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Support a best approximation of if/then/else (#26)
Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>
1 parent 6c8870e commit 700dc70

16 files changed

Lines changed: 360 additions & 43 deletions

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‎README.markdown‎

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Original file line numberDiff line numberDiff line change
@@ -39,9 +39,9 @@ to use a JSON Schema validator at runtime to enforce remaining constraints.
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| Applicator (2020-12) | `allOf` | Yes |
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| Applicator (2020-12) | `oneOf` | **PARTIAL GIVEN LANGUAGE LIMITATIONS** |
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| Applicator (2020-12) | `not` | **CANNOT SUPPORT** |
42-
| Applicator (2020-12) | `if` | Pending |
43-
| Applicator (2020-12) | `then` | Pending |
44-
| Applicator (2020-12) | `else` | Pending |
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| Applicator (2020-12) | `if` | **PARTIAL GIVEN LANGUAGE LIMITATIONS** |
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| Applicator (2020-12) | `then` | **PARTIAL GIVEN LANGUAGE LIMITATIONS** |
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| Applicator (2020-12) | `else` | **PARTIAL GIVEN LANGUAGE LIMITATIONS** |
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| Validation (2020-12) | `type` | Yes |
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| Validation (2020-12) | `enum` | Yes |
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| Validation (2020-12) | `required` | Yes |

‎src/generator/include/sourcemeta/codegen/generator_typescript.h‎

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@@ -30,6 +30,7 @@ class SOURCEMETA_CODEGEN_GENERATOR_EXPORT TypeScript {
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auto operator()(const IRTuple &entry) -> void;
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auto operator()(const IRUnion &entry) -> void;
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auto operator()(const IRIntersection &entry) -> void;
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auto operator()(const IRConditional &entry) -> void;
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private:
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// Exporting symbols that depends on the standard C++ library is considered

‎src/generator/typescript.cc‎

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@@ -303,4 +303,26 @@ auto TypeScript::operator()(const IRIntersection &entry) -> void {
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this->output << ";\n";
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}
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auto TypeScript::operator()(const IRConditional &entry) -> void {
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// As a notable limitation, TypeScript cannot express the negation of an
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// if/then/else condition, so the else branch is wider than what JSON
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// Schema allows
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this->output << "// (if & then) | else approximation: the else branch is "
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"wider than what\n";
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this->output << "// JSON Schema allows, as TypeScript cannot express type "
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"negation\n";
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this->output << "export type "
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<< mangle(this->prefix, entry.pointer, entry.symbol, this->cache)
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<< " =\n ("
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<< mangle(this->prefix, entry.condition.pointer,
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entry.condition.symbol, this->cache)
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<< " & "
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<< mangle(this->prefix, entry.consequent.pointer,
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entry.consequent.symbol, this->cache)
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<< ") | "
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<< mangle(this->prefix, entry.alternative.pointer,
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entry.alternative.symbol, this->cache)
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<< ";\n";
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}
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} // namespace sourcemeta::codegen

‎src/ir/include/sourcemeta/codegen/ir.h‎

Lines changed: 10 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -97,15 +97,22 @@ struct IRImpossible : IRType {};
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/// @ingroup ir
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struct IRAny : IRType {};
9999

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/// @ingroup ir
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struct IRConditional : IRType {
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IRType condition;
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IRType consequent;
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IRType alternative;
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};
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/// @ingroup ir
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struct IRReference : IRType {
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IRType target;
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};
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/// @ingroup ir
106-
using IREntity =
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std::variant<IRObject, IRScalar, IREnumeration, IRUnion, IRIntersection,
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IRArray, IRTuple, IRImpossible, IRAny, IRReference>;
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using IREntity = std::variant<IRObject, IRScalar, IREnumeration, IRUnion,
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IRIntersection, IRConditional, IRArray, IRTuple,
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IRImpossible, IRAny, IRReference>;
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/// @ingroup ir
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using IRResult = std::vector<IREntity>;

