* Add packer fmt command
This change adds a new command that allows users to format one or more
HCL2 Packer configuration template files.
Related to: #9174
* command/fmt: Add check flag
Packer's fmt command now supports a check flag that will output the name
of any file that would be changed by the HCL2 formatting engine. The
check flag is mutually exclusive with the write flag and will only check
if formatting is needed.
The update write flag will now overwrite the source files with the newly
formatted HCL2 source unless the `-write=false` or `-check` is passed at
the command line.
* Returns a diagnostic error if Format is unable to show a diff - equivalent to `terraform fmt`
* Updates testing to run against #Format and not the private methods of the HCL2Formatter; fixes ShowDiff test failure on Windows
* Updates comments for exported functions
* Add docs for fmt command
hcl2_upgrade transforms a JSON build-file in a HCL2 build-file.
This starts a validated Packer core and from that core we generate an HCL 'block' per plugin/configuration. So for a builder, a provisioner, a post-processor or a variable. The contents of each block is just transformed as is and basically all fields are HCL2-ified.
A generated field can be valid in JSON but invalid on HCL2; for example JSON templating (in mapstructure) allows to set arrays of strings - like `x = ["a", "b"]` - with single strings - like `x="a"` -, HCL does not allow this.
Since JSON does not make the distinction between variables and locals, everything will be a variable. So variables that use other variables will not work.
hcl2_upgrade tries to transform go templating interpolation calls to HCL2 calls when possible, leaving the go templating calls like they are in case it cannot.
Work:
* transpiler
* tests
* update hcl v2 library so that output looks great.
* update docs
Megan Marsh
Wilken Rivera
Adrien Delorme
Adrien Delorme
Moss