validate

Composable validation for Go with fluent builders, rule tags, struct validation, and optional message translation.

Packages

• github.com/aatuh/validate/v3: main API (Validate, builders, FromTag)
• github.com/aatuh/validate/v3/core: generic validation engine (unified, cache-optimized)
• github.com/aatuh/validate/v3/glue: integration layer with builders
• github.com/aatuh/validate/v3/validators: type-specific rules
• github.com/aatuh/validate/v3/errors: error types and codes
• github.com/aatuh/validate/v3/structvalidator: struct validation
• github.com/aatuh/validate/v3/translator: i18n helpers

The package is architecturally separated into:

• Core: Generic validation engine, type-agnostic, with unified caching
• Glue: Integration layer that connects core with type-specific builders
• Validators: Type-specific validation implementations

Quick start

For examples, see the examples package.

Run examples:

# Run all examples in learning order
go test ./examples -v -count 1

# Run specific examples
go test ./examples -v -count 1 -run Test_structTags

Supported data types

Type	Description
string	UTF-8 strings; rune-aware length rules
int	Any Go int type accepted at call time
int64	Requires exactly int64 at call time
slice	Any slice type; supports per-element
bool	Boolean type-check only

Plugin rules that operate on strings (imported by default):

• uuid: validates canonical UUID string
• ulid: validates ULID string
• email: validates email address string

Note on plugin registration:

• validate.New() already registers these plugin validators via blank imports inside the root package.
• If you use core/glue directly, blank-import the plugins yourself:

import (
    _ "github.com/aatuh/validate/v3/validators/email"
    _ "github.com/aatuh/validate/v3/validators/ulid"
    _ "github.com/aatuh/validate/v3/validators/uuid"
)

Tags by type

Tags can be used in struct field tags or with FromTag.

string

Tag	Meaning
len=N	Exact byte length equals N
min=N	Minimum byte length
max=N	Maximum byte length
minRunes=N	Minimum Unicode rune count
maxRunes=N	Maximum Unicode rune count
oneof=a,b,c	Value must be one of the listed values
regex=PATTERN	Full-match against PATTERN (anchors added)
uuid	UUID format (via plugin)
ulid	ULID format (via plugin)
email	Email format (via plugin)

Notes:

• oneof supports comma or space separated values.
• Regex is made safe (anchors added, input length capped).

int / int64

Tag	Meaning
min=N	Minimum numeric value
max=N	Maximum numeric value

Use int64;... to require exactly int64 at validation time; int;... accepts any Go int type (int, int8, int16, int32, int64, and unsigned variants for base type checks).

slice

Tag	Meaning
len=N	Exact slice length
min=N	Minimum slice length
max=N	Maximum slice length
foreach=(...)	Element rules in parentheses, e.g. string rules

Example: slice;min=1;foreach=(string;min=2).

bool

Tag	Meaning
bool	Type check (boolean)

Error codes

Stable constants for programmatic handling (see errors/codes.go):

const (
    // String
    CodeStringMin = "string.min"
    CodeStringMax = "string.max"
    CodeStringNonEmpty = "string.nonempty"
    CodeStringPattern = "string.pattern"
    CodeStringOneOf = "string.oneof"

    // Number (ints/floats)
    CodeNumberMin = "number.min"
    CodeNumberMax = "number.max"

    // Slice
    CodeSliceMin = "slice.min"
    CodeSliceMax = "slice.max"
)