Validify

A procedural macro that provides attributes for field validation and modifiers. Particularly useful in the context of web payloads.

Modifiers

*Also works for Vec<String> by running the modifier on each element.

Validators

All validators also take in a code and message as parameters, their values are must be string literals if specified.

Time operators

All time operators can take in inclusive = bool.

in_period and the *_from_now operators are inclusive by default.

The target param must be a string literal date or a path to an argless function that returns a date[time].

If the target is a string literal, it must contain a format param, as per this.

Accepted interval parameters are seconds, minutes, hours, days, weeks.

The _from_now operators should not use negative duration due to how they validate the inputs, negative duration for in_period works fine.

Annotate the struct you want to modify and validate with the Validify attribute (if you do not need payload modification, derive the validify::Validate trait):

use validify::Validify;

#[derive(Debug, Clone, serde::Deserialize, Validify)]
struct Testor {
    #[modify(lowercase, trim)]
    #[validate(length(equal = 8))]
    pub a: String,
    #[modify(trim, uppercase)]
    pub b: Option<String>,
    #[modify(custom(do_something))]
    pub c: String,
    #[modify(custom(do_something))]
    pub d: Option<String>,
    #[validify]
    pub nested: Nestor,
}

#[derive(Debug, Clone, serde::Deserialize, Validify)]
struct Nestor {
    #[modify(trim, uppercase)]
    #[validate(length(equal = 12))]
    a: String,
    #[modify(capitalize)]
    #[validate(length(equal = 14))]
    b: String,
}

fn do_something(input: &mut String) {
    *input = String::from("modified");
}

let mut test = Testor {
  a: "   LOWER ME     ".to_string(),
  b: Some("  makemeshout   ".to_string()),
  c: "I'll never be the same".to_string(),
  d: Some("Me neither".to_string()),
  nested: Nestor {
    a: "   notsotinynow   ".to_string(),
      b: "capitalize me.".to_string(),
  },
};

// The magic line
let res = Testor::validify(test.into());

assert!(matches!(res, Ok(_)));

let test = res.unwrap();

// Parent
assert_eq!(test.a, "lower me");
assert_eq!(test.b, Some("MAKEMESHOUT".to_string()));
assert_eq!(test.c, "modified");
assert_eq!(test.d, Some("modified".to_string()));
// Nested
assert_eq!(test.nested.a, "NOTSOTINYNOW");
assert_eq!(test.nested.b, "Capitalize me.");

Notice how even though field d is an option, the function used to modify the field still takes in &mut String. This is because modifiers and validations are only executed when the field isn't None.

How it works

Every struct annotated with #[derive(Validify)] gets an associated payload struct, e.g.

#[derive(validify::Validify)]
struct Something {
  a: usize,
  b: String,
  c: Option<bool>
}

behind the scenes will generate an intermediary

#[derive(Debug, Clone, serde::Deserialize, validify::Validate)]
struct SomethingPayload {
  #[validate(required)]
  a: Option<usize>,
  #[validate(required)]
  b: Option<String>,
  c: Option<bool>,

  /* From and Into impls */
}

Note that every field that isn't an option will be an 'optional' required field in the payload. This is done to avoid deserialization errors for missing fields.

• Do note that if a field exists in the incoming client payload, but is of the wrong type, a deserialization error will still occur as the payload is only being validated for whether the necessary fields exist. The same applies for invalid date[time] formats.

Even though the payload struct cannot help with wrong types, it can still prove useful and provide a bit more meaningful error messages when fields are missing.

Struct level annotations, such as #[serde(renameAll = "...")] are propagated to the payload.

When a struct contains nested validifies (child structs annotated with #[validify]), all the children in the payload will also be transformed and validated as payloads first.

Validify exposes two methods for validation/modification;

validify which takes in the payload and validates its required fields first and

validify_self which runs modifications and validations on the original struct, without ever using the payload.

In the context of web, you'll most likely be using validify. As such, the request handler should always take in the payload struct.

The Validify implementation first validates the required fields of the generated payload. If any required fields are missing, no further modification/validation is done and the errors are returned. Next, the payload is transformed to the original struct and modifications and validations are run on it.

Validify's validify method is called from the original struct with the associated payload struct as its argument and outputs the original struct if all validations have passed.

Schema validation

Schema level validations can be performed using the following:

use validify::{Validify, ValidationErrors, schema_validation, schema_err};
#[derive(validify::Validify)]
#[validate(validate_testor)]
struct Testor {
    a: String,
    b: usize,
}

#[schema_validation]
fn validate_testor(t: &Testor) -> Result<(), ValidationErrors> {
  if t.a.as_str() == "yolo" && t.b < 2 {
    schema_err!("Invalid Yolo", "Cannot yolo with b < 2");
  }
}

The #[schema_validation] proc macro expands the function to:

fn validate_testor(t: &Testor) -> Result<(), ValidationErrors> {
    let mut errors = ValidationErrors::new();
    if t.a == "yolo" && t.b < 2 {
        errors.add(ValidationError::new_schema("Invalid Yolo").with_message("Cannot yolo with b < 2".to_string()));
    }
    if errors.is_empty() { Ok(()) } else { Err(errors) }
}

This makes schema validations a bit more ergonomic and concise. Like field level validation, schema level validation is performed after modification.

