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Use FieldState to collect validation data
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@ArthurClemens
ArthurClemens committed Sep 24, 2022
1 parent fa4c298 commit 9bfcfab
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Showing 7 changed files with 8,032 additions and 1,898 deletions.
13 changes: 13 additions & 0 deletions lib/field_state.ex
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
defmodule PrimerLive.FieldState do
@moduledoc """
State object with validation data for a particular form field.
Struct fields:
- `changeset` - `Ecto.Changeset` struct.
- `field_errors` - changeset `errors`, filtered for the field.
- `valid?` - True if changeset's `field_errors` is empty for the field.
- `message` - Default message derived from changeset `errors`, unless overridden by `validation_message` attribute.
- `message_id` - Generated id that is used for `aria_describedby`.
"""
defstruct valid?: false, changeset: nil, message: nil, message_id: nil, field_errors: []
end
174 changes: 119 additions & 55 deletions lib/helpers/form_helpers.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -2,19 +2,7 @@ defmodule PrimerLive.Helpers.FormHelpers do
use Phoenix.HTML

@moduledoc false

@doc """
Returns field error data.
Returns nil if no errors are found, or if the form does not contain an `error` attribute.
"""
def error_data(form, field) do
try do
form.errors
|> Keyword.get_values(field)
rescue
_ -> nil
end
end
# Helper functions for components that interact with forms and changesets.

@doc """
Returns the form changeset (from form.source).
Expand All @@ -30,66 +18,142 @@ defmodule PrimerLive.Helpers.FormHelpers do

@doc """
Returns all error for a given field from a changeset.
iex> PrimerLive.Helpers.FormHelpers.get_field_errors(
...> %{
...> action: :update,
...> changes: %{},
...> errors: [],
...> data: nil,
...> valid?: true
...> }, :first_name)
[]
iex> PrimerLive.Helpers.FormHelpers.get_field_errors(
...> %{
...> action: :update,
...> changes: %{},
...> errors: [
...> first_name: {"can't be blank", [validation: :required]},
...> work_experience: {"invalid value", [validation: :required]}
...> ],
...> data: nil,
...> valid?: true
...> }, :first_name)
["can't be blank"]
iex> PrimerLive.Helpers.FormHelpers.get_field_errors(
...> %{
...> action: :update,
...> changes: %{},
...> errors: [
...> first_name: {"can't be blank", [validation: :required]},
...> work_experience: {"invalid value", [validation: :required]}
...> ],
...> data: nil,
...> valid?: true
...> }, :work_experience)
["invalid value"]
"""
def field_errors(changeset, field) do
def get_field_errors(changeset, field) do
changeset.errors
|> Enum.filter(fn {error_field, _content} -> error_field == field end)
|> Enum.map(fn {_error_field, {content, _details}} -> content end)
end

@doc """
Returns a map of validation data to facilitate display logic in component rendering functions.
Returns a `PrimerLive.FieldState` struct to facilitate display logic in component rendering functions.
iex> PrimerLive.Helpers.FormHelpers.field_state(:f, :first_name, nil)
%PrimerLive.FieldState{valid?: false, changeset: nil, message: nil, message_id: nil, field_errors: []}
# If validation_message_fn returns a string it will be added to FieldState, regardless of the changeset action value:
iex> PrimerLive.Helpers.FormHelpers.field_state(
...> %Phoenix.HTML.Form{
...> source: %{
...> action: :update,
...> changes: %{first_name: "annette"},
...> errors: [],
...> data: nil,
...> valid?: true
...> },
...> },
...> :first_name, fn _field_state -> "always" end)
%PrimerLive.FieldState{valid?: true, changeset: %{action: :update, changes: %{first_name: "annette"}, data: nil, errors: [], valid?: true}, message: "always", message_id: "first_name-validation", field_errors: []}
# If changeset action is :validate and no validation_message_fn is provided, the default field error is added to FieldState:
iex> PrimerLive.Helpers.FormHelpers.field_state(
...> %Phoenix.HTML.Form{
...> source: %{
...> action: :validate,
...> changes: %{},
...> errors: [first_name: {"can't be blank", [validation: :required]}],
...> data: nil,
...> valid?: true
...> },
...> },
...> :first_name, nil)
%PrimerLive.FieldState{valid?: false, changeset: %{action: :validate, changes: %{}, data: nil, errors: [first_name: {"can't be blank", [validation: :required]}], valid?: true}, message: "can't be blank", message_id: "first_name-validation", field_errors: ["can't be blank"]}
# If changeset action is :update and no validation_message_fn is provided, no message is added to FieldState:
iex> PrimerLive.Helpers.FormHelpers.field_state(
...> %Phoenix.HTML.Form{
...> source: %{
...> action: :update,
...> changes: %{},
...> errors: [first_name: {"can't be blank", [validation: :required]}],
...> data: nil,
...> valid?: true
...> },
...> },
...> :first_name, nil)
%PrimerLive.FieldState{valid?: false, changeset: %{action: :update, changes: %{}, data: nil, errors: [first_name: {"can't be blank", [validation: :required]}], valid?: true}, message: nil, message_id: nil, field_errors: ["can't be blank"]}
"""
def validation_data(form, field, get_validation_message_fn) do
status = validation_status(form, field, get_validation_message_fn)

{is_error, message, has_message} =
case status do
{:ok, msg} -> {false, msg, !is_nil(msg)}
{:error, msg} -> {true, msg, !is_nil(msg)}
end

validation_message_id = if has_message, do: "#{field}-validation", else: nil

%{
is_error: is_error,
message: message,
has_message: has_message,
validation_message_id: validation_message_id
}
def field_state(form, field, validation_message_fn) do
field_state = get_field_state(form, field, validation_message_fn)

case is_nil(field_state.message) do
true -> field_state
false -> %{field_state | message_id: "#{field}-validation"}
end
end

# Returns an error tuple {:ok, message} or {:error, message}, or nil if no form changeset exists.
# The message is either taken from input attribute `get_validation_message` or from the changeset error message.
defp validation_status(form, field, get_validation_message_fn) do
defp get_field_state(form, field, validation_message_fn) do
changeset = form_changeset(form)
field_state = %PrimerLive.FieldState{}

case is_nil(changeset) do
true ->
{:ok, nil}
field_state

false ->
custom_validation_message =
case is_nil(get_validation_message_fn) do
true -> nil
false -> get_validation_message_fn.(changeset)
field_errors = get_field_errors(changeset, field)
valid? = Enum.count(field_errors) == 0

field_state = %{
field_state
| valid?: valid?,
field_errors: field_errors,
changeset: changeset
}

message =
case is_nil(validation_message_fn) do
true ->
case changeset.action === :validate do
true ->
[field_error | _rest] = field_errors
field_error

false ->
nil
end

false ->
validation_message_fn.(field_state)
end

case is_nil(custom_validation_message) do
true ->
field_errors = field_errors(changeset, field)

case field_errors do
[field_error | _rest] -> {:error, field_error}
_ -> {:ok, nil}
end

false ->
case changeset.valid? do
true -> {:ok, custom_validation_message}
false -> {:error, custom_validation_message}
end
end
%{field_state | message: message}
end
end

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