PR fixes an issue where using an AST walk in combination with `replaceNode` and various `SkipAction` would either cause children to be visited multiple times or not visited at all even though it should. This PR fixes the issue which also means we can get rid of a custom walk for `@variant` inside the `@media` that was used to apply `@variant` because we never recursively visited children inside the `@media` rule. Because we now can use the regular walk for `@variant`, we now properly convert `@variant` to `@custom-variant` inside `@reference`-ed stylesheet which also fixes #16298 ## Test plan Lots of tests added to ensure the combinations of `WalkAction` and `replaceWith()` works as expected.
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‎CHANGELOG.md‎

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@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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- Fix support for older instruction sets on Linux x64 builds of the standalone CLI ([#16244](https://github.com/tailwindlabs/tailwindcss/pull/16244))
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- Ensure `NODE_PATH` is respected when resolving JavaScript and CSS files ([#16274](https://github.com/tailwindlabs/tailwindcss/pull/16274))
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- Ensure Node addons are packaged correctly with FreeBSD builds ([#16277](https://github.com/tailwindlabs/tailwindcss/pull/16277))
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- Fix an issue where `@variant` inside a referenced stylesheet could cause a stack overflow ([#16300](https://github.com/tailwindlabs/tailwindcss/pull/16300))
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## [4.0.3] - 2025-02-01
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‎packages/tailwindcss/src/ast.test.ts‎

