❯ cat terragrunt.hcl 
include "foo" {
  path = "../bar_1/terragrunt.hcl"
}

include "foo" {
  path = "../bar_2/terragrunt.hcl"
}

inputs = {
  local = "local"
}

❯ cat ../bar_1/terragrunt.hcl 
inputs = {
  bar_1 = "bar_1"
}

❯ cat ../bar_2/terragrunt.hcl
inputs = {
  bar_2 = "bar_2"
}

❯ terragrunt render
17:15:38.898 INFO   Rendering config ./terragrunt.hcl
inputs = {
  bar_1 = "bar_1"
  bar_2 = "bar_2"
  local = "local"
}

❯ cat terragrunt.hcl 
include "foo" {
  path = "../baz/terragrunt.hcl"
}

include "bar" {
  path = "../baz/terragrunt.hcl"
}

inputs = {
  local = "local"
}

❯ cat ../baz/terragrunt.hcl 
inputs = {
  included = "included"
}

❯ terragrunt render
17:12:20.501 INFO   Rendering config ./terragrunt.hcl
inputs = {
  included = "included"
  local    = "local"
}

❯ cat terragrunt.hcl  
dependency "foo" {
  config_path = "../bar_1"
  mock_outputs = {
    path = "../bar_1"
  }
}
dependency "foo" {
  config_path = "../bar_2"
  mock_outputs = {
    path = "../bar_2"
  }
}

inputs = {
  "foo_path" = dependency.foo.outputs.path
}

❯ terragrunt render 
16:40:19.999 WARN   Failed to read outputs from ../bar_2/terragrunt.hcl referenced in ./terragrunt.hcl as foo, fallback to mock outputs. Error: Did not find any Terraform files (*.tf) or OpenTofu files (*.tofu) in ../bar_2
16:40:19.999 WARN   Failed to read outputs from ../bar_1/terragrunt.hcl referenced in ./terragrunt.hcl as foo, fallback to mock outputs. Error: Did not find any Terraform files (*.tf) or OpenTofu files (*.tofu) in ../bar_1
16:40:20.000 WARN   Config ../bar_2/terragrunt.hcl is a dependency of ./terragrunt.hcl that has no outputs, but mock outputs provided and returning those in dependency output.
16:40:20.000 WARN   Config ../bar_1/terragrunt.hcl is a dependency of ./terragrunt.hcl that has no outputs, but mock outputs provided and returning those in dependency output.
16:40:20.000 INFO   Rendering config ./terragrunt.hcl
dependency "foo" {
  config_path = "../bar_2"
  mock_outputs = {
    path = "../bar_2"
  }
}
dependency "foo" {
  config_path = "../bar_2"
  mock_outputs = {
    path = "../bar_2"
  }
}
inputs = {
  foo_path = "../bar_1"
}

❯ cat terragrunt.hcl
dependency "foo" {
  config_path = "../baz"
  mock_outputs = {
    path = "../baz"
  }
}
dependency "bar" {
  config_path = "../baz"
  mock_outputs = {
    path = "../baz"
  }
}

inputs = {
  "foo_path" = dependency.foo.outputs.path
  "bar_path" = dependency.foo.outputs.path
}

❯ terragrunt render 
16:37:29.115 WARN   Failed to read outputs from ../baz/terragrunt.hcl referenced in ./terragrunt.hcl as bar, fallback to mock outputs. Error: Did not find any Terraform files (*.tf) or OpenTofu files (*.tofu) in ../baz
16:37:29.115 WARN   Config ../baz/terragrunt.hcl is a dependency of ./terragrunt.hcl that has no outputs, but mock outputs provided and returning those in dependency output.
16:37:29.116 WARN   Failed to read outputs from ../baz/terragrunt.hcl referenced in ./terragrunt.hcl as foo, fallback to mock outputs. Error: Did not find any Terraform files (*.tf) or OpenTofu files (*.tofu) in ../baz
16:37:29.116 WARN   Config ../baz/terragrunt.hcl is a dependency of ./terragrunt.hcl that has no outputs, but mock outputs provided and returning those in dependency output.
16:37:29.116 INFO   Rendering config ./terragrunt.hcl
dependency "foo" {
  config_path = "../baz"
  mock_outputs = {
    path = "../baz"
  }
}
dependency "bar" {
  config_path = "../baz"
  mock_outputs = {
    path = "../baz"
  }
}
inputs = {
  bar_path = "../baz"
  foo_path = "../baz"
}