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[babel-plugin] Support nested objects in defineConsts #1303

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c49b801
Add defineConsts tests
j-malt Oct 31, 2025
f71bfcd
Add defineConsts to the benchmark
j-malt Oct 31, 2025
2957584
Nested consts
j-malt Oct 27, 2025
6f76bef
Update types, tests, use a symbol
j-malt Oct 27, 2025
f1a649c
comment
j-malt Oct 27, 2025
732aabe
Small MDX update
j-malt Oct 27, 2025
cccf3e4
Undo formatting change
j-malt Oct 27, 2025
fe90627
fix flow types
j-malt Oct 29, 2025
a47d513
Evaluate the full path while walking the AST
j-malt Oct 30, 2025
a359ce0
Conflicts should just error
j-malt Oct 30, 2025
286ca2a
Nesting benchmark
j-malt Oct 31, 2025
22ae11c
way less
j-malt Nov 5, 2025
5ce36df
Less example code
j-malt Nov 5, 2025
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9 changes: 9 additions & 0 deletions packages/@stylexjs/babel-plugin/__tests__/__fixtures__/constants.stylex.js
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Original file line number Diff line number Diff line change
Expand Up @@ -21,3 +21,12 @@ export const colors = stylex.defineConsts({
background: 'white',
foreground: 'black',
});

export const nestedTokens = stylex.defineConsts({
button: {
fill: {
primary: 'blue',
},
},
'button.fill.primary': 'red',
});
263 changes: 263 additions & 0 deletions packages/@stylexjs/babel-plugin/__tests__/transform-stylex-defineConsts-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -617,5 +617,268 @@ describe('@stylexjs/babel-plugin', () => {
}
`);
});
test('nested constants object', () => {
const { code, metadata } = transform(`
import * as stylex from '@stylexjs/stylex';
export const tokens = stylex.defineConsts({
button: {
fill: {
primary: 'blue',
secondary: 'gray',
},
},
});
`);

expect(code).toMatchInlineSnapshot(`
"import * as stylex from '@stylexjs/stylex';
export const tokens = {
button: {
fill: {
primary: "blue",
secondary: "gray"
}
}
};"
`);
expect(metadata).toMatchInlineSnapshot(`
{
"stylex": [
[
"xreo3at",
{
"constKey": "xreo3at",
"constVal": "blue",
"ltr": "",
"rtl": null,
},
0,
],
[
"x3rbt3c",
{
"constKey": "x3rbt3c",
"constVal": "gray",
"ltr": "",
"rtl": null,
},
0,
],
],
}
`);
});

test('uses nested constants in stylex.create', () => {
const { code, metadata } = transformWithInlineConsts(`
import * as stylex from '@stylexjs/stylex';
export const tokens = stylex.defineConsts({
button: {
fill: {
primary: 'blue',
},
},
});
export const styles = stylex.create({
root: {
backgroundColor: tokens.button.fill.primary,
},
});
`);

expect(code).toMatchInlineSnapshot(`
"import * as stylex from '@stylexjs/stylex';
export const tokens = {
button: {
fill: {
primary: "blue"
}
}
};
export const styles = {
root: {
kWkggS: "x1t391ir",
$$css: true
}
};"
`);

// Verify const entry and CSS rule with inlined value
expect(metadata).toMatchInlineSnapshot(`
{
"stylex": [
[
"x1wyxh8f",
{
"constKey": "x1wyxh8f",
"constVal": "blue",
"ltr": "",
"rtl": null,
},
0,
],
[
"x1t391ir",
{
"ltr": ".x1t391ir{background-color:blue}",
"rtl": null,
},
3000,
],
],
}
`);
});

test('deeply nested constants', () => {
const { code, metadata } = transform(`
import * as stylex from '@stylexjs/stylex';
export const tokens = stylex.defineConsts({
level1: {
level2: {
level3: {
level4: 'deep-value',
},
},
},
});
`);

expect(code).toMatchInlineSnapshot(`
"import * as stylex from '@stylexjs/stylex';
export const tokens = {
level1: {
level2: {
level3: {
level4: "deep-value"
}
}
}
};"
`);

expect(metadata).toMatchInlineSnapshot(`
{
"stylex": [
[
"x67bk05",
{
"constKey": "x67bk05",
"constVal": "deep-value",
"ltr": "",
"rtl": null,
},
0,
],
],
}
`);
});

test('mixed flat and nested constants', () => {
const { code, metadata } = transform(`
import * as stylex from '@stylexjs/stylex';
export const tokens = stylex.defineConsts({
flatColor: 'red',
nested: {
color: 'blue',
},
});
`);

expect(code).toMatchInlineSnapshot(`
"import * as stylex from '@stylexjs/stylex';
export const tokens = {
flatColor: "red",
nested: {
color: "blue"
}
};"
`);
expect(metadata).toMatchInlineSnapshot(`
{
"stylex": [
[
"x19gcf6u",
{
"constKey": "x19gcf6u",
"constVal": "red",
"ltr": "",
"rtl": null,
},
0,
],
[
"x49cdii",
{
"constKey": "x49cdii",
"constVal": "blue",
"ltr": "",
"rtl": null,
},
0,
],
],
}
`);
});

test('deep chained imported constants work in stylex.create', () => {
const { code, metadata } = transformWithInlineConsts(`
import * as stylex from '@stylexjs/stylex';
import { nestedTokens } from './constants.stylex';
export const styles = stylex.create({
root: {
backgroundColor: nestedTokens.button.fill.primary,
},
});
`);

expect(code).toMatchInlineSnapshot(`
"import * as stylex from '@stylexjs/stylex';
import { nestedTokens } from './constants.stylex';
export const styles = {
root: {
kWkggS: "x13bhmi6",
$$css: true
}
};"
`);