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@@ -1,5 +1,15 @@
11
import { expect, it } from 'vitest'
2-
import { context, decl, optimizeAst, styleRule, toCss, walk, WalkAction } from './ast'
2+
import {
3+
atRule,
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context,
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decl,
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optimizeAst,
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styleRule,
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toCss,
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walk,
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WalkAction,
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type AstNode,
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} from './ast'
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import * as CSS from './css-parser'
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const css = String.raw
@@ -188,3 +198,310 @@ it('should not emit empty rules once optimized', () => {
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"
189199
`)
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})
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it('should only visit children once when calling `replaceWith` with single element array', () => {
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let visited = new Set()
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let ast = [
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atRule('@media', '', [styleRule('.foo', [decl('color', 'blue')])]),
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styleRule('.bar', [decl('color', 'blue')]),
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]
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walk(ast, (node, { replaceWith }) => {
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if (visited.has(node)) {
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throw new Error('Visited node twice')
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}
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visited.add(node)
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if (node.kind === 'at-rule') replaceWith(node.nodes)
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})
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})
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it('should only visit children once when calling `replaceWith` with multi-element array', () => {
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let visited = new Set()
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let ast = [
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atRule('@media', '', [
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context({}, [
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styleRule('.foo', [decl('color', 'red')]),
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styleRule('.baz', [decl('color', 'blue')]),
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]),
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]),
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styleRule('.bar', [decl('color', 'green')]),
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]
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walk(ast, (node, { replaceWith }) => {
234+
let key = id(node)
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if (visited.has(key)) {
236+
throw new Error('Visited node twice')
237+
}
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visited.add(key)
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if (node.kind === 'at-rule') replaceWith(node.nodes)
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})
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expect(visited).toMatchInlineSnapshot(`
244+
Set {
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"@media ",
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".foo",
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"color: red",
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".baz",
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"color: blue",
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".bar",
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"color: green",
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}
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`)
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})
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it('should never visit children when calling `replaceWith` with `WalkAction.Skip`', () => {
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let visited = new Set()
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let inner = styleRule('.foo', [decl('color', 'blue')])
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let ast = [atRule('@media', '', [inner]), styleRule('.bar', [decl('color', 'blue')])]
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walk(ast, (node, { replaceWith }) => {
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visited.add(node)
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if (node.kind === 'at-rule') {
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replaceWith(node.nodes)
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return WalkAction.Skip
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}
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})
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expect(visited).not.toContain(inner)
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expect(visited).toMatchInlineSnapshot(`
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Set {
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{
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"kind": "at-rule",
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"name": "@media",
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"nodes": [
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{
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"kind": "rule",
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"nodes": [
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{
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"important": false,
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"kind": "declaration",
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"property": "color",
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"value": "blue",
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},
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],
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"selector": ".foo",
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},
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],
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"params": "",
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},
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{
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"kind": "rule",
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"nodes": [
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{
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"important": false,
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"kind": "declaration",
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"property": "color",
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"value": "blue",
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},
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],
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"selector": ".bar",
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},
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{
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"important": false,
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"kind": "declaration",
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"property": "color",
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"value": "blue",
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},
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}
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`)
314+
})
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316+
it('should skip the correct number of children based on the the replaced children nodes', () => {
317+
{
318+
let ast = [
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decl('--index', '0'),
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decl('--index', '1'),
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decl('--index', '2'),
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decl('--index', '3'),
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decl('--index', '4'),
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]
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let visited: string[] = []
326+
walk(ast, (node, { replaceWith }) => {
327+
visited.push(id(node))
328+
if (node.kind === 'declaration' && node.value === '2') {
329+
replaceWith([])
330+
return WalkAction.Skip
331+
}
332+
})
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334+
expect(visited).toMatchInlineSnapshot(`
335+
[
336+
"--index: 0",
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"--index: 1",
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"--index: 2",
339+
"--index: 3",
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"--index: 4",
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]
342+
`)
343+
}
344+
345+
{
346+
let ast = [
347+
decl('--index', '0'),
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decl('--index', '1'),
349+
decl('--index', '2'),
350+
decl('--index', '3'),
351+
decl('--index', '4'),
352+
]
353+
let visited: string[] = []
354+
walk(ast, (node, { replaceWith }) => {
355+
visited.push(id(node))
356+
if (node.kind === 'declaration' && node.value === '2') {
357+
replaceWith([])
358+
return WalkAction.Continue
359+
}
360+
})
361+
362+
expect(visited).toMatchInlineSnapshot(`
363+
[
364+
"--index: 0",
365+
"--index: 1",
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"--index: 2",
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"--index: 3",
368+
"--index: 4",
369+
]
370+
`)
371+
}
372+
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{
374+
let ast = [
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decl('--index', '0'),
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decl('--index', '1'),
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decl('--index', '2'),
378+
decl('--index', '3'),
379+
decl('--index', '4'),
380+
]
381+
let visited: string[] = []
382+
walk(ast, (node, { replaceWith }) => {
383+
visited.push(id(node))
384+
if (node.kind === 'declaration' && node.value === '2') {
385+
replaceWith([decl('--index', '2.1')])
386+
return WalkAction.Skip
387+
}
388+
})
389+
390+
expect(visited).toMatchInlineSnapshot(`
391+
[
392+
"--index: 0",
393+
"--index: 1",
394+
"--index: 2",
395+
"--index: 3",
396+
"--index: 4",
397+
]
398+
`)
399+
}
400+
401+
{
402+
let ast = [
403+
decl('--index', '0'),
404+
decl('--index', '1'),
405+
decl('--index', '2'),
406+
decl('--index', '3'),
407+
decl('--index', '4'),
408+
]
409+
let visited: string[] = []
410+
walk(ast, (node, { replaceWith }) => {
411+
visited.push(id(node))
412+
if (node.kind === 'declaration' && node.value === '2') {
413+
replaceWith([decl('--index', '2.1')])
414+
return WalkAction.Continue
415+
}
416+
})
417+
418+
expect(visited).toMatchInlineSnapshot(`
419+
[
420+
"--index: 0",
421+
"--index: 1",
422+
"--index: 2",
423+
"--index: 2.1",
424+
"--index: 3",
425+
"--index: 4",
426+
]
427+
`)
428+
}
429+
430+
{
431+
let ast = [
432+
decl('--index', '0'),
433+
decl('--index', '1'),
434+
decl('--index', '2'),
435+
decl('--index', '3'),
436+
decl('--index', '4'),
437+
]
438+
let visited: string[] = []
439+
walk(ast, (node, { replaceWith }) => {
440+
visited.push(id(node))
441+
if (node.kind === 'declaration' && node.value === '2') {
442+
replaceWith([decl('--index', '2.1'), decl('--index', '2.2')])
443+
return WalkAction.Skip
444+
}
445+
})
446+
447+
expect(visited).toMatchInlineSnapshot(`
448+
[
449+
"--index: 0",
450+
"--index: 1",
451+
"--index: 2",
452+
"--index: 3",
453+
"--index: 4",
454+
]
455+
`)
456+
}
457+
458+
{
459+
let ast = [
460+
decl('--index', '0'),
461+
decl('--index', '1'),
462+
decl('--index', '2'),
463+
decl('--index', '3'),
464+
decl('--index', '4'),
465+
]
466+
let visited: string[] = []
467+
walk(ast, (node, { replaceWith }) => {
468+
visited.push(id(node))
469+
if (node.kind === 'declaration' && node.value === '2') {
470+
replaceWith([decl('--index', '2.1'), decl('--index', '2.2')])
471+
return WalkAction.Continue
472+
}
473+
})
474+
475+
expect(visited).toMatchInlineSnapshot(`
476+
[
477+
"--index: 0",
478+
"--index: 1",
479+
"--index: 2",
480+
"--index: 2.1",
481+
"--index: 2.2",
482+
"--index: 3",
483+
"--index: 4",
484+
]
485+
`)
486+
}
487+
})
488+
489+
function id(node: AstNode) {
490+
switch (node.kind) {
491+
case 'at-rule':
492+
return `${node.name} ${node.params}`
493+
case 'rule':
494+
return node.selector
495+
case 'context':
496+
return '<context>'
497+
case 'at-root':
498+
return '<at-root>'
499+
case 'declaration':
500+
return `${node.property}: ${node.value}`
501+
case 'comment':
502+
return `// ${node.value}`
503+
default:
504+
node satisfies never
505+
throw new Error('Unknown node kind')
506+
}
507+
}

