Function parseDotEnvContents

repos/effect/packages/effect/src/ConfigProvider.ts:943–976

(lines: string)

function buildEnvTrie(env: Record<string, string | undefined>): EnvTrieNode {
  const trie: EnvTrieNode = {}

  for (const [name, value] of Object.entries(env)) {
    if (value === undefined) continue

    // Split on "_" and keep empty segments (no special handling for "__")
    const segments = name.split("_")

    let node = trie
    for (const seg of segments) {
      const children = node.children ??= Object.create(null)
      node = children[seg] ??= {}
    }
  }

  return trie
}

const NUMERIC_INDEX = /^(0|[1-9][0-9]*)$/

function nodeAtEnv(
  trie: EnvTrieNode,
  env: Record<string, string | undefined>,
  path: Path,
  preserveEmptyStrings: boolean
): Node | undefined {
  const key = path.map(String).join("_")
  const leafValue = emptyStringAsMissing(Object.hasOwn(env, key) ? env[key] : undefined, preserveEmptyStrings)

  const trieNode = trieNodeAt(trie, path)
  const children = trieNode?.children ? Object.keys(trieNode.children) : []

  if (children.length === 0) {
    return leafValue === undefined ? undefined : makeValue(leafValue)
  }

  const allNumeric = children.every((k) => NUMERIC_INDEX.test(k))