Merge pull request #10 from etsy/feat-custom-arch

feat: add custom arch support w/ env var

README.md

@@ -23,6 +23,16 @@ A seamless launcher for Terraform.
 
 Simply navigate to any folder that contains Terraform configuration and run `terraform` as you usually would. `terraform-demux` will attempt to locate the appropriate [version constraint](https://www.terraform.io/docs/language/expressions/version-constraints.html) by searching in the current working directory and recursively through parent directories. If `terraform-demux` cannot determine a constraint, it will default to the latest possible version.
 
+### Architecture Compatability
+
+`terraform-demux` supports a native `arm64` build that can also run `amd64` versions of `terraform` by specifying the `TF_DEMUX_ARCH` environment variable. This might be necessary for `terraform` workspaces that need older `terraform` versions that do not have `arm64` builds, or use older providers that do not have `arm64` builds.
+
+It is recommended to set up the following shell alias for handy `amd64` invocations:
+
+```sh
+alias terraform-amd64="TF_DEMUX_ARCH=amd64 terraform-demux"
+```
+
 ### Logging
 
 Setting the `TF_DEMUX_LOG` environment variable to any non-empty value will cause `terraform-demux` to write out debug logs to `stderr`.

cmd/terraform-demux/main.go

@@ -4,6 +4,7 @@ import (
  "io/ioutil"
  "log"
  "os"
+ "runtime"
 
  "github.com/etsy/terraform-demux/internal/wrapper"
 )
@@ -17,9 +18,15 @@ func main() {
  log.SetOutput(ioutil.Discard)
  }
 
- log.Printf("terraform-demux version %s", version)
+ arch := os.Getenv("TF_DEMUX_ARCH")
 
- exitCode, err := wrapper.RunTerraform(os.Args[1:])
+ if arch == "" {
+ arch = runtime.GOARCH
+ }
+
+ log.Printf("terraform-demux version %s, using arch '%s'", version, arch)
+
+ exitCode, err := wrapper.RunTerraform(os.Args[1:], arch)
 
  if err != nil {
  log.SetOutput(os.Stderr)

internal/wrapper/wrapper.go

@@ -18,7 +18,7 @@ import (
  "github.com/pkg/errors"
 )
 
-func RunTerraform(args []string) (int, error) {
+func RunTerraform(args []string, arch string) (int, error) {
  cacheDirectory, err := ensureCacheDirectory()
 
  if err != nil {
@@ -53,7 +53,7 @@ func RunTerraform(args []string) (int, error) {
 
  log.Printf("version '%s' matches all constraints", matchingRelease.Version)
 
- executablePath, err := client.DownloadRelease(matchingRelease, runtime.GOOS, runtime.GOARCH)
+ executablePath, err := client.DownloadRelease(matchingRelease, runtime.GOOS, arch)
 
  if err != nil {
  return 1, err