‎packages/tailwindcss/src/ast.ts‎

Lines changed: 21 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -137,39 +137,54 @@ export function walk(
137137
}
138138

139139
path.push(node)
140+
let replacedNode = false
141+
let replacedNodeOffset = 0
140142
let status =
141143
visit(node, {
142144
parent,
143145
context,
144146
path,
145147
replaceWith(newNode) {
148+
replacedNode = true
149+
146150
if (Array.isArray(newNode)) {
147151
if (newNode.length === 0) {
148152
ast.splice(i, 1)
153+
replacedNodeOffset = 0
149154
} else if (newNode.length === 1) {
150155
ast[i] = newNode[0]
156+
replacedNodeOffset = 1
151157
} else {
152158
ast.splice(i, 1, ...newNode)
159+
replacedNodeOffset = newNode.length
153160
}
154161
} else {
155162
ast[i] = newNode
163+
replacedNodeOffset = 1
156164
}
157-
158-
// We want to visit the newly replaced node(s), which start at the
159-
// current index (i). By decrementing the index here, the next loop
160-
// will process this position (containing the replaced node) again.
161-
i--
162165
},
163166
}) ?? WalkAction.Continue
164167
path.pop()
165168

169+
// We want to visit or skip the newly replaced node(s), which start at the
170+
// current index (i). By decrementing the index here, the next loop will
171+
// process this position (containing the replaced node) again.
172+
if (replacedNode) {
173+
if (status === WalkAction.Continue) {
174+
i--
175+
} else {
176+
i += replacedNodeOffset - 1
177+
}
178+
continue
179+
}
180+
166181
// Stop the walk entirely
167182
if (status === WalkAction.Stop) return WalkAction.Stop
168183

169184
// Skip visiting the children of this node
170185
if (status === WalkAction.Skip) continue
171186

172-
if (node.kind === 'rule' || node.kind === 'at-rule') {
187+
if ('nodes' in node) {
173188
path.push(node)
174189
let result = walk(node.nodes, visit, path, context)
175190
path.pop()

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