chore: output declaration files for neuroglancer packages (#576)

* chore: output declaration files for neuroglancer when installed with NPM

Add --declaration flag to build-package.ts to optionally output typescript declaration files
Enable flag for npm prepare script

* fix: improve declarations by using tsconfig.json

* always generate declaration files when building packages

* remove unnecessary use of ts.createCompilerHost

build_tools/build-package.ts

@@ -14,10 +14,24 @@ import fs from "node:fs/promises";
 import path from "node:path";
 import esbuild from "esbuild";
 import { glob } from "glob";
+import ts from "typescript";
 import yargs from "yargs";
 
 const rootDir = path.resolve(import.meta.dirname, "..");
 
+function buildDeclarationFiles(
+ fileNames: string[],
+ options: ts.CompilerOptions,
+): void {
+ options = {
+ ...options,
+ declaration: true,
+ emitDeclarationOnly: true,
+ };
+ const program = ts.createProgram(fileNames, options);
+ program.emit();
+}
+
 async function buildPackage(options: { inplace?: boolean }) {
  const { inplace = false } = options;
 
@@ -45,13 +59,32 @@ async function buildPackage(options: { inplace?: boolean }) {
  nodir: true,
  });
 
+ const entryPoints = typescriptSources.map((name) =>
+ path.resolve(srcDir, name),
+ );
+
  await esbuild.build({
- entryPoints: typescriptSources.map((name) => path.resolve(srcDir, name)),
+ entryPoints,
  outbase: srcDir,
  bundle: false,
  outdir: libDir,
  });
 
+ let compilerOptionsFromConfigFile: ts.CompilerOptions = {};
+ const configFileName = ts.findConfigFile("../", ts.sys.fileExists);
+ if (configFileName) {
+ const configFile = ts.readConfigFile(configFileName, ts.sys.readFile);
+ compilerOptionsFromConfigFile = ts.parseJsonConfigFileContent(
+ configFile.config,
+ ts.sys,
+ "./",
+ ).options;
+ }
+ buildDeclarationFiles(entryPoints, {
+ ...compilerOptionsFromConfigFile,
+ outDir: libDir,
+ });
+
  const otherSources = await glob(["**/*.{css,js,html,wasm}"], {
  cwd: srcDir,
  nodir: true,