Allow diffing of lcov files

Author: romeovs

README.md

@@ -23,6 +23,10 @@ action runner, use `${{ secrets.GITHUB_TOKEN }}`.
 The location of the lcov file to read the coverage report from. Defaults to
 `./coverage/lcov.info`.
 
+##### `lcov-base` (**Optional**)
+The location of the lcov file resulting from running the tests in the base
+branch. When this is set a diff of the coverage percentages is shown.
+
 ## Example usage
 
 ```yml

action.yml

@@ -11,6 +11,9 @@ inputs:
   lcov-file:
     description: The location of the lcov.info file
     required: false
+  lcov-base:
+    description: The location of the lcov file for the base branch
+    required: false
 runs:
   using: node12
   main: dist/main.js

dist/main.js

@@ -22881,7 +22881,7 @@ function uncovered(file, options) {
 		.join(", ")
 }
 
-function comment (lcov, options) {
+function comment$1 (lcov, options) {
 	return fragment(
 		`Coverage after merging ${b(options.head)} into ${b(options.base)}`,
 		table(tbody(tr(th(percentage(lcov).toFixed(2), "%")))),
@@ -22890,17 +22890,49 @@ function comment (lcov, options) {
 	)
 }
 
+function diff(lcov, before, options) {
+	if (!before) {
+		return comment$1(lcov, options)
+	}
+
+	const pbefore = percentage(before);
+	const pafter = percentage(lcov);
+	const pdiff = pafter - pbefore;
+	const plus = pdiff > 0 ? "+" : "";
+	const arrow =
+		pdiff === 0
+			? ""
+			: pdiff < 0
+				? "▾"
+				: "▴";
+
+	return fragment(
+		`Coverage after merging ${b(options.head)} into ${b(options.base)}`,
+		table(tbody(tr(
+			th(pafter.toFixed(2), "%"),
+			th(arrow, " ", plus, pdiff.toFixed(2), "%"),
+		))),
+		"\n\n",
+		details(summary("Coverage Report"), tabulate(lcov, options)),
+	)
+}
+
 async function main$1() {
 	const token = core$1.getInput("github-token");
 	const lcovFile = core$1.getInput("lcov-file") || "./coverage/lcov.info";
+	const baseFile = core$1.getInput("lcov-base");
 
 	const raw = await fs.promises.readFile(lcovFile, "utf-8").catch(err => null);
-
 	if (!raw) {
 		console.log(`No coverage report found at '${lcovFile}', exiting...`);
 		return
 	}
 
+	const baseRaw = baseFile && await fs.promises.readFile(baseFile, "utf-8").catch(err => null);
+	if (baseFile && !baseRaw) {
+		console.log(`No coverage report found at '${baseFile}', ignoring...`);
+	}
+
 	const options = {
 		repository: github_1.payload.repository.full_name,
 		commit: github_1.payload.pull_request.head.sha,
@@ -22910,7 +22942,8 @@ async function main$1() {
 	};
 
 	const lcov = await parse$2(raw);
-	const body = comment(lcov, options);
+	const baselcov = baseRaw && await parse$2(baseRaw);
+	const body = diff(lcov, baselcov, options);
 
 	await new github_2(token).issues.createComment({
 		repo: github_1.repo.repo,

src/cli.js

@@ -3,14 +3,22 @@ import { promises as fs } from "fs"
 import path from "path"
 
 import { parse } from "./lcov"
-import { comment } from "./comment"
+import { diff } from "./comment"
 
 async function main() {
 	const file = process.argv[2]
+	const beforeFile = process.argv[3]
 	const prefix = path.dirname(path.dirname(path.resolve(file))) + "/"
 
 	const content = await fs.readFile(file, "utf-8")
 	const lcov = await parse(content)
+
+	let before
+	if (beforeFile) {
+		const content = await fs.readFile(beforeFile, "utf-8")
+		before = await parse(content)
+	}
+
 	const options = {
 		repository: "example/foo",
 		commit: "f9d42291812ed03bb197e48050ac38ac6befe4e5",
@@ -19,7 +27,7 @@ async function main() {
 		base: "master",
 	}
 
-	console.log(comment(lcov, options))
+	console.log(diff(lcov, before, options))
 }
 
 main().catch(function(err) {

src/comment.js

@@ -11,3 +11,30 @@ export function comment (lcov, options) {
 		details(summary("Coverage Report"), tabulate(lcov, options)),
 	)
 }
+
+export function diff(lcov, before, options) {
+	if (!before) {
+		return comment(lcov, options)
+	}
+
+	const pbefore = percentage(before)
+	const pafter = percentage(lcov)
+	const pdiff = pafter - pbefore
+	const plus = pdiff > 0 ? "+" : ""
+	const arrow =
+		pdiff === 0
+			? ""
+			: pdiff < 0
+				? "▾"
+				: "▴"
+
+	return fragment(
+		`Coverage after merging ${b(options.head)} into ${b(options.base)}`,
+		table(tbody(tr(
+			th(pafter.toFixed(2), "%"),
+			th(arrow, " ", plus, pdiff.toFixed(2), "%"),
+		))),
+		"\n\n",
+		details(summary("Coverage Report"), tabulate(lcov, options)),
+	)
+}

src/index.js

@@ -3,19 +3,24 @@ import core from "@actions/core"
 import { GitHub, context } from "@actions/github"
 
 import { parse } from "./lcov"
-import { comment } from "./comment"
+import { diff } from "./comment"
 
 async function main() {
 	const token = core.getInput("github-token")
 	const lcovFile = core.getInput("lcov-file") || "./coverage/lcov.info"
+	const baseFile = core.getInput("lcov-base")
 
 	const raw = await fs.readFile(lcovFile, "utf-8").catch(err => null)
-
 	if (!raw) {
 		console.log(`No coverage report found at '${lcovFile}', exiting...`)
 		return
 	}
 
+	const baseRaw = baseFile && await fs.readFile(baseFile, "utf-8").catch(err => null)
+	if (baseFile && !baseRaw) {
+		console.log(`No coverage report found at '${baseFile}', ignoring...`)
+	}
+
 	const options = {
 		repository: context.payload.repository.full_name,
 		commit: context.payload.pull_request.head.sha,
@@ -25,7 +30,8 @@ async function main() {
 	}
 
 	const lcov = await parse(raw)
-	const body = comment(lcov, options)
+	const baselcov = baseRaw && await parse(baseRaw)
+	const body = diff(lcov, baselcov, options)
 
 	await new GitHub(token).issues.createComment({
 		repo: context.repo.repo,