OliverJAsh · May 7, 2020 17:06
diff --git a/foo.ts b/foo.ts
 import * as Reader from 'fp-ts/lib/Reader';
 import { RouteData } from 'helpers/routes/types';
 import { pipe, pipeWith } from 'pipe-ts';

 // This will soon be part of fp-ts core
 // https://github.com/gcanti/fp-ts/issues/904#issuecomment-619346296
 const chainW: <Q, A, B>(
  f: (a: A) => Reader.Reader<Q, B>,
 ) => <R>(ma: Reader.Reader<R, A>) => Reader.Reader<R & Q, B> = Reader.chain as Unrestricted;

 {
  const renderCopyright = RouteData.match({
    Search: () => 'unsplash search copyright goes here',
    default: () => 'unsplash copyright goes here',
  });

  // ✅ doesn't care about child deps (routeData)
  const renderFooter = (year: number) =>
    pipe(renderCopyright, copyright => `<footer>${copyright} ${year}</footer>`);

  // ❌ does care about child deps (year)
  const renderPage = (hideFooter: boolean) => ({ year }: { year: number }) => {
    if (hideFooter) {
      return () => '<body>No Footer.</body>';
    } else {
      return pipe(renderFooter(year), footer => `<body>${footer}</body>`);
    }
  };

  // ❌ does care about child deps (year and routeData)
  // ❌ has to manually aggregate child deps
  const wrapWithHtml = ({ year, routeData }: { year: number; routeData: RouteData }) =>
    pipeWith(renderPage(true)({ year })(routeData), page => `<html>${page}</html>`);

  declare const routeData: RouteData;

  wrapWithHtml({ year: 2014, routeData });
 }

 {
  const renderCopyright = ({ routeData }: { routeData: RouteData }) =>
    RouteData.match(routeData, {
      Search: () => 'unsplash search copyright goes here',
      default: () => 'unsplash copyright goes here',
    });

  // ✅ doesn't care about child deps (routeData)
  const renderFooter = pipeWith(
    renderCopyright,
    chainW(copyright => ({ year }: { year: number }) => `<footer>${copyright} ${year}</footer>`),
  );

  // ✅ doesn't care about child deps (year and routeData)
  const renderPage = (hideFooter: boolean) => {
    if (hideFooter) {
      return Reader.of('<body>No Footer.</body>');
    } else {
      return pipeWith(
        renderFooter,
        Reader.map(footer => `<body>${footer}</body>`),
      );
    }
  };

  // ✅ doesn't care about child deps (year and routeData)
  const wrapWithHtml = pipeWith(
    renderPage(true),
    Reader.map(page => `<html>${page}</html>`),
  );

  declare const routeData: RouteData;

  wrapWithHtml({ year: 2014, routeData });
 }
	import * as Reader from 'fp-ts/lib/Reader';
	import { RouteData } from 'helpers/routes/types';
	import { pipe, pipeWith } from 'pipe-ts';

	// This will soon be part of fp-ts core
	// https://github.com/gcanti/fp-ts/issues/904#issuecomment-619346296
	const chainW: <Q, A, B>(
	f: (a: A) => Reader.Reader<Q, B>,
	) => <R>(ma: Reader.Reader<R, A>) => Reader.Reader<R & Q, B> = Reader.chain as Unrestricted;

	{
	const renderCopyright = RouteData.match({
	Search: () => 'unsplash search copyright goes here',
	default: () => 'unsplash copyright goes here',
	});

	// ✅ doesn't care about child deps (routeData)
	const renderFooter = (year: number) =>
	pipe(renderCopyright, copyright => `<footer>${copyright} ${year}</footer>`);

	// ❌ does care about child deps (year)
	const renderPage = (hideFooter: boolean) => ({ year }: { year: number }) => {
	if (hideFooter) {
	return () => '<body>No Footer.</body>';
	} else {
	return pipe(renderFooter(year), footer => `<body>${footer}</body>`);
	}
	};

	// ❌ does care about child deps (year and routeData)
	// ❌ has to manually aggregate child deps
	const wrapWithHtml = ({ year, routeData }: { year: number; routeData: RouteData }) =>
	pipeWith(renderPage(true)({ year })(routeData), page => `<html>${page}</html>`);

	declare const routeData: RouteData;

	wrapWithHtml({ year: 2014, routeData });
	}

	{
	const renderCopyright = ({ routeData }: { routeData: RouteData }) =>
	RouteData.match(routeData, {
	Search: () => 'unsplash search copyright goes here',
	default: () => 'unsplash copyright goes here',
	});

	// ✅ doesn't care about child deps (routeData)
	const renderFooter = pipeWith(
	renderCopyright,
	chainW(copyright => ({ year }: { year: number }) => `<footer>${copyright} ${year}</footer>`),
	);

	// ✅ doesn't care about child deps (year and routeData)
	const renderPage = (hideFooter: boolean) => {
	if (hideFooter) {
	return Reader.of('<body>No Footer.</body>');
	} else {
	return pipeWith(
	renderFooter,
	Reader.map(footer => `<body>${footer}</body>`),
	);
	}
	};

	// ✅ doesn't care about child deps (year and routeData)
	const wrapWithHtml = pipeWith(
	renderPage(true),
	Reader.map(page => `<html>${page}</html>`),
	);

	declare const routeData: RouteData;

	wrapWithHtml({ year: 2014, routeData });
	}