Errors

The main ValidationError is an enum with 2 variants, Field and Schema. Field errors are, as the name suggests, created when fields fail validation and are usually automatically generated unless using custom handlers (custom field validation functions always must return a result whose Err variant is ValidationError).

If you want to provide a message along with the error, you can directly specify it in the attribute (the same goes for the code), for example:

#[validate(contains(value = "something", message = "Does not contain something", code = "MUST_CONTAIN"))]

Keep in mind, when specifying validations this way, all attribute parameters MUST be specified as NameValue pairs. This means that if you write

#[validate(contains("something", message = "Bla"))],

you will get an error because the parser expects either a single value or multiple name value pairs.

The field_err! macro provides a shorthand for creating field errors when using custom functions.

Location

Locations are tracked for each error in a similar manner to JSON pointers. When using custom validation, whatever field name you specify in the returned error will be used in the location for that field. Keep in mind locations are not reliable when dealing with hashed map/set collections as the item ordering for those is not guaranteed.

Error location display will depend on the original client payload, i.e. they will be displayed in the original case the payload was received (e.g. when using serde's rename_all). Any overriden field names will be displayed as such.

Schema

Schema errors are usually created by the user in schema validation. The schema_err! macro alongside #[schema_validation] provides an ergonomic way to create schema errors. All errors are composed to a ValidationErrors struct which contains a vec of all the validation errors.

Params

When sensible, validify automatically appends failing parameters and the target values they were validated against to the errors created to provide more clarity to the client and to save some manual work.

One parameter that is always appended is the actual field which represents the violating field's value during the validation. Some validators append additional data to the errors representing the expected values for the field.

Examples

Date[times]s

use chrono::{NaiveDate, NaiveDateTime};

#[derive(Debug, validify::Validate)]
struct DateTimeExamples {
    #[validate(time(op = before, target = "2500-04-20", format = "%Y-%m-%d", inclusive = true))]
    before: NaiveDate,
    #[validate(time(op = before, target = "2500-04-20T12:00:00.000", format = "%Y-%m-%-dT%H:%M:%S%.3f"))]
    before_dt: NaiveDateTime,
    #[validate(time(op = after, target = "2022-04-20", format = "%Y-%m-%d"))]
    after: NaiveDate,
    #[validate(time(op = after, target = "2022-04-20T12:00:00.000", format = "%Y-%m-%-dT%H:%M:%S%.3f"))]
    after_dt: NaiveDateTime,
    #[validate(time(op = in_period, target = "2022-04-20", format = "%Y-%m-%d", weeks = -2))]
    period: NaiveDate,
}

With route handler

    use validify::Validify;

    #[derive(Debug, Validify)]
    struct JsonTest {
        #[modify(lowercase)]
        a: String,
        #[modify(trim, uppercase)]
        #[validate(length(equal = 11))]
        b: String,
    }

    // This would normally come from a framework
    struct Json<T>(T);

    fn test() {
      let jt = JsonTest {
          a: "MODIFIED".to_string(),
          b: "    makemeshout    ".to_string(),
      };
      let json = Json(jt.into());
      mock_handler(json)
    }

    fn mock_handler(data: Json<JsonTestPayload>
    /* OR data: Json<<JsonTest as Validify>::Payload> */) {
      let data = data.0;
      let data = JsonTest::validify(data).unwrap();
      mock_service(data);
    }

    fn mock_service(data: JsonTest) {
      assert_eq!(data.a, "modified".to_string());
      assert_eq!(data.b, "MAKEMESHOUT".to_string())
    }

Big Boi

use validify::{Validify, ValidationError, ValidationErrors, schema_validation, schema_err};
use serde::Deserialize;

const WORKING_HOURS: &[&str] = &["08", "09", "10", "11", "12", "13", "14", "15", "16"];
const CAREER_LEVEL: &[&str] = &["One", "Two", "Over 9000"];
const STATUSES: &[&str] = &["online", "offline"];
const CONTRACT_TYPES: &[&str] = &["Fulltime", "Temporary"];
const ALLOWED_MIME: &[&str] = &["jpeg", "png"];
const ALLOWED_DURATIONS: &[i32] = &[1, 2, 3];

#[derive(Clone, Deserialize, Debug, Validify)]
#[serde(rename_all = "camelCase")]
#[validate(schema_validation)]
struct BigBoi {
    #[modify(trim)]
    #[validate(length(max = 300))]
    title: String,

    #[modify(trim)]
    #[validate(is_in(STATUSES))]
    status: String,

    #[modify(capitalize, trim)]
    city_country: String,

    #[validate(length(max = 1000))]
    education: String,

    #[modify(capitalize)]
    type_of_workplace: Vec<String>,

    #[validate(is_in(WORKING_HOURS))]
    working_hours: String,

    part_time_period: Option<String>,

    #[modify(capitalize)]
    #[validate(is_in(CONTRACT_TYPES))]
    contract_type: String,

    indefinite_probation_period: bool,

    #[validate(is_in(ALLOWED_DURATIONS))]
    indefinite_probation_period_duration: Option<i32>,

