0.12 file() Function usage suggests filebase64() while other functions may be more appropriate

[bflad]

Current Terraform Version

Terraform v0.12.0-beta1

Description

In Terraform 0.12, the file() function only allows UTF-8 content to provide safety against state corruption. Prior to the introduction of the new file hashing functions in #20098, the filebase64() function was the only file conversion/hashing function available and the error messaging was coded to recommend it, however the recommendation can be incorrect in the following situations:

# Terraform 0.11 Usage

resource "aws_lambda_function" "example" {
  filename         = "example.zip"
  function_name    = "example"
  handler          = "exports.example"
  role             = "${aws_iam_role.example.arn}"
  runtime          = "nodejs8.10"
  source_code_hash = "${base64sha256(file("example.zip"))}"
}

resource "aws_s3_bucket_object" "example" {
  bucket = "${aws_s3_bucket.example.id}"
  etag   = "${md5(file("example.tar.gz"))}"
  key    = "example.tar.gz"
  source = "example.tar.gz"
}

config is invalid: Error in function call: Call to function "file" failed: contents of example.zip are not valid UTF-8; to read arbitrary bytes, use the filebase64 function instead.

config is invalid: Error in function call: Call to function "file" failed: contents of example.tar.gz are not valid UTF-8; to read arbitrary bytes, use the filebase64 function instead.

The correct configuration updates here are the filebase64sha256() and filemd5() functions respectively.

Proposal

It would be preferable to remove the explicit filebase64() function recommendation unless we know for certain it is the correct recommendation.

References

• New File Hashing Errors In Terraform 0.12 #20098

[apparentlymart]

I had a feeling this would come up. It is unfortunate, indeed.

I think the compromise I'd like to try here is to reword the message to be clearer about what we have changed: binary data can no longer be used, if a base64-encoded result is suitable then use filebase64 instead, but note that the result will not be the same and so the value will need to be used in a different way.

[ghost]

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