The tfupdate mainly uses the hclwrite parser to preserve comments, but the hclwrite doesn't have enough AST for an object type, as a compromise, the tfupdate also uses the hclsyntax parser to detect old version.
It's not directly related version updating but it contains provider references and it causes a parse error without an EvalContext.
The ideal solution would be extending the hclwrite to be able to parse such a complicated object, but it's not realistic to expect it to be possible in the short term. So I decided to add a new hack on top of the existing hack to achieve the short term goal.
After seeking a temporary solution, I found that the terraform-config-inspect parses the configuration_aliases by using a hcl.ExprMap which doesn't require to decode fully references.
I feel the implementation is messy and fragile. It's probably better not to re-implement by ourselves and depend on the terraform-config-inspect. However the terraform-config-inspect loads a root module not a file, and the current implementation of tfupdate detects and updates version in a single file. It's hard to use it for now. Using the terraform-config-inspect would require additional refactors for splitting the implementation to detecting and updating. To minimize the patch, I fixed only how to parse the required_providers block.
Fixes #40
The tfupdate mainly uses the hclwrite parser to preserve comments, but the hclwrite doesn't have enough AST for an object type, as a compromise, the tfupdate also uses the hclsyntax parser to detect old version.
Terraform v0.15 introduced a new configuration_aliases syntax. https://www.terraform.io/upgrade-guides/0-15.html#alternative-provider-configurations-within-modules
It's not directly related version updating but it contains provider references and it causes a parse error without an EvalContext.
The ideal solution would be extending the hclwrite to be able to parse such a complicated object, but it's not realistic to expect it to be possible in the short term. So I decided to add a new hack on top of the existing hack to achieve the short term goal.
After seeking a temporary solution, I found that the terraform-config-inspect parses the configuration_aliases by using a hcl.ExprMap which doesn't require to decode fully references.
I feel the implementation is messy and fragile. It's probably better not to re-implement by ourselves and depend on the terraform-config-inspect. However the terraform-config-inspect loads a root module not a file, and the current implementation of tfupdate detects and updates version in a single file. It's hard to use it for now. Using the terraform-config-inspect would require additional refactors for splitting the implementation to detecting and updating. To minimize the patch, I fixed only how to parse the required_providers block.