thothctl

Customizing Project Structure Rules

Overview

ThothCTL validates project structure using rules defined in TOML files. You can override the built-in rules by placing a .thothcf.toml file in your project root with a [project_structure] section.

How Rule Resolution Works

thothctl check project iac
         │
         ▼
  Is there a .thothcf.toml in the project directory
  with a [project_structure] section?
         │
    ┌────┴────┐
    │ YES     │ NO
    ▼         ▼
  Use your    Check [thothcf].project_type
  custom      in .thothcf.toml
  rules       │
              ├─ "terragrunt" → built-in terragrunt template
              ├─ (default)    → built-in stack template
              └─ -p module    → built-in module template

Key point: If your .thothcf.toml contains [project_structure], it replaces the built-in rules entirely. There is no partial merge — you must define the complete set of rules you want enforced.

Rule File Location

The override file must be:

Named .thothcf.toml
Located in the directory being checked (the project root, or the path passed with -d)

# Checks ./  for .thothcf.toml
thothctl check project iac

# Checks ./infra/ for .thothcf.toml
thothctl -d ./infra check project iac

Schema Reference

[project_structure]
# Files required at the project root
root_files = [
    ".gitignore",
    "README.md",
    "main.tf"
]

# Folders to skip during validation
ignore_folders = [
    ".git",
    ".terraform",
    "node_modules"
]

# Folder rules (repeatable section)
[[project_structure.folders]]
name = "modules"          # Folder name
mandatory = true          # true = fail if missing, false = warn only
type = "root"             # "root" = top-level, "child" = nested
content = [               # Files required inside this folder
    "main.tf",
    "variables.tf",
    "outputs.tf"
]

[[project_structure.folders]]
name = "examples"
mandatory = true
type = "child"            # This folder is nested inside another
parent = "modules"        # Parent folder name

[[project_structure.folders]]
name = "complete"
mandatory = true
type = "child"
parent = "examples"       # Nested under examples (which is under modules)
content = [
    "main.tf",
    "README.md"
]

Field Reference

Field	Required	Description
`root_files`	Yes	List of files that must exist at project root
`ignore_folders`	No	Folders excluded from validation
`folders[].name`	Yes	Folder name to validate
`folders[].mandatory`	Yes	`true` = error if missing, `false` = informational
`folders[].type`	Yes	`"root"` (top-level) or `"child"` (nested)
`folders[].parent`	If type=child	Name of the parent folder
`folders[].content`	No	Files required inside this folder

Folder Hierarchy

Use type and parent to define nested structures:

# Validates: project/modules/networking/main.tf
[[project_structure.folders]]
name = "modules"
mandatory = true
type = "root"
content = ["main.tf", "variables.tf", "outputs.tf"]

# Validates: project/modules/examples/
[[project_structure.folders]]
name = "examples"
mandatory = true
type = "child"
parent = "modules"

# Validates: project/modules/examples/complete/main.tf
[[project_structure.folders]]
name = "complete"
mandatory = true
type = "child"
parent = "examples"
content = ["main.tf", "terraform.tfvars"]

End-to-End Example

Goal: Enforce that all projects have a security/ folder with iam.tf and policies.tf, plus a monitoring/ folder.

1. Create `.thothcf.toml` in your project root

[project_structure]
root_files = [
    ".gitignore",
    "README.md",
    "root.hcl",
    ".pre-commit-config.yaml"
]

ignore_folders = [
    ".git",
    ".terraform",
    ".terragrunt-cache"
]

[[project_structure.folders]]
name = "modules"
mandatory = true
type = "root"
content = ["main.tf", "variables.tf", "outputs.tf"]

[[project_structure.folders]]
name = "security"
mandatory = true
type = "root"
content = ["iam.tf", "policies.tf"]

[[project_structure.folders]]
name = "monitoring"
mandatory = true
type = "root"
content = ["dashboards.tf", "alarms.tf"]

