Document and clean up the provider construction module

packages/buidler-core/src/internal/core/providers/construction.ts

@@ -17,6 +17,16 @@ export function isHDAccountsConfig(
  return accounts !== undefined && Object.keys(accounts).includes("mnemonic");
 }
 
+function isHttpNetworkConfig(
+ netConfig: NetworkConfig
+): netConfig is HttpNetworkConfig {
+ return "url" in netConfig;
+}
+
+// This function is let's you import a provider dynamically in a pretty
+// type-safe way.
+// `ProviderNameT` and `name` must be the same literal string. TS enforces it.
+// `ModuleT` and `filePath` must also be the same, but this is not enforced.
 function importProvider<ModuleT, ProviderNameT extends keyof ModuleT>(
  filePath: string,
  name: ProviderNameT
@@ -133,11 +143,8 @@ export function applyProviderWrappers(
  "ChainIdValidatorProvider"
  >("./chainId", "ChainIdValidatorProvider");
 
- const isHttpNetworkConfig = "url" in netConfig;
-
- if (isHttpNetworkConfig) {
- const httpNetConfig = netConfig as Partial<HttpNetworkConfig>;
- const accounts = httpNetConfig.accounts;
+ if (isHttpNetworkConfig(netConfig)) {
+ const accounts = netConfig.accounts;
 
  if (Array.isArray(accounts)) {
  provider = new LocalAccountsProvider(provider, accounts);
@@ -153,7 +160,7 @@ export function applyProviderWrappers(
 
  // TODO: Add some extension mechanism for account plugins here
 
- if (typeof httpNetConfig.gas !== "number") {
+ if (typeof netConfig.gas !== "number") {
  provider = new GanacheGasMultiplierProvider(provider);
  }
  }
@@ -176,7 +183,7 @@ export function applyProviderWrappers(
  provider = new FixedGasPriceProvider(provider, netConfig.gasPrice);
  }
 
- if (isHttpNetworkConfig && netConfig.chainId !== undefined) {
+ if (isHttpNetworkConfig(netConfig) && netConfig.chainId !== undefined) {
  provider = new ChainIdValidatorProvider(provider, netConfig.chainId);
  }