feat(common): add Checks#nonBlankString() utility

Asserts that a string is not a blank one. Handy when
you do not just need to know that something is truthy
but also that it is not an empty string or one that
only contains whitespaces (which is still a blank one)

Signed-off-by: Peter Somogyvari <peter.somogyvari@accenture.com>

packages/cactus-common/src/main/typescript/checks.ts

@@ -18,4 +18,23 @@ export class Checks {
       throw new CodedError(message, code);
     }
   }
+
+  /**
+   * Verifies that a string is indeed not a blank string.
+   * Blank string can be one that only has whitespace characters for example.
+   *
+   * @param value The value that will be asserted for being a non-blank string.
+   * @param subject The error message if `value` is a blank string.
+   * @param code The code of the error if `checkResult is falsy.
+   */
+  public static nonBlankString(
+    value: any,
+    subject: string = "variable",
+    code: string = "-1"
+  ): void {
+    if (typeof value !== "string" || value.trim().length === 0) {
+      const message = `"${subject}" is a blank string. Need non-blank.`;
+      throw new CodedError(message, code);
+    }
+  }
 }

packages/cactus-common/src/test/typescript/unit/checks.test.ts

@@ -0,0 +1,27 @@
+import test, { Test } from "tape";
+
+import { v4 as uuidv4 } from "uuid";
+
+import { Checks } from "../../../main/typescript";
+
+test("Checks", (t: Test) => {
+  test("Checks#nonBlankString()", (t2: Test) => {
+    const subject = uuidv4();
+    const pattern = new RegExp(`${subject}`);
+
+    t2.throws(() => Checks.nonBlankString("", subject), pattern);
+    t2.throws(() => Checks.nonBlankString(" ", subject), pattern);
+    t2.throws(() => Checks.nonBlankString("\n", subject), pattern);
+    t2.throws(() => Checks.nonBlankString("\t", subject), pattern);
+    t2.throws(() => Checks.nonBlankString("\t\n", subject), pattern);
+    t2.throws(() => Checks.nonBlankString("\n\r", subject), pattern);
+
+    t2.doesNotThrow(() => Checks.nonBlankString("-"));
+    t2.doesNotThrow(() => Checks.nonBlankString(" a "));
+    t2.doesNotThrow(() => Checks.nonBlankString("\na\t"));
+
+    t2.end();
+  });
+
+  t.end();
+});