refactor

plugins/lexiconBarrels.js

@@ -0,0 +1,94 @@
+/*
+ * Shared mechanics for reading the generated lexicon barrels, used by
+ * babel-plugin-lexicon-leaf-imports and its test suites. The tests keep their
+ * own walking logic (an export-graph oracle vs the plugin's filesystem
+ * heuristic); only this mechanical layer - how a specifier resolves to a file
+ * and how a barrel parses into its re-export map - is shared, so the copies
+ * cannot drift apart.
+ */
+const fs = require('node:fs')
+const parser = require('@babel/parser')
+const path = require('node:path')
+
+/** Extensions codegen emits: `.ts` for app sources, `.js` for the SDK dist. */
+const EXTS = ['.ts', '.js']
+const EXT_RE = new RegExp(`\\.(${EXTS.map(e => e.slice(1)).join('|')})$`)
+
+/** Matches the SDK's compiled barrel entry, e.g. '../lexicons/index.js'. */
+const SDK_BARREL_RE = /(^|\/)lexicons\/index\.js$/
+
+/**
+ * Resolve a barrel/leaf specifier relative to the importing file: the exact
+ * path when it already carries a known extension, otherwise the first of
+ * EXTS that exists.
+ *
+ * @param {string} fromFile
+ * @param {string} spec
+ * @returns {string | null} absolute file path, or null
+ */
+function resolveModuleFile(fromFile, spec) {
+  const abs = path.resolve(path.dirname(fromFile), spec)
+  if (EXT_RE.test(abs) && fs.existsSync(abs)) return abs
+  for (const ext of EXTS) {
+    if (fs.existsSync(abs + ext)) return abs + ext
+  }
+  return null
+}
+
+/** Absolute barrel file -> Map(exported name -> source specifier), or null. */
+const barrelExportCache = new Map()
+
+/**
+ * Parse a barrel file into its namespace re-export map. Returns null if the
+ * file contains anything other than `export * as X from '...'` statements
+ * (plus type-only exports) - chains through such a file cannot be proven, so
+ * lookups fail and the caller bails.
+ *
+ * @param {string} file
+ * @returns {Map<string, string> | null}
+ */
+function barrelExports(file) {
+  let map = barrelExportCache.get(file)
+  if (map !== undefined) return map
+  map = new Map()
+  try {
+    const ast = parser.parse(fs.readFileSync(file, 'utf8'), {
+      sourceType: 'module',
+      plugins: ['typescript'],
+    })
+    for (const stmt of ast.program.body) {
+      if (stmt.exportKind === 'type') continue
+      if (
+        stmt.type !== 'ExportNamedDeclaration' ||
+        !stmt.source ||
+        stmt.declaration ||
+        stmt.specifiers.length === 0 ||
+        !stmt.specifiers.every(s => s.type === 'ExportNamespaceSpecifier')
+      ) {
+        map = null
+        break
+      }
+      for (const s of stmt.specifiers) {
+        const name =
+          s.exported.type === 'Identifier' ? s.exported.name : s.exported.value
+        map.set(name, stmt.source.value)
+      }
+    }
+  } catch {
+    map = null
+  }
+  barrelExportCache.set(file, map)
+  return map
+}
+
+function clearBarrelExportCache() {
+  barrelExportCache.clear()
+}
+
+module.exports = {
+  EXTS,
+  SDK_BARREL_RE,
+  resolveModuleFile,
+  barrelExports,
+  clearBarrelExportCache,
+}