1 files changed, 93 insertions, 0 deletions
diff --git a/node_modules/tailwindcss/src/lib/collapseDuplicateDeclarations.js b/node_modules/tailwindcss/src/lib/collapseDuplicateDeclarations.js
new file mode 100644
index 0000000..d310d58
--- /dev/null
+++ b/node_modules/tailwindcss/src/lib/collapseDuplicateDeclarations.js
@@ -0,0 +1,93 @@
+export default function collapseDuplicateDeclarations() {
+  return (root) => {
+    root.walkRules((node) => {
+      let seen = new Map()
+      let droppable = new Set([])
+      let byProperty = new Map()
+
+      node.walkDecls((decl) => {
+        // This could happen if we have nested selectors. In that case the
+        // parent will loop over all its declarations but also the declarations
+        // of nested rules. With this we ensure that we are shallowly checking
+        // declarations.
+        if (decl.parent !== node) {
+          return
+        }
+
+        if (seen.has(decl.prop)) {
+          // Exact same value as what we have seen so far
+          if (seen.get(decl.prop).value === decl.value) {
+            // Keep the last one, drop the one we've seen so far
+            droppable.add(seen.get(decl.prop))
+            // Override the existing one with the new value. This is necessary
+            // so that if we happen to have more than one declaration with the
+            // same value, that we keep removing the previous one. Otherwise we
+            // will only remove the *first* one.
+            seen.set(decl.prop, decl)
+            return
+          }
+
+          // Not the same value, so we need to check if we can merge it so
+          // let's collect it first.
+          if (!byProperty.has(decl.prop)) {
+            byProperty.set(decl.prop, new Set())
+          }
+
+          byProperty.get(decl.prop).add(seen.get(decl.prop))
+          byProperty.get(decl.prop).add(decl)
+        }
+
+        seen.set(decl.prop, decl)
+      })
+
+      // Drop all the duplicate declarations with the exact same value we've
+      // already seen so far.
+      for (let decl of droppable) {
+        decl.remove()
+      }
+
+      // Analyze the declarations based on its unit, drop all the declarations
+      // with the same unit but the last one in the list.
+      for (let declarations of byProperty.values()) {
+        let byUnit = new Map()
+
+        for (let decl of declarations) {
+          let unit = resolveUnit(decl.value)
+          if (unit === null) {
+            // We don't have a unit, so should never try and collapse this
+            // value. This is because we can't know how to do it in a correct
+            // way (e.g.: overrides for older browsers)
+            continue
+          }
+
+          if (!byUnit.has(unit)) {
+            byUnit.set(unit, new Set())
+          }
+
+          byUnit.get(unit).add(decl)
+        }
+
+        for (let declarations of byUnit.values()) {
+          // Get all but the last one
+          let removableDeclarations = Array.from(declarations).slice(0, -1)
+
+          for (let decl of removableDeclarations) {
+            decl.remove()
+          }
+        }
+      }
+    })
+  }
+}
+
+let UNITLESS_NUMBER = Symbol('unitless-number')
+
+function resolveUnit(input) {
+  let result = /^-?\d*.?\d+([\w%]+)?$/g.exec(input)
+
+  if (result) {
+    return result[1] ?? UNITLESS_NUMBER
+  }
+
+  return null
+}