preset.js

// Custom graphql-codegen preset: one output file per source .graphql file.
//
// app/notes.graphql        -> app/notes.graphql.ts        (typed operation wrapper)
// note/card/note.graphql   -> note/card/note.graphql.ts   (fragment type + unmask helper)
// plus one shared graphql/schema.graphql.ts (scalars, enums, input types).
//
// Each output is wrapped in `namespace $` - the $mol builder compiles it as an
// ordinary module .ts, no builder changes ("two builders through a file seam").
const path = require('path')

const addPlugin = require('@graphql-codegen/add')
const molPlugin = require('./molplugin.js')

const HEADER = '// AUTO-GENERATED by `npm run codegen` - do not edit.\n'

// $-symbol for a file: note/card/note.graphql + package `demo` -> $demo_note_card_note
// (the repo is one mam PACKAGE; symbols are workspace-rooted, hence the prefix)
function fileSymbol(location, pack) {
	const rel = path.relative(process.cwd(), location).replace(/\.graphql$/, '')
	const segs = [...(pack ? pack.split('/') : []), ...rel.split(path.sep)]
	return '$' + segs.join('_').replace(/[^a-zA-Z0-9_]/g, '_')
}

module.exports = {
	buildGeneratesSection: options => {
		const config = options.config || {}
		const pack = config.molPackage || ''
		const runtime = config.molRuntime || '$graphql'
		// molSchemaTypes: false skips the shared types file (a secondary output
		// reusing the one another output already generates, e.g. test fixtures)
		const schemaTypesFile = config.molSchemaTypes === false ? null : config.molSchemaTypes || 'graphql/schema.graphql.ts'

		const pluginMap = {
			add: addPlugin,
			mol: molPlugin,
		}

		// Registry of all named fragments across every .graphql file.
		// Fragments are global: any operation may spread any fragment by its
		// (globally unique) name - no tie to the component tree.
		const fragments = {}
		for (const doc of options.documents) {
			for (const def of doc.document.definitions) {
				if (def.kind !== 'FragmentDefinition') continue
				const name = def.name.value
				if (fragments[name]) {
					throw new Error(
						`Duplicate fragment name "${name}" in ${doc.location} and ${fragments[name].location}. ` +
						`Fragment names must be globally unique - name each after its file path ` +
						`(a/b/c.graphql -> a_b_c), which cannot collide.`,
					)
				}
				fragments[name] = {
					location: doc.location,
					symbol: fileSymbol(doc.location, pack),
					node: def,
					source: (doc.rawSDL || '').trim(),
					spreads: collectSpreads(def),
				}
			}
		}

		const outputs = []

		for (const doc of options.documents) {
			const defs = doc.document.definitions.filter(
				def => def.kind === 'OperationDefinition' || def.kind === 'FragmentDefinition',
			)
			if (defs.length !== 1) {
				throw new Error(
					`${doc.location}: expected exactly one operation or fragment per .graphql file, found ${defs.length}`,
				)
			}

			// fragments defined in OTHER files: typescript-operations must know
			// them to type spreads, but must not re-emit their types here
			const external = Object.values(fragments)
				.filter(frag => frag.location !== doc.location)
				.map(frag => ({
					name: frag.node.name.value,
					onType: frag.node.typeCondition.name.value,
					node: frag.node,
					isExternal: true,
					importFrom: null,
				}))

			outputs.push({
				filename: doc.location + '.ts',
				schema: options.schema,
				schemaAst: options.schemaAst,
				documents: [doc],
				pluginMap,
				plugins: [
					{ add: { placement: 'prepend', content: HEADER + 'namespace $ {\n' } },
					{ mol: {} },
					{ add: { placement: 'append', content: '\n}\n' } },
				],
				config: {
					...config,
					externalFragments: external,
					molSymbol: fileSymbol(doc.location, pack),
					molRuntime: runtime,
					molFragments: fragments,
				},
			})
		}

		// shared schema-level types (Scalars, Maybe, Exact, enums, inputs) -
		// one file, same `namespace $`, referenced by all generated files
		if (schemaTypesFile) outputs.push({
			filename: schemaTypesFile,
			schema: options.schema,
			schemaAst: options.schemaAst,
			documents: [],
			pluginMap,
			plugins: [
				{ add: { placement: 'prepend', content: HEADER + 'namespace $ {\n' } },
				{ mol: {} },
				{ add: { placement: 'append', content: '\n}\n' } },
			],
			config: { ...config, molMode: 'schema' },
		})

		return outputs
	},
}

function collectSpreads(node, acc = new Set()) {
	if (node.kind === 'FragmentSpread') acc.add(node.name.value)
	for (const key of ['selectionSet', 'selections']) {
		const sub = node[key]
		if (Array.isArray(sub)) sub.forEach(child => collectSpreads(child, acc))
		else if (sub && typeof sub === 'object') collectSpreads(sub, acc)
	}
	return acc
}