1 files changed, 101 insertions, 0 deletions
diff --git a/tools/atlas/parse_requires.nim b/tools/atlas/parse_requires.nim
new file mode 100644
index 000000000..7e26a1656
--- /dev/null
+++ b/tools/atlas/parse_requires.nim
@@ -0,0 +1,101 @@
+## Utility API for Nim package managers.
+## (c) 2021 Andreas Rumpf
+
+import std / strutils
+import ".." / compiler / [ast, idents, msgs, syntaxes, options, pathutils]
+
+type
+  NimbleFileInfo* = object
+    requires*: seq[string]
+    srcDir*: string
+    tasks*: seq[(string, string)]
+
+proc extract(n: PNode; conf: ConfigRef; result: var NimbleFileInfo) =
+  case n.kind
+  of nkStmtList, nkStmtListExpr:
+    for child in n:
+      extract(child, conf, result)
+  of nkCallKinds:
+    if n[0].kind == nkIdent:
+      case n[0].ident.s
+      of "requires":
+        for i in 1..<n.len:
+          var ch = n[i]
+          while ch.kind in {nkStmtListExpr, nkStmtList} and ch.len > 0: ch = ch.lastSon
+          if ch.kind in {nkStrLit..nkTripleStrLit}:
+            result.requires.add ch.strVal
+          else:
+            localError(conf, ch.info, "'requires' takes string literals")
+      of "task":
+        if n.len >= 3 and n[1].kind == nkIdent and n[2].kind in {nkStrLit..nkTripleStrLit}:
+          result.tasks.add((n[1].ident.s, n[2].strVal))
+      else: discard
+  of nkAsgn, nkFastAsgn:
+    if n[0].kind == nkIdent and cmpIgnoreCase(n[0].ident.s, "srcDir") == 0:
+      if n[1].kind in {nkStrLit..nkTripleStrLit}:
+        result.srcDir = n[1].strVal
+      else:
+        localError(conf, n[1].info, "assignments to 'srcDir' must be string literals")
+  else:
+    discard
+
+proc extractRequiresInfo*(nimbleFile: string): NimbleFileInfo =
+  ## Extract the `requires` information from a Nimble file. This does **not**
+  ## evaluate the Nimble file. Errors are produced on stderr/stdout and are
+  ## formatted as the Nim compiler does it. The parser uses the Nim compiler
+  ## as an API. The result can be empty, this is not an error, only parsing
+  ## errors are reported.
+  var conf = newConfigRef()
+  conf.foreignPackageNotes = {}
+  conf.notes = {}
+  conf.mainPackageNotes = {}
+
+  let fileIdx = fileInfoIdx(conf, AbsoluteFile nimbleFile)
+  var parser: Parser
+  if setupParser(parser, fileIdx, newIdentCache(), conf):
+    extract(parseAll(parser), conf, result)
+    closeParser(parser)
+
+const Operators* = {'<', '>', '=', '&', '@', '!', '^'}
+
+proc token(s: string; idx: int; lit: var string): int =
+  var i = idx
+  if i >= s.len: return i
+  while s[i] in Whitespace: inc(i)
+  case s[i]
+  of Letters, '#':
+    lit.add s[i]
+    inc i
+    while i < s.len and s[i] notin (Whitespace + {'@', '#'}):
+      lit.add s[i]
+      inc i
+  of '0'..'9':
+    while i < s.len and s[i] in {'0'..'9', '.'}:
+      lit.add s[i]
+      inc i
+  of '"':
+    inc i
+    while i < s.len and s[i] != '"':
+      lit.add s[i]
+      inc i
+    inc i
+  of Operators:
+    while i < s.len and s[i] in Operators:
+      lit.add s[i]
+      inc i
+  else:
+    lit.add s[i]
+    inc i
+  result = i
+
+iterator tokenizeRequires*(s: string): string =
+  var start = 0
+  var tok = ""
+  while start < s.len:
+    tok.setLen 0
+    start = token(s, start, tok)
+    yield tok
+
+when isMainModule:
+  for x in tokenizeRequires("jester@#head >= 1.5 & <= 1.8"):
+    echo x