Struct Error

pub struct Error { /* private fields */ }

Represents template errors.

If debug mode is enabled a template error contains additional debug information that can be displayed by formatting an error with the alternative formatting (format!("{:#}", err)). That information is also shown for the Debug display where the extended information is hidden when the alternative formatting is used.

Since MiniJinja takes advantage of chained errors it’s recommended to render the entire chain to better understand the causes.

Example

Here is an example of how you might want to render errors:

match template.render(ctx) {
    Ok(result) => println!("{}", result),
    Err(err) => {
        eprintln!("Could not render template: {:#}", err);
        // render causes as well
        let mut err = &err as &dyn std::error::Error;
        while let Some(next_err) = err.source() {
            eprintln!();
            eprintln!("caused by: {:#}", next_err);
            err = next_err;
        }
    }
}

Implementations

impl Error

pub fn new<D: Into<Cow<'static, str>>>(kind: ErrorKind, detail: D) -> Error

Creates a new error with kind and detail.

pub fn with_source<E: Error + Send + Sync + 'static>(self, source: E) -> Self

Attaches another error as source to this error.

pub fn kind(&self) -> ErrorKind

Returns the error kind

pub fn detail(&self) -> Option<&str>

Returns the error detail

The detail is an error message that provides further details about the error kind.

pub fn name(&self) -> Option<&str>

Returns the filename of the template that caused the error.

pub fn line(&self) -> Option<usize>

Returns the line number where the error occurred.

pub fn range(&self) -> Option<Range<usize>>

Returns the byte range of where the error occurred if available.

In combination with template_source this can be used to better visualize where the error is coming from. By indexing into the template source one ends up with the source of the failing expression.

Note that debug mode (Environment::set_debug) needs to be enabled, and the debug feature must be turned on. The engine usually keeps track of spans in all cases, but there is no absolute guarantee that it is able to provide a range in all error cases.

let tmpl = env.template_from_str("Hello {{ foo + bar }}!").unwrap();
let err = tmpl.render(context!(foo => "a string", bar => 0)).unwrap_err();
let src = err.template_source().unwrap();
assert_eq!(&src[err.range().unwrap()], "foo + bar");

pub fn display_debug_info(&self) -> impl Display + '_

Helper function that renders all known debug info on format.

This method returns an object that when formatted prints out the debug information that is contained on that error. Normally this is automatically rendered when the error is displayed but in some cases you might want to decide for yourself when and how to display that information.

pub fn template_source(&self) -> Option<&str>

Returns the template source if available.

Trait Implementations

impl Debug for Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for Error

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl Error for Error

fn custom<T: Display>(msg: T) -> Self

Raised when there is general error when deserializing a type.

fn invalid_type(unexp: Unexpected<'_>, exp: &dyn Expected) -> Self

Raised when a Deserialize receives a type different from what it was expecting.

fn invalid_value(unexp: Unexpected<'_>, exp: &dyn Expected) -> Self

Raised when a Deserialize receives a value of the right type but that is wrong for some other reason.

fn invalid_length(len: usize, exp: &dyn Expected) -> Self

Raised when deserializing a sequence or map and the input data contains too many or too few elements.

fn unknown_variant(variant: &str, expected: &'static [&'static str]) -> Self

Raised when a Deserialize enum type received a variant with an unrecognized name.

fn unknown_field(field: &str, expected: &'static [&'static str]) -> Self

Raised when a Deserialize struct type received a field with an unrecognized name.

fn missing_field(field: &'static str) -> Self

Raised when a Deserialize struct type expected to receive a required field with a particular name but that field was not present in the input.

fn duplicate_field(field: &'static str) -> Self

Raised when a Deserialize struct type received more than one of the same field.

impl From<Error> for Error

fn from(_: Error) -> Self

Converts to this type from the input type.

impl From<Error> for Value

fn from(value: Error) -> Self

Converts to this type from the input type.

impl From<ErrorKind> for Error

fn from(kind: ErrorKind) -> Self

Converts to this type from the input type.

impl<'de> IntoDeserializer<'de, Error> for &'de Value

type Deserializer = &'de Value

The type of the deserializer being converted into.

fn into_deserializer(self) -> &'de Value

Convert this value into a deserializer.

impl<'de> IntoDeserializer<'de, Error> for Value

type Deserializer = Value

The type of the deserializer being converted into.

fn into_deserializer(self) -> Value

Convert this value into a deserializer.