From 4889a0486dd68d2d3d808497a2d0a9f1c36dea13 Mon Sep 17 00:00:00 2001
From: Anders Kaseorg <anders@zulipchat.com>
Date: Mon, 10 Feb 2020 03:32:56 -0800
Subject: [PATCH] tests: Compile Handlebars templates with source maps.

This allows us to collect coverage for Handlebars templates, and also
improves the readability of Handlebars-related stack traces.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
---
 frontend_tests/zjsunit/handlebars.js | 88 +++++++++++++++-------------
 tools/test-js-with-node              |  2 +-
 2 files changed, 48 insertions(+), 42 deletions(-)

diff --git a/frontend_tests/zjsunit/handlebars.js b/frontend_tests/zjsunit/handlebars.js
index 75ea98ef6b..209babfaf7 100644
--- a/frontend_tests/zjsunit/handlebars.js
+++ b/frontend_tests/zjsunit/handlebars.js
@@ -1,52 +1,58 @@
 const fs = require("fs");
+const Handlebars = require("handlebars/dist/cjs/handlebars.js");
 const path = require("path");
+const { SourceMapConsumer, SourceNode } = require("source-map");
 
 const templates_path = path.resolve(__dirname, "../../static/templates");
-let render;
 
-exports.make_handlebars = () => {
-    // Create a new Handlebars instance.
-    const Handlebars = require("handlebars/dist/cjs/handlebars.js");
-    const hb = Handlebars.create();
-
-    const compiled = new Set();
-    const compileFile = filename => {
-        const name = "$" + path.relative(templates_path, filename);
-        if (!compiled.has(name)) {
-            compiled.add(name);
-            hb.registerPartial(
-                name,
-                hb.compile(fs.readFileSync(filename, "utf-8"), { preventIndent: true, zjsFilename: filename })
-            );
-        }
-        return name;
-    };
-
-    class ZJavaScriptCompiler extends hb.JavaScriptCompiler {
-        nameLookup(parent, name, type) {
-            // Auto-register partials with relative paths, like handlebars-loader.
-            if (type === "partial" && name !== "@partial-block") {
-                name = compileFile(path.resolve(path.dirname(this.options.zjsFilename), name + ".hbs"));
-            }
-            return super.nameLookup(parent, name, type);
-        }
-    }
-
-    ZJavaScriptCompiler.prototype.compiler = ZJavaScriptCompiler;
-    hb.JavaScriptCompiler = ZJavaScriptCompiler;
-
-    render = (filename, ...args) => hb.partials[compileFile(filename)](...args);
-
-    return hb;
-};
+exports.make_handlebars = () => Handlebars.create();
 
 exports.stub_templates = stub => {
-    render = (filename, ...args) => {
-        const name = path.relative(templates_path, filename).slice(0, -".hbs".length);
-        return stub(name, ...args);
-    };
+    window.template_stub = stub;
 };
 
+const hb = Handlebars.create();
+
+class ZJavaScriptCompiler extends hb.JavaScriptCompiler {
+    nameLookup(parent, name, type) {
+        // Auto-register partials with relative paths, like handlebars-loader.
+        if (type === "partial" && name !== "@partial-block") {
+            const filename = path.resolve(path.dirname(this.options.srcName), name + ".hbs");
+            return ["require(", JSON.stringify(filename), ")"];
+        }
+        return super.nameLookup(parent, name, type);
+    }
+}
+
+ZJavaScriptCompiler.prototype.compiler = ZJavaScriptCompiler;
+hb.JavaScriptCompiler = ZJavaScriptCompiler;
+
 require.extensions[".hbs"] = (module, filename) => {
-    module.exports = (...args) => render(filename, ...args);
+    const code = fs.readFileSync(filename, "utf-8");
+    const name = path.relative(templates_path, filename).slice(0, -".hbs".length);
+    const pc = hb.precompile(code, { preventIndent: true, srcName: filename });
+    const node = new SourceNode();
+    node.add([
+        "let hb, template;\n",
+        "module.exports = (...args) => {\n",
+        "    if (window.template_stub !== undefined) {\n",
+        "        return window.template_stub(",
+        JSON.stringify(name),
+        ", ...args);\n",
+        "    }\n",
+        "    if (hb !== Handlebars) {\n",
+        "        template = (hb = Handlebars).template(",
+        SourceNode.fromStringWithSourceMap(pc.code, new SourceMapConsumer(pc.map)),
+        ");\n",
+        "    }\n",
+        "    return template(...args);\n",
+        "};\n",
+    ]);
+    const out = node.toStringWithSourceMap();
+    module._compile(
+        out.code +
+            "\n//# sourceMappingURL=data:application/json;charset=utf-8;base64," +
+            Buffer.from(out.map.toString()).toString("base64"),
+        filename
+    );
 };
diff --git a/tools/test-js-with-node b/tools/test-js-with-node
index 5d87002e4c..cc19743f54 100755
--- a/tools/test-js-with-node
+++ b/tools/test-js-with-node
@@ -202,7 +202,7 @@ def run_tests_via_node_js() -> int:
         coverage_lcov_file = os.path.join(coverage_dir, 'lcov.info')
 
         nyc = os.path.join(ROOT_DIR, 'node_modules/.bin/nyc')
-        command = [nyc, '--extension', '.ts']
+        command = [nyc, '--extension', '.hbs', '--extension', '.ts']
         command += ['--report-dir', coverage_dir]
         command += ['--temp-directory', coverage_dir, '-r=text-summary']
         command += node_tests_cmd