build: convert dedent.ts and tests to TypeScript (#51)

Fixes #50.

Integrates with a few tools:

* TypeScript itself for type checking (`yarn tsc`)
* [Babel's TypeScript
preset](https://babeljs.io/docs/babel-preset-typescript) to stick with
the existing output process (`yarn build:legacy`, `yarn build:modern`)
* [tsup](https://tsup.egoist.dev) to generate a single `.d.ts` from
`dedent.ts` (`yarn build:types`)

Types are moved from `index.d.ts` to `dist/dedent.d.ts` to match the
other `dist/*` files. I confirmed with [the `attw`
cli](https://github.com/arethetypeswrong/arethetypeswrong.github.io/tree/e33adb4d894b041a51b8366bf0611ff5ecaf38cb/packages/cli)
that these support various Node resolution strategies.

`macro.js` and `macro.d.ts` are untouched, per #50 -> #52.

.babelrc

@@ -3,6 +3,7 @@
     "legacy": {
       "plugins": [["add-module-exports", { "addDefaultProperty": true }]],
       "presets": [
+        "@babel/preset-typescript",
         [
           "@babel/preset-env",
           {
@@ -16,6 +17,7 @@
     },
     "modern": {
       "presets": [
+        "@babel/preset-typescript",
         [
           "@babel/preset-env",
           {
@@ -30,6 +32,7 @@
     }
   },
   "presets": [
+    "@babel/preset-typescript",
     [
       "@babel/preset-env",
       {
@@ -39,6 +42,5 @@
         }
       }
     ]
-  ],
-  "plugins": ["@babel/plugin-transform-flow-comments"]
+  ]
 }

.eslintignore

@@ -0,0 +1,4 @@
+dist/
+
+# https://github.com/dmnd/dedent/issues/52
+macro.js

.eslintrc.js

@@ -0,0 +1,13 @@
+/* eslint-env node */
+module.exports = {
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    project: true,
+    tsconfigRootDir: __dirname,
+  },
+  extends: [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/strict-type-checked",
+    "plugin:@typescript-eslint/stylistic-type-checked",
+  ],
+};

__tests__/dedent-tests.js → __tests__/dedent-tests.ts

@@ -1,6 +1,4 @@
-// @flow
-
-import dd from '../dedent';
+import dd from "../dedent";
 
 describe("dedent", () => {
   it("works without interpolation", () => {
@@ -69,15 +67,16 @@ describe("dedent", () => {
 
     it("works with single line and inline closing backtick", () => {
       expect(dd`
-        A single line of input.`
-      ).toMatchSnapshot();
+        A single line of input.`).toMatchSnapshot();
     });
   });
 
   it("can be used as a function", () => {
-    expect(dd(`
+    expect(
+      dd(`
       A test argument.
-    `)).toMatchSnapshot();
+    `)
+    ).toMatchSnapshot();
   });
 
   it("escapes backticks", () => {
@@ -110,9 +109,7 @@ describe("dedent", () => {
   });
 
   it("works with escaped tabs for indentation", () => {
-    expect(
-      dd("\t\tfirst\n\t\t\tsecond\n\t\t\t\tthird")
-    ).toMatchSnapshot();
+    expect(dd("\t\tfirst\n\t\t\tsecond\n\t\t\t\tthird")).toMatchSnapshot();
   });
   /* eslint-enable indent */
 });

dedent.ts

@@ -0,0 +1,59 @@
+export default function dedent(literals: string): string;
+export default function dedent(
+  strings: TemplateStringsArray,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  ...values: any[]
+): string;
+export default function dedent(
+  strings: string | TemplateStringsArray,
+  ...values: string[]
+) {
+  const raw = typeof strings === "string" ? [strings] : strings.raw;
+
+  // first, perform interpolation
+  let result = "";
+  for (let i = 0; i < raw.length; i++) {
+    result += raw[i]
+      // join lines when there is a suppressed newline
+      .replace(/\\\n[ \t]*/g, "")
+      // handle escaped backticks
+      .replace(/\\`/g, "`");
+
+    if (i < values.length) {
+      result += values[i];
+    }
+  }
+
+  // now strip indentation
+  const lines = result.split("\n");
+  let mindent: number | null = null;
+  for (const l of lines) {
+    const m = l.match(/^(\s+)\S+/);
+    if (m) {
+      const indent = m[1].length;
+      if (!mindent) {
+        // this is the first indented line
+        mindent = indent;
+      } else {
+        mindent = Math.min(mindent, indent);
+      }
+    }
+  }
+
+  if (mindent !== null) {
+    const m = mindent; // appease TypeScript
+    result = lines
+      // https://github.com/typescript-eslint/typescript-eslint/issues/7140
+      // eslint-disable-next-line @typescript-eslint/prefer-string-starts-ends-with
+      .map((l) => (l[0] === " " || l[0] === "\t" ? l.slice(m) : l))
+      .join("\n");
+  }
+
+  return (
+    result
+      // dedent eats leading and trailing whitespace too
+      .trim()
+      // handle escaped newlines at the end to ensure they don't get stripped too
+      .replace(/\\n/g, "\n")
+  );
+}