refactor(ivy): ngcc - implement new module resolver (#29643)

When working out the dependencies between entry-points
ngcc must parse the import statements and then resolve the
import path to the actual file.  This is complicated because module
resolution is not trivial.

Previously ngcc used the node.js `require.resolve`, with some
hacking to resolve modules. This change refactors the `DependencyHost`
to use a new custom `ModuleResolver`, which is optimized for this use
case.

Moreover, because we are in full control of the resolution,
we can support TS `paths` aliases, where not all imports come from
`node_modules`. This is the case in some CLI projects where there are
compiled libraries that are stored locally in a `dist` folder.
See //FW-1210.

PR Close #29643

packages/compiler-cli/ngcc/src/utils.ts

@@ -51,3 +51,17 @@ export function hasNameIdentifier(declaration: ts.Declaration): declaration is t
   const namedDeclaration: ts.Declaration&{name?: ts.Node} = declaration;
   return namedDeclaration.name !== undefined && ts.isIdentifier(namedDeclaration.name);
 }
+
+export type PathMappings = {
+  baseUrl: string,
+  paths: {[key: string]: string[]}
+};
+
+/**
+ * Test whether a path is "relative".
+ *
+ * Relative paths start with `/`, `./` or `../`; or are simply `.` or `..`.
+ */
+export function isRelativePath(path: string): boolean {
+  return /^\/|^\.\.?($|\/)/.test(path);
+}