‎src/ir/ir_default_compiler.h‎

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Original file line numberDiff line numberDiff line change
@@ -612,6 +612,53 @@ auto handle_allof(const sourcemeta::core::JSON &schema,
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std::move(branches)};
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}
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auto handle_if_then_else(
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const sourcemeta::core::JSON &schema,
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const sourcemeta::core::SchemaFrame &frame,
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const sourcemeta::core::SchemaFrame::Location &location,
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const sourcemeta::core::Vocabularies &,
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const sourcemeta::core::SchemaResolver &,
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const sourcemeta::core::JSON &subschema) -> IREntity {
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ONLY_WHITELIST_KEYWORDS(schema, subschema, location.pointer,
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{"$schema", "$id", "$anchor", "$dynamicAnchor",
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"$defs", "$vocabulary", "if", "then", "else",
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"title", "description", "default", "deprecated",
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"readOnly", "writeOnly", "examples",
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"unevaluatedProperties", "unevaluatedItems"});
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629+
assert(subschema.defines("if"));
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assert(subschema.defines("then"));
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assert(subschema.defines("else"));
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auto if_pointer{sourcemeta::core::to_pointer(location.pointer)};
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if_pointer.push_back("if");
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const auto if_location{
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frame.traverse(sourcemeta::core::to_weak_pointer(if_pointer))};
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assert(if_location.has_value());
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639+
auto then_pointer{sourcemeta::core::to_pointer(location.pointer)};
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then_pointer.push_back("then");
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const auto then_location{
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frame.traverse(sourcemeta::core::to_weak_pointer(then_pointer))};
643+
assert(then_location.has_value());
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645+
auto else_pointer{sourcemeta::core::to_pointer(location.pointer)};
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else_pointer.push_back("else");
647+
const auto else_location{
648+
frame.traverse(sourcemeta::core::to_weak_pointer(else_pointer))};
649+
assert(else_location.has_value());
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651+
return IRConditional{
652+
{.pointer = sourcemeta::core::to_pointer(location.pointer),
653+
.symbol = symbol(frame, location)},
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{.pointer = std::move(if_pointer),
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.symbol = symbol(frame, if_location.value().get())},
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{.pointer = std::move(then_pointer),
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.symbol = symbol(frame, then_location.value().get())},
658+
{.pointer = std::move(else_pointer),
659+
.symbol = symbol(frame, else_location.value().get())}};
660+
}
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615662
auto default_compiler(const sourcemeta::core::JSON &schema,
616663
const sourcemeta::core::SchemaFrame &frame,
617664
const sourcemeta::core::SchemaFrame::Location &location,
@@ -704,8 +751,8 @@ auto default_compiler(const sourcemeta::core::JSON &schema,
704751
return handle_ref(schema, frame, location, vocabularies, resolver,
705752
subschema);
706753
} else if (subschema.defines("if")) {
707-
throw UnsupportedKeywordError(schema, location.pointer, "if",
708-
"Unsupported keyword in subschema");
754+
return handle_if_then_else(schema, frame, location, vocabularies, resolver,
755+
subschema);
709756
} else if (subschema.defines("not")) {
710757
throw UnsupportedKeywordError(schema, location.pointer, "not",
711758
"Unsupported keyword in subschema");

‎test/e2e/typescript/2020-12/if_then_else_objects/expected.d.ts‎

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@@ -0,0 +1,25 @@
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export type ShapeThenRadius = number;
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export interface ShapeThen {
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"radius": ShapeThenRadius;
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[key: string]: unknown | undefined;
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}
7+
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export type ShapeIfKind = "circle";
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export interface ShapeIf {
11+
"kind": ShapeIfKind;
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[key: string]: unknown | undefined;
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}
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15+
export type ShapeElseSides = number;
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17+
export interface ShapeElse {
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"sides": ShapeElseSides;
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[key: string]: unknown | undefined;
20+
}
21+
22+
// (if & then) | else approximation: the else branch is wider than what
23+
// JSON Schema allows, as TypeScript cannot express type negation
24+
export type Shape =
25+
(ShapeIf & ShapeThen) | ShapeElse;

‎test/e2e/typescript/2020-12/if_then_else_objects/options.json‎

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@@ -0,0 +1,3 @@
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{
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"defaultPrefix": "Shape"
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}

‎test/e2e/typescript/2020-12/if_then_else_objects/schema.json‎

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@@ -0,0 +1,18 @@
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{
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"$schema": "https://json-schema.org/draft/2020-12/schema",
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"if": {
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"type": "object",
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"properties": { "kind": { "const": "circle" } },
6+
"required": [ "kind" ]
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},
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"then": {
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"type": "object",
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"properties": { "radius": { "type": "number" } },
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"required": [ "radius" ]
12+
},
13+
"else": {
14+
"type": "object",
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"properties": { "sides": { "type": "integer" } },
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"required": [ "sides" ]
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}
18+
}

‎test/e2e/typescript/2020-12/if_then_else_objects/test.ts‎

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@@ -0,0 +1,31 @@
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import { Shape } from "./expected";
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3+
// Valid: satisfies the if condition (kind="circle") and then branch (radius)
4+
const circle: Shape = {
5+
kind: "circle",
6+
radius: 5
7+
};
8+
9+
// Valid: does not satisfy the if condition, satisfies else branch (sides)
10+
const polygon: Shape = {
11+
sides: 6
12+
};
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14+
// Invalid: satisfies if (kind="circle") but missing then's required radius
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// @ts-expect-error
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const circleWithoutRadius: Shape = {
17+
kind: "circle"
18+
};
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20+
// Invalid: does not satisfy if, and missing else's required sides
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// @ts-expect-error
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const emptyObject: Shape = {};
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24+
// NOTE: This passes TypeScript but would fail JSON Schema validation.
25+
// The if condition matches (kind is "circle"), so the then branch should
26+
// apply (requiring radius). But our (If & Then) | Else approximation
27+
// allows the else branch to also match when if holds.
28+
const circleMatchingElse: Shape = {
29+
kind: "circle",
30+
sides: 4
31+
};

‎test/e2e/typescript/2020-12/if_then_else_validation_only/expected.d.ts‎

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@@ -0,0 +1,16 @@
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export type PatternString_1 = string;
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export type PatternString_0Then = string;
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export type PatternString_0If = string;
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7+
export type PatternString_0Else = string;
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// (if & then) | else approximation: the else branch is wider than what
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// JSON Schema allows, as TypeScript cannot express type negation
11+
export type PatternString_0 =
12+
(PatternString_0If & PatternString_0Then) | PatternString_0Else;
13+
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export type PatternString =
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PatternString_0 &
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PatternString_1;

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