Sourcing

What to order for each part: MPN and MPN:<tag> keys on parts, sourcing tags on boards and fab targets, and the BOM they resolve to. Write part numbers inline or in a separate <board>.sourcing.ts module of source() calls.

Keys

• MPN is the catch-all part number.
• MPN:<tag> is the part number for one named source, such as MPN:LCSC, MPN:DigiKey, MPN:Mouser, MPN:US or MPN:CN. Tags are free strings compared without case.
• Every other key, such as Manufacturer, Datasheet or Description, is a plain BOM field.
• The keys are typed as SourcingSpec, so the editor completes them.

Inline

The spec is the second argument of a factory, the source option, or a .source() call:

export const Q1 = SOT23(3)('MMBT3904', { MPN: 'MMBT3904LT1G', Manufacturer: 'onsemi' }).connect(SIG, GND, SW)
export const R1 = R0603('330', { MPN: 'RC0603FR-07330RL', 'MPN:LCSC': 'C23138' }).connect(VCC, LED1)
export const R2 = R0603({ value: '330', source: { MPN: 'RC0603FR-07330RL' } }).source({ 'MPN:LCSC': 'C23138' }).connect(VCC, LED2)

Out of line

source() from @pcbjs/core sets keys from any module the entry imports:

// blinky.sourcing.ts, imported by blinky.pcb.tsx with import './blinky.sourcing'
import { source } from '@pcbjs/core'
import { R0603 } from '@pcbjs/lib'
import { J1, C1 } from './blinky.sch'

source(R0603, '330', { MPN: 'RC0603FR-07330RL', 'MPN:LCSC': 'C23138' })   // every R0603 with value 330
source(C1, { MPN: 'CL10B104KB8NNNC', 'MPN:LCSC': 'C14663' })              // one part, an instance, or an array
source(J1, { MPN: 'PEC03SAAN', Manufacturer: 'Sullins' })

The keys merge at compile time, lowest first, a later key replacing an earlier one:

1. source(factory, value, spec) rules, in call order.
2. source(part, spec) calls, in call order.
3. The part options: fields, then source or the second argument.
4. .source() calls on the part.
5. The fields of the placement, <R1 at="12 5" fields={{ … }} />.

A factory rule reaches only boards whose entry imports the module that made it. Plain footprints take the same keys through fields.

Tags on the board

A board or fab target carries an ordered list of tags, sourcing on <PCB>. It resolves like every board setting: [] at the base, then defineDefaultBoard, then the preset or target, then the prop.

Fab preset	Tags
JLCPCB	['LCSC', 'CN']
PCBWay	['CN']
OSH Park	['DigiKey', 'US']
Eurocircuits	['Mouser', 'EU']
Advanced PCB	['DigiKey', 'US']

Each BOM row resolves to the first MPN:<tag> it has in tag order, else its MPN, else nothing. With variants(JLCPCB, OSHPark, { name: 'House' }) a resistor orders its LCSC code from JLCPCB, its DigiKey or US number from OSH Park and its MPN from House. A plain target sets tags with sourcing: ['US'].

Checks and outputs

• The rule requireSourcing: true makes a BOM row without any part number the ERC warning unsourced-part.
• A row whose only keys are tags the board does not list is the ERC warning unsourced-target, whenever the board has tags.
• bom.csv gets the resolved number in MPN and the matched tag in Source, see fab-set.md.
• README-fab has a line such as Sourcing: tags LCSC, CN; 3 rows, 0 without a part number.
• resolveSourcing(fields, tags) from @pcbjs/core returns { mpn, tag, all, manufacturer?, datasheet? } for any fields. tag is "" for the catch-all and null when nothing matched.