refactor(toolkit): move simple apis to shared helper package (#331)

Move the easier apis from cli package to the shared helper. Easier here
means little or no dependencies on other apis.

Tests will be moved later to keep the diff size managable. Code is still
tested as the tests are still running from `aws-cdk` package.

---
By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license

Author: mrgrain

.projenrc.ts

@@ -1162,6 +1162,11 @@ const toolkitLib = configureProject(
     name: '@aws-cdk/toolkit-lib',
     description: 'AWS CDK Programmatic Toolkit Library',
     srcdir: 'lib',
+    tsconfigDev: {
+      compilerOptions: {
+        rootDir: '.', // shouldn't be required but something broke... check again once we have gotten rid of the tmpToolkitHelpers package
+      },
+    },
     deps: [
       cloudAssemblySchema,
       // Purposely a ^ dependency so that clients selecting old toolkit library

packages/@aws-cdk/tmp-toolkit-helpers/src/api/context.ts

@@ -0,0 +1,108 @@
+import { Settings } from './settings';
+import { ToolkitError } from './toolkit-error';
+
+export { TRANSIENT_CONTEXT_KEY } from './settings';
+export const PROJECT_CONTEXT = 'cdk.context.json';
+
+interface ContextBag {
+  /**
+   * The file name of the context. Will be used to potentially
+   * save new context back to the original file.
+   */
+  fileName?: string;
+
+  /**
+   * The context values.
+   */
+  bag: Settings;
+}
+
+/**
+ * Class that supports overlaying property bags
+ *
+ * Reads come from the first property bag that can has the given key,
+ * writes go to the first property bag that is not readonly. A write
+ * will remove the value from all property bags after the first
+ * writable one.
+ */
+export class Context {
+  private readonly bags: Settings[];
+  private readonly fileNames: (string | undefined)[];
+
+  constructor(...bags: ContextBag[]) {
+    this.bags = bags.length > 0 ? bags.map((b) => b.bag) : [new Settings()];
+    this.fileNames =
+      bags.length > 0 ? bags.map((b) => b.fileName) : ['default'];
+  }
+
+  public get keys(): string[] {
+    return Object.keys(this.all);
+  }
+
+  public has(key: string) {
+    return this.keys.indexOf(key) > -1;
+  }
+
+  public get all(): { [key: string]: any } {
+    let ret = new Settings();
+
+    // In reverse order so keys to the left overwrite keys to the right of them
+    for (const bag of [...this.bags].reverse()) {
+      ret = ret.merge(bag);
+    }
+
+    return ret.all;
+  }
+
+  public get(key: string): any {
+    for (const bag of this.bags) {
+      const v = bag.get([key]);
+      if (v !== undefined) {
+        return v;
+      }
+    }
+    return undefined;
+  }
+
+  public set(key: string, value: any) {
+    for (const bag of this.bags) {
+      if (bag.readOnly) {
+        continue;
+      }
+
+      // All bags past the first one have the value erased
+      bag.set([key], value);
+      value = undefined;
+    }
+  }
+
+  public unset(key: string) {
+    this.set(key, undefined);
+  }
+
+  public clear() {
+    for (const key of this.keys) {
+      this.unset(key);
+    }
+  }
+
+  /**
+   * Save a specific context file
+   */
+  public async save(fileName: string): Promise<this> {
+    const index = this.fileNames.indexOf(fileName);
+
+    // File not found, don't do anything in this scenario
+    if (index === -1) {
+      return this;
+    }
+
+    const bag = this.bags[index];
+    if (bag.readOnly) {
+      throw new ToolkitError(`Context file ${fileName} is read only!`);
+    }
+
+    await bag.save(fileName);
+    return this;
+  }
+}

packages/@aws-cdk/tmp-toolkit-helpers/src/api/index.ts

@@ -1,10 +1,17 @@
 export * from './aws-auth';
 export * from './cloud-assembly';
 export * from './cloudformation';
+export * from './context';
 export * from './diff';
 export * from './io';
+export * from './notices';
 export * from './plugin';
 export * from './require-approval';
 export * from './resource-import';
-export * from './toolkit-error';
+export * from './rwlock';
 export * from './settings';
+export * from './stack-events';
+export * from './toolkit-error';
+export * from './work-graph';
+export * from './tree';
+export * from './tags';