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1 files changed, 34 insertions, 0 deletions

diff --git a/node_modules/tailwindcss/src/util/validateFormalSyntax.js b/node_modules/tailwindcss/src/util/validateFormalSyntax.js
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+++ b/node_modules/tailwindcss/src/util/validateFormalSyntax.js
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+import { length, percentage } from './dataTypes'
+import { splitAtTopLevelOnly } from './splitAtTopLevelOnly'
+
+/**
+ *
+ * https://developer.mozilla.org/en-US/docs/Web/CSS/background-size#formal_syntax
+ *
+ * background-size =
+ *  <bg-size>#
+ *
+ * <bg-size> =
+ *   [ <length-percentage [0,∞]> | auto ]{1,2}  |
+ *   cover                                      |
+ *   contain
+ *
+ * <length-percentage> =
+ *   <length>      |
+ *   <percentage>
+ *
+ * @param {string} value
+ */
+export function backgroundSize(value) {
+  let keywordValues = ['cover', 'contain']
+  // the <length-percentage> type will probably be a css function
+  // so we have to use `splitAtTopLevelOnly`
+  return splitAtTopLevelOnly(value, ',').every((part) => {
+    let sizes = splitAtTopLevelOnly(part, '_').filter(Boolean)
+    if (sizes.length === 1 && keywordValues.includes(sizes[0])) return true
+
+    if (sizes.length !== 1 && sizes.length !== 2) return false
+
+    return sizes.every((size) => length(size) || percentage(size) || size === 'auto')
+  })
+}