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Fix array minItems/maxItems bugs #2546

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Fix array minItems/maxItems bugs #2546

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c074cdd
fix(openapi-typescript): fix array minItems/maxItems tuple generation…
simonsolnes Dec 10, 2025
2c1266e
fix(openapi-typescript): fix nested array nesting with --array-length…
simonsolnes Dec 10, 2025
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18 changes: 6 additions & 12 deletions packages/openapi-typescript/src/transform/schema-object.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -346,18 +346,16 @@ function transformSchemaObjectCore(schemaObject: SchemaObject, options: Transfor
if (schemaObject.type === "array") {
// default to `unknown[]`
let itemType: ts.TypeNode = UNKNOWN;
let isTupleType = false;
// tuple type
if (schemaObject.prefixItems || Array.isArray(schemaObject.items)) {
const prefixItems = schemaObject.prefixItems ?? (schemaObject.items as (SchemaObject | ReferenceObject)[]);
itemType = ts.factory.createTupleTypeNode(prefixItems.map((item) => transformSchemaObject(item, options)));
isTupleType = true;
}
// standard array type
else if (schemaObject.items) {
if (hasKey(schemaObject.items, "type") && schemaObject.items.type === "array") {
itemType = ts.factory.createArrayTypeNode(transformSchemaObject(schemaObject.items, options));
} else {
itemType = transformSchemaObject(schemaObject.items, options);
}
itemType = transformSchemaObject(schemaObject.items, options);
}

const min: number =
Expand All @@ -381,10 +379,9 @@ function transformSchemaObjectCore(schemaObject: SchemaObject, options: Transfor
} else if ((schemaObject.maxItems as number) > 0) {
// if maxItems is set, then return a union of all permutations of possible tuple types
const members: ts.TypeNode[] = [];
// populate 1 short of min …
for (let i = 0; i <= (max ?? 0) - min; i++) {
for (let i = min; i <= (max ?? 0); i++) {
const elements: ts.TypeNode[] = [];
for (let j = min; j < i + min; j++) {
for (let j = 0; j < i; j++) {
elements.push(itemType);
}
members.push(ts.factory.createTupleTypeNode(elements));
Expand All @@ -402,10 +399,7 @@ function transformSchemaObjectCore(schemaObject: SchemaObject, options: Transfor
}
}

const finalType =
ts.isTupleTypeNode(itemType) || ts.isArrayTypeNode(itemType)
? itemType
: ts.factory.createArrayTypeNode(itemType); // wrap itemType in array type, but only if not a tuple or array already
const finalType = isTupleType ? itemType : ts.factory.createArrayTypeNode(itemType);

return options.ctx.immutable
? ts.factory.createTypeOperatorNode(ts.SyntaxKind.ReadonlyKeyword, finalType)
Expand Down
302 changes: 302 additions & 0 deletions packages/openapi-typescript/test/transform/schema-object/array.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -168,6 +168,308 @@ describe("transformSchemaObject > array", () => {
},
},
],
[
"options > arrayLength: true > minItems: 1, maxItems: 3",
{
given: { type: "array", items: { type: "string" }, minItems: 1, maxItems: 3 },
want: `[
string
] | [
string,
string
] | [
string,
string,
string
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > minItems: 0, maxItems: 2 (starts from empty)",
{
given: { type: "array", items: { type: "string" }, minItems: 0, maxItems: 2 },
want: `[
] | [
string
] | [
string,
string
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > minItems: 3, maxItems: 5 (larger range)",
{
given: { type: "array", items: { type: "number" }, minItems: 3, maxItems: 5 },
want: `[
number,
number,
number
] | [
number,
number,
number,
number
] | [
number,
number,
number,
number,
number
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > minItems: 2, maxItems: 3 with object items",
{
given: {
type: "array",
items: { type: "object", properties: { id: { type: "string" } } },
minItems: 2,
maxItems: 3,
},
want: `[
{
id?: string;
},
{
id?: string;
}
] | [
{
id?: string;
},
{
id?: string;
},
{
id?: string;
}
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > nested array with minItems equals maxItems",
{
given: {
type: "array",
items: { type: "array", items: { type: "string" } },
minItems: 2,
maxItems: 2,
},
want: `[
string[],
string[]
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > nested array with inner minItems equals maxItems",
{
given: {
type: "array",
items: {
type: "array",
items: { type: "string" },
minItems: 3,
maxItems: 3,
},
},
want: `[
string,
string,
string
][]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > triple nested array",
{
given: {
type: "array",
items: {
type: "array",
items: { type: "array", items: { type: "string" } },
},
},
want: "string[][][]",
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > nested array with both inner and outer constraints",
{
given: {
type: "array",
items: {
type: "array",
items: { type: "boolean" },
minItems: 2,
maxItems: 2,
},
minItems: 3,
maxItems: 3,
},
want: `[
[
boolean,
boolean
],
[
boolean,
boolean
],
[
boolean,
boolean
]
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > nested array without constraints",
{
given: {
type: "array",
items: { type: "array", items: { type: "number" } },
},
want: "number[][]",
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > nested tuple (prefixItems) in array",
{
given: {
type: "array",
items: {
type: "array",
prefixItems: [{ type: "string" }, { type: "number" }],
},
minItems: 2,
maxItems: 2,
},
want: `[
[
string,
number
],
[
string,
number
]
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > nested array with minItems: 0, maxItems: 2",
{
given: {
type: "array",
items: { type: "array", items: { type: "string" } },
minItems: 0,
maxItems: 2,
},
want: `[
] | [
string[]
] | [
string[],
string[]
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > deeply nested with constraints at multiple levels",
{
given: {
type: "array",
items: {
type: "array",
items: {
type: "array",
items: { type: "number" },
minItems: 2,
maxItems: 2,
},
},
minItems: 1,
maxItems: 1,
},
want: `[
[
number,
number
][]
]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > arrayLength: true > array of tuples without outer constraints",
{
given: {
type: "array",
items: {
type: "array",
prefixItems: [{ type: "string" }, { type: "boolean" }],
},
},
want: `[
string,
boolean
][]`,
options: {
...DEFAULT_OPTIONS,
ctx: { ...DEFAULT_OPTIONS.ctx, arrayLength: true },
},
},
],
[
"options > immutable: true",
{
Expand Down