build: add tslint rule to enforce deletion targets

tools/tslint-rules/deletionTargetRule.ts

@@ -0,0 +1,61 @@
+import * as ts from 'typescript';
+import * as Lint from 'tslint';
+import * as utils from 'tsutils';
+import * as path from 'path';
+
+/**
+ * Rule ensuring that deletion targets have not expired.
+ * The current version is taken from the `package.json`.
+ */
+export class Rule extends Lint.Rules.AbstractRule {
+  apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+    const packageVersion = require(path.join(process.cwd(), 'package.json')).version;
+
+    return this.applyWithFunction(sourceFile, (ctx: Lint.WalkContext<any>) => {
+      utils.forEachComment(ctx.sourceFile, (file, {pos, end}) => {
+        const commentText = file.substring(pos, end);
+
+        if (commentText.indexOf('@deletion-target') === -1) {
+          return;
+        }
+
+        const version = commentText.match(/\d+\.\d+\.\d+/);
+
+        if (!version) {
+          ctx.addFailure(pos, end, '@deletion-target must have a version.');
+        } else if (this._hasExpired(packageVersion, version[0])) {
+          ctx.addFailure(pos, end, `Deletion target at ${version[0]} is due to be deleted. ` +
+                                   `Current version is ${packageVersion}.`);
+        }
+      });
+    });
+  }
+
+  /**
+   * Checks whether a version has expired, based on the current version.
+   * @param currentVersion Current version of the package.
+   * @param deletionTarget Version that is being checked.
+   */
+  private _hasExpired(currentVersion: string, deletionTarget: string) {
+    if (currentVersion === deletionTarget) {
+      return true;
+    }
+
+    const current = this._parseVersion(currentVersion);
+    const target = this._parseVersion(deletionTarget);
+
+    return target.major < current.major ||
+          (target.major === current.major && target.minor < current.minor) ||
+          (
+            target.major === current.major &&
+            target.minor === current.minor &&
+            target.patch < current.patch
+          );
+  }
+
+  /** Converts a version string into an object. */
+  private _parseVersion(version: string) {
+    const [major = 0, minor = 0, patch = 0] = version.split('.').map(segment => parseInt(segment));
+    return {major, minor, patch};
+  }
+}

tslint.json

@@ -120,6 +120,7 @@
       "./tools/package-tools/rollup-globals.ts",
       "src/+(lib|cdk|material-examples|material-experimental|cdk-experimental)/**/*.ts"
     ],
+    "deletion-target": true,
     "no-unescaped-html-tag": true
   }
 }