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merged 3 commits into from
Sep 20, 2024
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chore: refactor set_attributes code generation #13353

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b421ce0
chore: refactor `set_attributes` code generation
Rich-Harris Sep 20, 2024
b3e25e4
simplify
Rich-Harris Sep 20, 2024
ad34112
simplify
Rich-Harris Sep 20, 2024
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160 changes: 45 additions & 115 deletions packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,8 @@ import {
get_attribute_name,
build_attribute_value,
build_class_directives,
build_style_directives
build_style_directives,
build_set_attributes
} from './shared/element.js';
import { process_children } from './shared/fragment.js';
import {
Expand Down Expand Up @@ -95,7 +96,7 @@ export function RegularElement(node, context) {
/** @type {Map<string, AST.BindDirective>} */
const bindings = new Map();

let has_spread = false;
let has_spread = node.metadata.has_spread;
let has_use = false;

for (const attribute of node.attributes) {
Expand All @@ -105,6 +106,16 @@ export function RegularElement(node, context) {
break;

case 'Attribute':
// `is` attributes need to be part of the template, otherwise they break
if (attribute.name === 'is' && context.state.metadata.namespace === 'html') {
const { value } = build_attribute_value(attribute.value, context);

if (value.type === 'Literal' && typeof value.value === 'string') {
context.state.template.push(` is="${escape_html(value.value, true)}"`);
continue;
}
}

attributes.push(attribute);
lookup.set(attribute.name, attribute);
break;
Expand All @@ -129,7 +140,6 @@ export function RegularElement(node, context) {

case 'SpreadAttribute':
attributes.push(attribute);
has_spread = true;
break;

case 'StyleDirective':
Expand Down Expand Up @@ -194,17 +204,40 @@ export function RegularElement(node, context) {
const node_id = context.state.node;

// Then do attributes
let is_attributes_reactive = false;
if (node.metadata.has_spread) {
build_element_spread_attributes(
let is_attributes_reactive = has_spread;

if (has_spread) {
const attributes_id = b.id(context.state.scope.generate('attributes'));

build_set_attributes(
attributes,
context,
node,
node_id,
// If value binding exists, that one takes care of calling $.init_select
node.name === 'select' && !bindings.has('value')
attributes_id,
(node.metadata.svg || node.metadata.mathml || is_custom_element_node(node)) && b.true,
node.name.includes('-') && b.true
);
is_attributes_reactive = true;

// If value binding exists, that one takes care of calling $.init_select
if (node.name === 'select' && !bindings.has('value')) {
context.state.init.push(
b.stmt(b.call('$.init_select', node_id, b.thunk(b.member(attributes_id, 'value'))))
);

context.state.update.push(
b.if(
b.binary('in', b.literal('value'), attributes_id),
b.block([
// This ensures a one-way street to the DOM in case it's <select {value}>
// and not <select bind:value>. We need it in addition to $.init_select
// because the select value is not reflected as an attribute, so the
// mutation observer wouldn't notice.
b.stmt(b.call('$.select_option', node_id, b.member(attributes_id, 'value')))
])
)
);
}
} else {
/** If true, needs `__value` for inputs */
const needs_special_value_handling =
Expand All @@ -229,7 +262,7 @@ export function RegularElement(node, context) {
attribute.name !== 'autofocus' &&
(attribute.value === true || is_text_attribute(attribute))
) {
const name = get_attribute_name(node, attribute, context);
const name = get_attribute_name(node, attribute);
const value = is_text_attribute(attribute) ? attribute.value[0].data : true;

if (name !== 'class' || value) {
Expand Down Expand Up @@ -258,7 +291,7 @@ export function RegularElement(node, context) {
node_id,
context,
is_attributes_reactive,
lookup.has('style') || node.metadata.has_spread
lookup.has('style') || has_spread
);

// Apply the src and loading attributes for <img> elements after the element is appended to the document
Expand Down Expand Up @@ -448,109 +481,6 @@ function setup_select_synchronization(value_binding, context) {
);
}

