cmd/mbf: jstest: add JSON reporter for go test integration

cmd/mbf/internal/pkgserver/ui/jstest/jstest.ts

@@ -23,6 +23,7 @@ export class TestRegistrar {
     }
 
     run(reporter: Reporter) {
+        reporter.register(this.#suites);
         for (const suite of this.#suites) {
             for (const c of suite.children) runTests(reporter, [suite.name], c);
         }
@@ -141,6 +142,9 @@ function extractExceptionString(e: any): string {
 // Reporting
 
 export interface Reporter {
+    // A notable feature—or flaw, to some—of the DSL is that the tree of tests
+    // is statically known, which might greatly aid in implementing a reporter.
+    register(suites: TestGroup[]): void;
     // While we could simply call a function with a tree representing all
     // results, which would indeed greatly simplify implementation of reporters,
     // simply registering a path and allowing the reporter to—either implicitly
@@ -170,14 +174,20 @@ export interface Reporter {
 // underlying result tree; this makes it extremely convenient in some cases like
 // testing ourself.
 export class NoOpReporter implements Reporter {
+    suites: TestGroup[];
     results: ({ path: string[] } & TestResult)[];
     finalized: boolean;
 
     constructor() {
+        this.suites = [];
         this.results = [];
         this.finalized = false;
     }
 
+    register(suites: TestGroup[]) {
+        this.suites = suites;
+    }
+
     update(path: string[], result: TestResult) {
         this.results.push({ path, ...result });
     }
@@ -211,6 +221,9 @@ export class StreamReporter implements Reporter {
         return this.counts.successes > 0 && this.counts.failures === 0;
     }
 
+    // We don't need the structure for reporting.
+    register(suites: TestGroup[]) {}
+
     update(path: string[], result: TestResult) {
         if (path.length === 0) throw new RangeError("path is empty");
         const pathStr = path.join(SEP);
@@ -300,6 +313,13 @@ function assertGetElementById(id: string): HTMLElement {
 // A reporter that directly translates a tree of results into a tree of
 // collapsible elements in the DOM.
 export class DOMReporter implements Reporter {
+    // It is very difficult to implement this using the statically known tree,
+    // because Map doesn't handle array keys properly (to store the path), and
+    // it's unknown of there's any way to implement it without writing one's own
+    // data types. Oh well; using the DOM as a data structure might seem hacky
+    // but it does have its benefits, apart from encouraging a tagless final.
+    register(suites: TestGroup[]) {}
+
     update(path: string[], result: TestResult) {
         if (path.length === 0) throw new RangeError("path is empty");
         const counter = assertGetElementById(result.success ? "successes" : "failures");
@@ -349,3 +369,34 @@ export class DOMReporter implements Reporter {
 
     finalize() {}
 }
+
+interface GoNode {
+    name: string;
+    subtests?: GoNode[];
+}
+
+// Used to display results via `go test`, via some glue code from the Go side.
+// TODO(Ophestra): said glue code has to be written.
+export class GoTestReporter implements Reporter {
+    register(suites: TestGroup[]) {
+        console.log(JSON.stringify(suites.map(GoTestReporter.serialize)));
+    }
+
+    // Convert a test tree into the one expected by the Go code.
+    static serialize(node: TestTree): GoNode {
+        return {
+            name: node.name,
+            subtests: "children" in node ? node.children.map(GoTestReporter.serialize) : undefined,
+        };
+    }
+
+    update(path: string[], result: TestResult) {
+        console.log(JSON.stringify({ path, ...result }));
+    }
+
+    // Unnecessary but convenient on the Go side, so that it doesn't have to
+    // infer this via process exit.
+    finalize() {
+        console.log("null");
+    }
+}