Skills template-validation

Name: template-validation
Author: dotnet

install

source · Clone the upstream repo

git clone https://github.com/dotnet/skills

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/dotnet/skills "$T" && mkdir -p ~/.claude/skills && cp -r "$T/plugins/dotnet-template-engine/skills/template-validation" ~/.claude/skills/dotnet-skills-template-validation && rm -rf "$T"

manifest: plugins/dotnet-template-engine/skills/template-validation/SKILL.md

source content

Template Validation

This skill helps validate custom

dotnet new

templates for correctness before publishing. It encodes the validation rules that catch common authoring mistakes — issues that cause templates to silently fail, produce broken projects, or not appear in

dotnet new list

When to Use

User asks to check or validate a template.json file
User reports "my template doesn't show up after installing"
User wants to review a template before packaging and publishing to NuGet
User encounters unexpected behavior from a custom template

When Not to Use

User wants to find or use existing templates — route to
```
template-discovery
```
User wants to create a project — route to
```
template-instantiation
```
User wants to create a template from an existing project — route to
```
template-authoring
```

Inputs

Input	Required	Description
template.json path	Yes	Path to the template.json file or the template directory containing `.template.config/template.json`

Validation Rules

When reviewing a template.json, check ALL of the following categories systematically. Report every finding as an error, warning, or suggestion.

1. Required Fields

Field	Severity	Rule
`identity`	ERROR	Must be present and non-empty
`name`	ERROR	Must be present and non-empty
`shortName`	ERROR	Must be present and non-empty
`sourceName`	WARNING	Without it, `--name` won't customize the generated project name
`author`	WARNING	Improves template discoverability
`description`	SUGGESTION	Helps users understand what the template creates
`classifications`	SUGGESTION	Improves search and categorization (e.g., `["Web", "API"]` )
`defaultName`	SUGGESTION	Provides a fallback project name when `--name` is not specified

2. Identity Format

ERROR if identity contains spaces — use dots or dashes (e.g.,
```
MyCompany.WebApi.CSharp
```
)
WARNING if identity has no namespace separator (
```
.
```
or
```
-
```
) — use reverse-DNS format

3. ShortName Conflicts

The following short names conflict with dotnet CLI commands and will cause problems:

new

build

run

test

publish

restore

clean

pack

add

remove

list

nuget

tool

sln

help

ERROR if shortName matches any reserved name (case-insensitive)
WARNING if shortName is only 1 character — too short for discoverability
Note: shortName can be a string or an array of strings; check all values

4. Symbol Validation

For each symbol in the

symbols

object:

ERROR if a symbol is missing the
```
type
```
field
For
```
type: "parameter"
```
:
- WARNING if no
```
datatype
```
  specified (defaults to
```
string
```
  )
- SUGGESTION if no
```
description
```
  (improves
```
--help
```
  output)
- If
```
datatype: "choice"
```
  :
  - ERROR if no
```
choices
```
    defined
  - ERROR if
```
choices
```
    is empty
  - ERROR if
```
defaultValue
```
    is not in the choices list
  - WARNING if optional (not
```
isRequired
```
    ) and no
```
defaultValue
```
    — users get unexpected behavior
- If
```
datatype: "bool"
```
  :
  - ERROR if
```
defaultValue
```
    is not a valid boolean
- If
```
datatype: "int"
```
  :
  - ERROR if
```
defaultValue
```
    is not a valid integer
- Valid datatypes:
```
string
```
  ,
```
bool
```
  ,
```
choice
```
  ,
```
int
```
  ,
```
float
```
  ,
```
hex
```
  ,
```
text
```
- ERROR if datatype is not in the valid list
For
```
type: "computed"
```
:
- ERROR if missing
```
value
```
  expression

For

type: "generated"

ERROR if missing
```
generator
```
field

Valid generators:

casing

coalesce

constant

port

guid

now

random

regex

regexMatch

switch

join

Parameter prefix collisions: WARNING if any parameter name is a prefix of another parameter name (e.g.,

Auth

and

AuthMode

) — this creates ambiguous parsing in expression contexts.

5. Sources Validation

For source modifier conditions:

WARNING if a condition string doesn't contain parentheses around symbol names — expected format is
```
(symbolName)
```
, not bare
```
symbolName
```

6. Post-Action Validation

For each post-action:

ERROR if missing
```
actionId
```
WARNING if missing
```
description
```
— this text is shown to users when the action requires manual steps
SUGGESTION if missing
```
manualInstructions
```
— these are shown when the action can't run automatically (e.g., in an IDE)

7. Constraint Validation

For each constraint:

ERROR if missing
```
type
```
field
WARNING if missing
```
args
```
— most constraint types require arguments

8. Tags Validation

SUGGESTION if no
```
language
```
tag — adding
```
tags.language
```
(e.g.,
```
"C#"
```
) improves filtering in
```
dotnet new list --language
```
SUGGESTION if no
```
type
```
tag — adding
```
tags.type
```
(e.g.,
```
"project"
```
or
```
"item"
```
) improves categorization

Workflow

Step 1: Locate the template.json

The file can be at:

Direct path:
```
path/to/template.json
```
In a template directory:
```
path/to/.template.config/template.json
```

In a

.template.config

directory:

path/.template.config/template.json

Step 2: Parse and validate

Read the JSON. If it's malformed, report the JSON parse error with line number.

Run all 8 validation categories above. Collect errors, warnings, and suggestions separately.

Step 3: Report results

Present findings organized by severity:

Errors (must fix) — template will not work correctly
Warnings (should fix) — template may cause confusion or limited functionality
Suggestions (nice to have) — improvements for discoverability and user experience

Include the total: "X error(s), Y warning(s), Z suggestion(s)"

Common Pitfalls

Pitfall	Impact
ShortName = "test" or "build"	Template can never be created — conflicts with CLI
Missing `sourceName`	`--name MyProject` doesn't rename anything in the generated files
Choice parameter without `defaultValue`	Confusing user experience on optional choice params
Invalid `datatype` value	Template engine ignores the symbol, causing silent failures
Computed symbol without `value`	Template engine throws at instantiation time
Parameter prefix collision ( `Auth` vs `AuthMode` )	Ambiguous expression evaluation
Source condition without parentheses	Condition may not evaluate correctly

More Info

template.json reference — full schema
Available Symbol Generators — generator types
Post-action registry — action IDs
Constraints — constraint types