/**
* @param {Array<AST.Attribute | AST.SpreadAttribute>} attributes
* @param {ComponentContext} context
* @param {AST.RegularElement} element
* @param {Identifier} element_id
* @param {boolean} needs_select_handling
*/
function build_element_spread_attributes(
attributes,
context,
element,
element_id,
needs_select_handling
) {
let needs_isolation = false;

/** @type {ObjectExpression['properties']} */
const values = [];

for (const attribute of attributes) {
if (attribute.type === 'Attribute') {
const name = get_attribute_name(element, attribute, context);
// TODO: handle has_call
const { value } = build_attribute_value(attribute.value, context);

if (
name === 'is' &&
value.type === 'Literal' &&
context.state.metadata.namespace === 'html'
) {
context.state.template.push(` is="${escape_html(value.value, true)}"`);
continue;
}

if (
is_event_attribute(attribute) &&
(get_attribute_expression(attribute).type === 'ArrowFunctionExpression' ||
get_attribute_expression(attribute).type === 'FunctionExpression')
) {
// Give the event handler a stable ID so it isn't removed and readded on every update
const id = context.state.scope.generate('event_handler');
context.state.init.push(b.var(id, value));
values.push(b.init(attribute.name, b.id(id)));
} else {
values.push(b.init(name, value));
}
} else {
values.push(b.spread(/** @type {Expression} */ (context.visit(attribute))));
}

needs_isolation ||=
attribute.type === 'SpreadAttribute' && attribute.metadata.expression.has_call;
}

const preserve_attribute_case =
element.metadata.svg || element.metadata.mathml || is_custom_element_node(element);
const id = b.id(context.state.scope.generate('attributes'));

const update = b.stmt(
b.assignment(
'=',
id,
b.call(
'$.set_attributes',
element_id,
id,
b.object(values),
context.state.analysis.css.hash !== '' && b.literal(context.state.analysis.css.hash),
preserve_attribute_case && b.true,
is_ignored(element, 'hydration_attribute_changed') && b.true,
element.name.includes('-') && b.true
)
)
);

context.state.init.push(b.let(id));

// objects could contain reactive getters -> play it safe and always assume spread attributes are reactive
if (needs_isolation) {
context.state.init.push(build_update(update));
} else {
context.state.update.push(update);
}

if (needs_select_handling) {
context.state.init.push(
b.stmt(b.call('$.init_select', element_id, b.thunk(b.member(id, 'value'))))
);
context.state.update.push(
b.if(
b.binary('in', b.literal('value'), id),
b.block([
// This ensures a one-way street to the DOM in case it's <select {value}>
// and not <select bind:value>. We need it in addition to $.init_select
// because the select value is not reflected as an attribute, so the
// mutation observer wouldn't notice.
b.stmt(b.call('$.select_option', element_id, b.member(id, 'value')))
])
)
);
}
}

/**
* Serializes an assignment to an element property by adding relevant statements to either only
* the init or the the init and update arrays, depending on whether or not the value is dynamic.
Expand Down Expand Up @@ -581,7 +511,7 @@ function build_element_spread_attributes(
*/
function build_element_attribute_update_assignment(element, node_id, attribute, context) {
const state = context.state;
const name = get_attribute_name(element, attribute, context);
const name = get_attribute_name(element, attribute);
const is_svg = context.state.metadata.namespace === 'svg' || element.name === 'svg';
const is_mathml = context.state.metadata.namespace === 'mathml';
let { has_call, value } = build_attribute_value(attribute.value, context);
Expand Down
130 changes: 24 additions & 106 deletions packages/svelte/src/compiler/phases/3-transform/client/visitors/SvelteElement.js
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ import { determine_namespace_for_children } from '../../utils.js';
import {
build_attribute_value,
build_class_directives,
build_set_attributes,
build_style_directives
} from './shared/element.js';
import { build_render_statement, build_update } from './shared/utils.js';
Expand Down Expand Up @@ -81,10 +82,29 @@ export function SvelteElement(node, context) {
context.state.init.push(...lets); // create computeds in the outer context; the dynamic element is the single child of this slot

