HCL is a file format used to by Terraform and OpenTofu.

This page describe how to add HCL file syntax highlighting to Geany.

Add the following lines to ~/.config/geany/filetype_extensions.conf under the respective sections [Extensions] and [Groups]

[Extensions]
HCL=*.tf;*.tfvars;*.hcl;

Save the configuration file below in your Geany filetype definition files config directory, e.g. ~/.config/geany/filedefs/filetypes.HCL.conf

filetypes.HCL.conf

# For complete documentation of this file, please see Geany's main documentation
[styling=C]
preprocessor=comment
 
[keywords]
# all items must be in one line
primary=data local locals module provider resource terraform var
 
[lexer_properties=C]
styling.within.preprocessor=0
 
[settings]
# default extension used when saving files
extension=tf
lexer_filetype=C
tag_parser=Terraform
 
# the following characters are these which a "word" can contains, see documentation
#wordchars=_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
 
# single comments, like # in this file
comment_single=#
#comment_single=//
# multiline comments
comment_open=/*
comment_close=*/
 
# set to false if a comment character/string should start at column 0 of a line, true uses any
# indentation of the line, e.g. setting to true causes the following on pressing CTRL+d
  #command_example();
# setting to false would generate this
# command_example();
# This setting works only for single line comments
comment_use_indent=true
 
# context action command (please see Geany's main documentation for details)
#context_action_cmd=
 
[indentation]
width=2
# 0 is spaces, 1 is tabs, 2 is tab & spaces
type=0
 
[build-menu]
FT_00_LB=Plan
FT_00_CM=terraform plan -no-color
FT_00_WD=%d
EX_00_LB=Apply
EX_00_CM=terraform apply
EX_00_WD=%d
EX_01_LB=Destroy
EX_01_CM=terraform destroy
EX_01_WD=%d
FT_01_LB=Init
FT_01_CM=terraform init -no-color
FT_01_WD=%d

If you are using the Geany-LSP plugin (https://plugins.geany.org/lsp.html) for additional editing assistance, you can also use the Terraform language server. The Geany-LSP plugin already includes the corresponding configuration for the filetype HCL.

You only need to install the language server from https://github.com/hashicorp/terraform-ls or https://github.com/opentofu/opentofu-ls.