// Should produce a style rule for backgroundColor referencing a CSS variable
// (The const entries themselves are in the metadata of constants.stylex, not this file)
expect(metadata).toMatchInlineSnapshot(`
{
"stylex": [
[
"x13bhmi6",
{
"ltr": ".x13bhmi6{background-color:var(--x529nz8)}",
"rtl": null,
},
3000,
],
],
}
`);
});

test('conflicting nested and flat constant names throws error', () => {
expect(() => {
transform(`
import * as stylex from '@stylexjs/stylex';
export const tokens = stylex.defineConsts({
button: {
fill: {
primary: 'blue',
},
},
'button.fill.primary': 'red',
});
`);
}).toThrow(
/Conflicting constant paths detected: "button\.fill\.primary"/,
);
});
});
});
5 changes: 4 additions & 1 deletion packages/@stylexjs/babel-plugin/src/shared/stylex-consts-utils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,10 @@
* @flow strict
*/

export type ConstsConfigValue = string | number;
export type ConstsConfigValue =
| string
| number
| { [string]: ConstsConfigValue };

export type ConstsConfig = $ReadOnly<{
[string]: ConstsConfigValue,
Expand Down
73 changes: 54 additions & 19 deletions packages/@stylexjs/babel-plugin/src/shared/stylex-define-consts.js
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Original file line number Diff line number Diff line change
Expand Up @@ -15,43 +15,78 @@ import * as messages from './messages';

import createHash from './hash';

type ConstsOutput = string | number | { [string]: ConstsOutput };

export default function styleXDefineConsts<Vars: ConstsConfig>(
constants: Vars,
options: $ReadOnly<{ ...Partial<StyleXOptions>, exportId: string, ... }>,
): [
{ [string]: string | number }, // jsOutput JS output
{ [string]: ConstsOutput }, // jsOutput JS output
{ [string]: InjectableConstStyle }, // metadata for registerinjectableStyles
] {
const { classNamePrefix, exportId, debug, enableDebugClassNames } = {
...defaultOptions,
...options,
};

const jsOutput: { [string]: string | number } = {};
const jsOutput: { [string]: ConstsOutput } = {};
const injectableStyles: { [string]: InjectableConstStyle } = {};
const seenPaths: Set<string> = new Set();

const processEntry = (
key: string,
value: ConstsOutput,
path: Array<string>,
): ConstsOutput => {
if (typeof value === 'object' && value != null) {
const nested: { [string]: ConstsOutput } = {};
for (const [k, v] of Object.entries(value)) {
nested[k] = processEntry(k, v, [...path, k]);
}
return nested;
}

if (typeof value === 'string' || typeof value === 'number') {
const fullPath = path.join('.');

if (seenPaths.has(fullPath)) {
throw new Error(
`Conflicting constant paths detected: "${fullPath}". This can happen when you have both nested properties (e.g., {a: {b: 'value'}}) and a literal dotted key (e.g., {'a.b': 'value'}) that resolve to the same path.`,
);
Comment on lines +53 to +55
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@j-malt j-malt Oct 30, 2025 •
edited
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I couldn't come up with a great way to get around conflicting keys like this and it feels like a pattern to avoid anyways.

}
seenPaths.add(fullPath);

const varSafeKey = path
.map((segment) =>
segment[0] >= '0' && segment[0] <= '9' ? `_${segment}` : segment,
)
.join('_')
.replace(/[^a-zA-Z0-9]/g, '_');

const constKey =
debug && enableDebugClassNames
? `${varSafeKey}-${classNamePrefix}${createHash(`${exportId}.${fullPath}`)}`
: `${classNamePrefix}${createHash(`${exportId}.${fullPath}`)}`;

injectableStyles[constKey] = {
constKey,
constVal: value,
priority: 0,
ltr: '',
rtl: null,
};
return value;
}

return value;
};

for (const [key, value] of Object.entries(constants)) {
if (key.startsWith('--')) {
throw new Error(messages.INVALID_CONST_KEY);
}

const varSafeKey = (
key[0] >= '0' && key[0] <= '9' ? `_${key}` : key
).replace(/[^a-zA-Z0-9]/g, '_');

const constKey =
debug && enableDebugClassNames
? `${varSafeKey}-${classNamePrefix}${createHash(`${exportId}.${key}`)}`
: `${classNamePrefix}${createHash(`${exportId}.${key}`)}`;

jsOutput[key] = value;
injectableStyles[constKey] = {
constKey,
constVal: value,
priority: 0,
ltr: '',
rtl: null,
};
jsOutput[key] = processEntry(key, value, [key]);
}

return [jsOutput, injectableStyles];
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