Add optimized version for review

src/util/toPath.js

@@ -15,6 +15,95 @@
 export function toPath(path) {
   if (Array.isArray(path)) return path
 
+  let parts = []
+  let inBrackets = false
+  let partStart = 0
+  let partEnd = 0
+
+  for (let i = 0, len = path.length; i <= len; i++) {
+    let prev = path[i - 1]
+    let curr = path[i]
+
+    // Tokens:
+    // [ = lb
+    // ] = rb
+    // . = dot if not in brackets
+    // . = ident if in brackets
+    // everything else = ident
+    let prevIsIdent = inBrackets
+      ? prev !== undefined && prev !== '[' && prev !== ']'
+      : prev !== undefined && prev !== '.' && prev !== '[' && prev !== ']'
+
+    let currIsIdent = inBrackets
+      ? curr !== undefined && curr !== '[' && curr !== ']'
+      : curr !== undefined && curr !== '.' && curr !== '[' && curr !== ']'
+
+    // The only valid transitions are:
+    // start -> dot | lb | ident | end
+    // dot   -> ident
+    // lb    -> rb | ident
+    // rb    -> dot | lb
+    // ident -> dot | rb | ident | end
+    // ident -> lb if not in brackets
+    if (
+      (prev === undefined && curr === ']') ||
+      (prev === '.' && !inBrackets && !currIsIdent) ||
+      (prev === '[' && curr === undefined) ||
+      (prev === '[' && curr === '[') ||
+      (prev === ']' && curr === ']') ||
+      (prev === ']' && currIsIdent) ||
+      (prevIsIdent && curr === '[' && inBrackets)
+    ) {
+      throw new Error(`Invalid path: ${path}\n` + `${' '.repeat(14 + i)}^`)
+    }
+
+    // The last thing we looked at was an ident so we ened to keep looking for more
+    // Later scans will identify the end of the ident
+    if (prevIsIdent) {
+      partEnd = i
+    }
+
+    // Whenever we go from an ident to a non-ident we capture the new part
+    // We also capture:
+    // - start -> dot for initial empty strings
+    // - lb -> rb for ocurrences of [] also treated as empty strings
+    if (
+      (prev === undefined && curr === '.') ||
+      (prev === '[' && curr === ']') ||
+      (prevIsIdent && curr === '.' && !inBrackets) ||
+      (prevIsIdent && curr === '[' && !inBrackets) ||
+      (prevIsIdent && curr === ']') ||
+      (prevIsIdent && curr === undefined)
+    ) {
+      parts.push(path.slice(partStart, partEnd))
+    }
+
+    // Whenever we go from a non-ident to ident we start capturing a new part
+    // We also capture start -> lb for initial empty strings generated by `[]`
+    if (
+      (prev === undefined && curr === '[') ||
+      (prev === '.' && !inBrackets && currIsIdent) ||
+      (prev === '[' && currIsIdent) ||
+      (prev === ']' && curr === '.')
+    ) {
+      partStart = partEnd = i
+    }
+
+    // Bracket bookkeeping
+    if (curr === '[') {
+      inBrackets = true
+    } else if (curr === ']') {
+      inBrackets = false
+    }
+  }
+
+  return parts
+}
+
+// Herre for reference in case one is preferred over the other
+export function toPathFull(path) {
+  if (Array.isArray(path)) return path
+
   // The general outline/properties of a path string:
 
   // Tokens: