# Errors (/docs/errors)

tyfigo collects every problem in a config and its layers and reports them together, each as
`file:line:column - message (code)`.

## Problem codes [#problem-codes]

| Code                  | tsc          | Meaning                                                                                    |
| --------------------- | ------------ | ------------------------------------------------------------------------------------------ |
| `parse-error`         | `tyfigo1001` | The file is not valid for its format                                                       |
| `duplicate-key`       | `tyfigo1002` | A key appears twice                                                                        |
| `file-not-found`      |              | The imported config file doesn't exist                                                     |
| `read-error`          |              | A config or `.env` file exists but can't be read                                           |
| `unsupported-file`    | `tyfigo1005` | The file isn't a config file, or (in tsc) its extension isn't one tyfigo reads             |
| `missing-variable`    |              | A `${VAR}` or `${VAR:?message}` placeholder has no value                                   |
| `invalid-placeholder` | `tyfigo1007` | A placeholder such as `${1PORT}` or an unclosed `${PORT`                                   |
| `unknown-key`         | `TS2353`     | An environment or local file sets a key the base file doesn't have                         |
| `type-mismatch`       | `TS2322`     | An environment or local file changes the kind of a value                                   |
| `browser-placeholder` |              | A browser build imports a file with a placeholder ([Browser builds](/docs/browser-builds)) |
| `placeholder-type`    |              | A variable doesn't read as its placeholder's type ([Placeholders](/docs/placeholders))     |

In tsc, `unknown-key` and `type-mismatch` are ordinary TypeScript errors at the line in the config file. See
[Type checking](/docs/type-checking) for real output.

## At run time [#at-run-time]

A config import that has problems throws when it is evaluated, and the import fails:

```txt
ConfigModuleError: Invalid config /srv/app/config/app.config.yaml
/srv/app/config/app.production.config.yaml:3:3 - 'server.hostname' is not in app.config.yaml; environment and local files can only override existing keys (unknown-key)
/srv/app/config/app.production.config.yaml:4:11 - Expected array at 'features' as in app.config.yaml, got number (type-mismatch)
```

The error has `_tag: 'ConfigModuleError'`, the base `file`, and the `problems` array, each with `file`, `line`, `column`,
`message` and `code`.

## In builds [#in-builds]

Bundler plugins fail the build with the same message. Server bundles leave `missing-variable` and `placeholder-type` to the
start of the server, since the variables come from where it runs.

## Schema errors [#schema-errors]

`loadConfig` and `loadEnv` throw (and the Effect versions fail with) a
[`ConfigValidationError`](/docs/schemas#configvalidationerror):

```txt
Invalid config /srv/app/config/app.config.yaml:
  /srv/app/config/app.config.yaml:2:9 - server.port: Too small: expected number to be >=1
```

## Async schemas [#async-schemas]

`loadConfig` and `loadEnv` throw a `TypeError` naming `loadConfigAsync` and `loadEnvAsync` when the schema validates
asynchronously.