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7572 :: How to generate import statement in macros?

• hronro (orginal) [2021-03-02T15:35:29+01:00] view original

  # main.nim
  import macros
  macro gen_import(): untyped =
    return newNimNode(nnkImportStmt).add infix(
      ident("foo"),
      "as",
      ident("bar")
    )
  gen_import()
  echo bar.foobar
  Run

  # foo.nim
  const foobar* = "foobar"
  Run

  I got this error:

  
  lib/core/macros.nim(1348, 13) Error: cannot open file: foo
  Run

  How can I fix this error?

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• cblake (orginal) [2021-03-02T19:43:26+01:00] view original

  Like this:

  import macros
  macro gen_import(): untyped =
    let module = ident("foo")
    let alias  = ident("bar")
    result = quote do:
      import `module` as `alias`
  gen_import()
  echo bar.foobar
  Run

  Your original form worked for me for modules in my explicit nim --path from a nim.cfg (like cligen), but not in the implicit PWD path your foo example used. Not sure why.

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• shirleyquirk (orginal) [2021-03-02T20:05:02+01:00] view original

  macro gen_import():untyped =
    quote do:
      import foo as bar
  Run

  works, not sure how/why sorry

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• cblake (orginal) [2021-03-02T20:09:38+01:00] view original

  I assumed there was some reason @hronro was starting from strings "foo" and "bar" instead of just saying import foo as bar as a statement without any macros at all. So, I thought I should leave those in. :-)

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• shirleyquirk (orginal) [2021-03-02T20:31:42+01:00] view original

  i didn't see your answer! should always refresh before posting, when will i learn

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