    #[validate(is_in(CAREER_LEVEL))]
    career_level: String,

    #[modify(capitalize)]
    benefits: String,

    #[validate(length(max = 60))]
    meta_title: String,

    #[validate(length(max = 160))]
    meta_description: String,

    #[validate(is_in(ALLOWED_MIME))]
    meta_image: String,

    #[validate(custom(greater_than_now))]
    published_at: String,

    #[validate(custom(greater_than_now))]
    expires_at: String,

    #[validify]
    languages: Vec<TestLanguages>,

    #[validify]
    tags: TestTags,
}


#[schema_validation]
fn schema_validation(bb: &BigBoi) -> Result<(), ValidationErrors> {
    if bb.contract_type == "Fulltime" && bb.part_time_period.is_some() {
        schema_err!("Fulltime contract cannot have part time period");
    }

    if bb.contract_type == "Fulltime"
        && bb.indefinite_probation_period
        && bb.indefinite_probation_period_duration.is_none()
    {
        schema_err!(
            "No probation duration",
            "Indefinite probation duration must be specified",
        );
    }
}

fn greater_than_now(date: &str) -> Result<(), ValidationError> {
    let parsed = chrono::NaiveDateTime::parse_from_str(date, "%Y-%m-%d %H:%M:%S");
    match parsed {
        Ok(date) => {
            if date
                < chrono::NaiveDateTime::from_timestamp_opt(chrono::Utc::now().timestamp(), 0)
                    .unwrap()
            {
                Err(ValidationError::new_field(
                    "invalid_date",
                ))
            } else {
                Ok(())
            }
        }
        Err(e) => {
            Err(ValidationError::new_field("invalid_date"))
        }
    }
}

#[derive(Deserialize, Debug, Clone, Validify)]
#[serde(rename_all = "camelCase")]
struct TestTags {
    #[modify(trim)]
    #[validate(length(min = 1, max = 10), custom(validate_names))]
    names: Vec<String>,
}

fn validate_names(names: &[String]) -> Result<(), ValidationError> {
    for n in names.iter() {
        if n.len() > 10 || n.is_empty() {
            return Err(ValidationError::new_field(
                "invalid_name"
            ));
        }
    }
    Ok(())
}

const PROFICIENCY: &[&str] = &["dunno", "killinit"];

#[derive(Clone, Deserialize, Debug, Validify)]
#[serde(rename_all = "camelCase")]
struct TestLanguages {
    company_opening_id: String,
    #[modify(trim)]
    language: String,

    #[modify(trim)]
    #[validate(is_in(PROFICIENCY))]
    proficiency: Option<String>,

    required: Option<bool>,
    created_by: String,
}

fn biggest_of_bois() {
  let tags = TestTags {
        // Invalid length due to `validate_names`
        names: vec![
            "taggggggggggggggggggggggggg".to_string(),
            "tag".to_string(),
            "tag".to_string(),
        ],
    };

    let languages = vec![
        TestLanguages {
            company_opening_id: "yolo mcswag".to_string(),
            language: "    tommorrowlang     ".to_string(),

            // Invalid proficiency
            proficiency: Some("invalid      ".to_string()),
            required: Some(true),
            created_by: "me".to_string(),
        },
        TestLanguages {
            company_opening_id: "divops".to_string(),
            language: "go".to_string(),

            // Invalid proficiency
            proficiency: Some("    invalid".to_string()),
            required: None,
            created_by: "they".to_string(),
        },
    ];

    let big = BigBoi {
        title: "me so big".to_string(),

        // Invalid status
        status: "invalid".to_string(),

        city_country: "gradrzava".to_string(),
        education: "any".to_string(),
        type_of_workplace: vec!["dumpster".to_string(), "mcdonalds".to_string()],

        // Invalid working hours
        working_hours: "invalid".to_string(),

        // Part time period with fulltime contract type
        part_time_period: Some(String::new()),
        contract_type: "Fulltime".to_string(),

        // Fulltime period with no duration
        indefinite_probation_period: true,
        indefinite_probation_period_duration: None,

        // Invalid career level
        career_level: "Over 100000".to_string(),

        benefits: "none".to_string(),
        meta_title: "this struct is getting pretty big".to_string(),
        meta_description: "and it's kind of annoying".to_string(),

        // Invalid mime type
        meta_image: "heic".to_string(),

        // Invalid time
        published_at: "1999-01-01 00:00:00".to_string(),

        // Invalid time
        expires_at: "1999-01-01 00:00:00".to_string(),
        languages,
        tags,
    };

    let res = BigBoi::validify(big.into());
    assert!(matches!(res, Err(ref e) if e.errors().len() == 11));

    let schema_errs = res.as_ref().unwrap_err().schema_errors();
    let field_errs = res.unwrap_err().field_errors();

    assert_eq!(schema_errs.len(), 2);
    assert_eq!(field_errs.len(), 9);
}