// Then do attributes
// Always use spread because we don't know whether the element is a custom element or not,
// therefore we need to do the "how to set an attribute" logic at runtime.
const is_attributes_reactive =
build_dynamic_element_attributes(node, attributes, inner_context, element_id) !== null;
let is_attributes_reactive = false;

if (attributes.length === 0) {
if (context.state.analysis.css.hash) {
inner_context.state.init.push(
b.stmt(b.call('$.set_class', element_id, b.literal(context.state.analysis.css.hash)))
);
}
} else {
const attributes_id = b.id(context.state.scope.generate('attributes'));

// Always use spread because we don't know whether the element is a custom element or not,
// therefore we need to do the "how to set an attribute" logic at runtime.
is_attributes_reactive = build_set_attributes(
attributes,
inner_context,
node,
element_id,
attributes_id,
b.binary('!==', b.member(element_id, 'namespaceURI'), b.id('$.NAMESPACE_SVG')),
b.call(b.member(b.member(element_id, 'nodeName'), 'includes'), b.literal('-'))
);
}

// class/style directives must be applied last since they could override class/style attributes
build_class_directives(class_directives, element_id, inner_context, is_attributes_reactive);
Expand Down Expand Up @@ -133,105 +153,3 @@ export function SvelteElement(node, context) {
)
);
}

/**
* Serializes dynamic element attribute assignments.
* Returns the `true` if spread is deemed reactive.
* @param {AST.SvelteElement} element
* @param {Array<AST.Attribute | AST.SpreadAttribute>} attributes
* @param {ComponentContext} context
* @param {Identifier} element_id
* @returns {boolean}
*/
function build_dynamic_element_attributes(element, attributes, context, element_id) {
if (attributes.length === 0) {
if (context.state.analysis.css.hash) {
context.state.init.push(
b.stmt(b.call('$.set_class', element_id, b.literal(context.state.analysis.css.hash)))
);
}
return false;
}

// TODO why are we always treating this as a spread? needs docs, if that's not an error

let needs_isolation = false;
let is_reactive = false;

/** @type {ObjectExpression['properties']} */
const values = [];

for (const attribute of attributes) {
if (attribute.type === 'Attribute') {
const { value } = build_attribute_value(attribute.value, context);

if (
is_event_attribute(attribute) &&
(get_attribute_expression(attribute).type === 'ArrowFunctionExpression' ||
get_attribute_expression(attribute).type === 'FunctionExpression')
) {
// Give the event handler a stable ID so it isn't removed and readded on every update
const id = context.state.scope.generate('event_handler');
context.state.init.push(b.var(id, value));
values.push(b.init(attribute.name, b.id(id)));
} else {
values.push(b.init(attribute.name, value));
}
} else {
values.push(b.spread(/** @type {Expression} */ (context.visit(attribute))));
}

is_reactive ||=
attribute.metadata.expression.has_state ||
// objects could contain reactive getters -> play it safe and always assume spread attributes are reactive
attribute.type === 'SpreadAttribute';
needs_isolation ||=
attribute.type === 'SpreadAttribute' && attribute.metadata.expression.has_call;
}

if (needs_isolation || is_reactive) {
const id = context.state.scope.generate('attributes');
context.state.init.push(b.let(id));

const update = b.stmt(
b.assignment(
'=',
b.id(id),
b.call(
'$.set_attributes',
element_id,
b.id(id),
b.object(values),
context.state.analysis.css.hash !== '' && b.literal(context.state.analysis.css.hash),
b.binary('!==', b.member(element_id, 'namespaceURI'), b.id('$.NAMESPACE_SVG')),
is_ignored(element, 'hydration_attribute_changed') && b.true,
b.call(b.member(b.member(element_id, 'nodeName'), 'includes'), b.literal('-'))
)
)
);

if (needs_isolation) {
context.state.init.push(build_update(update));
return false;
}

context.state.update.push(update);
return true;
}

context.state.init.push(
b.stmt(
b.call(
'$.set_attributes',
element_id,
b.literal(null),
b.object(values),
context.state.analysis.css.hash !== '' && b.literal(context.state.analysis.css.hash),
b.binary('!==', b.member(element_id, 'namespaceURI'), b.id('$.NAMESPACE_SVG')),
is_ignored(element, 'hydration_attribute_changed') && b.true,
b.call(b.member(b.member(element_id, 'nodeName'), 'includes'), b.literal('-'))
)
)
);
return false;
}
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