[[project_structure.folders]]
name = "environments"
mandatory = true
type = "root"

[[project_structure.folders]]
name = "docs"
mandatory = false
type = "root"

2. Run validation

# Soft mode (reports issues, exit 0)
thothctl check project iac -m soft

# Strict mode (fails CI if structure doesn't match)
thothctl check project iac -m strict

3. Expected output

╭─────────────────────────────────────────────────────────────────╮
│ 🏗️ Infrastructure as Code Stack Structure Check                │
╰─────────────────────────────────────────────────────────────────╯
Using Custom options

                        🏗️ Root Structure
╭──────────────┬──────┬──────────┬──────────┬─────────────────────╮
│ Item         │ Type │ Required │ Status   │ Details             │
├──────────────┼──────┼──────────┼──────────┼─────────────────────┤
│ modules      │ 📁   │ Required │ ✅ Pass  │ .                   │
│ security     │ 📁   │ Required │ ✅ Pass  │ .                   │
│ monitoring   │ 📁   │ Required │ ❌ Fail  │ Folder missing      │
│ environments │ 📁   │ Required │ ✅ Pass  │ .                   │
│ docs         │ 📁   │ Optional │ ⚠️ Warn  │ Not found           │
╰──────────────┴──────┴──────────┴──────────┴─────────────────────╯

Built-in Templates

ThothCTL ships with three built-in templates. Use these as starting points for customization:

Stack (default)

Used when running thothctl check project iac -p stack without a local override.

Root files	Mandatory folders
`.gitignore`, `.pre-commit-config.yaml`, `README.md`, `root.hcl`	`common`, `docs`, `modules`, `stacks`

Stack (terragrunt variant)

Used when .thothcf.toml has [thothcf] project_type = "terragrunt".

Same as default stack but with adjusted stacks/ content requirements (includes terragrunt.hcl).

Module

Used when running thothctl check project iac -p module.

Root files	Mandatory folders
`.git`, `.gitignore`, `.pre-commit-config.yaml`, `README.md`	`docs`, `examples` (with `complete/` child)

To see the full definition:

cat $(python -c "import thothctl; import os; print(os.path.dirname(thothctl.__file__))")/common/.thothcf_project.toml

Scaffold Templates (for `init project`)

Scaffold templates use the same .thothcf.toml format but add a [template_input_parameters] section for variable substitution during project creation.

Template Input Parameters

[template_input_parameters.project_name]
template_value = "#{ProjectName}#"     # Placeholder in template files
condition = "^[a-z][a-z0-9_-]+$"       # Regex validation
description = "Project name (lowercase, hyphens allowed)"

[template_input_parameters.region]
template_value = "#{Region}#"
condition = "^[a-z]{2}-[a-z]+-\\d$"
description = "AWS region (e.g., us-east-1)"

[template_input_parameters.environment]
template_value = "#{Environment}#"
condition = "(dev|staging|prod)"
description = "Target environment"

When generating from a template, ThothCTL:

Parses [template_input_parameters] from the template’s .thothcf.toml
Prompts for each parameter (or accepts --variables JSON)
Validates input against condition regex
Replaces all #{ParameterName}# occurrences in generated files

IDP Metadata

Templates can include metadata for Internal Developer Platform catalog integration:

[idp]
tags = ["terraform", "aws", "networking", "module"]

[idp.spec]
lifecycle = "production"
owner = "platform-team"
system = "IaCPlatform"
type = "template"

This metadata is used by thothctl list templates and can be published to Backstage or similar catalogs.

Tips

Start from a built-in template — Copy the default and modify it rather than writing from scratch.
Use mandatory = false for folders you want to track but not enforce yet (shows as warnings in soft mode).
CI/CD — Commit your .thothcf.toml to version control so all team members validate against the same rules.
Per-space standards — Store your organization’s .thothcf.toml in the Space’s templates/ directory and copy it into new projects during init project.

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