Use init script to capture build scan URL

Instead of parsing the log output, we instead register a
buildScanPublished listener and record the build scan URL
to a file. This file is subsequently read to report the
build scan URL.

Fixes #30

src/execution.ts

@@ -1,29 +1,36 @@
 import * as exec from '@actions/exec'
+import fs from 'fs'
+import path from 'path'
+import {writeInitScript} from './gradle-init'
 
 export async function execute(
     executable: string,
     root: string,
-    argv: string[]
+    args: string[]
 ): Promise<BuildResult> {
-    let publishing = false
     let buildScanUrl: string | undefined
 
-    const status: number = await exec.exec(executable, argv, {
+    // TODO: instead of running with no-daemon, run `--stop` in post action.
+    args.push('--no-daemon')
+
+    const initScript = writeInitScript()
+    args.push('--init-script')
+    args.push(initScript)
+
+    const buildScanFile = path.resolve(root, 'gradle-build-scan.txt')
+    if (fs.existsSync(buildScanFile)) {
+        fs.unlinkSync(buildScanFile)
+    }
+
+    const status: number = await exec.exec(executable, args, {
         cwd: root,
-        ignoreReturnCode: true,
-        listeners: {
-            stdline: (line: string) => {
-                if (line.includes('Publishing build scan...')) {
-                    publishing = true
-                }
-                if (publishing && line.startsWith('http')) {
-                    buildScanUrl = line.trim()
-                    publishing = false
-                }
-            }
-        }
+        ignoreReturnCode: true
     })
 
+    if (fs.existsSync(buildScanFile)) {
+        buildScanUrl = fs.readFileSync(buildScanFile, 'utf-8')
+    }
+
     return new BuildResultImpl(status, buildScanUrl)
 }
 

src/gradle-init.ts

@@ -0,0 +1,52 @@
+import fs from 'fs'
+import path from 'path'
+import * as core from '@actions/core'
+
+export function writeInitScript(): string {
+    const tmpDir = process.env['RUNNER_TEMP'] || ''
+    const initScript = path.resolve(tmpDir, 'build-scan-capture.init.gradle')
+    core.info(`Writing init script: ${initScript}`)
+    if (fs.existsSync(initScript)) {
+        return initScript
+    }
+    fs.writeFileSync(
+        initScript,
+        `
+import org.gradle.util.GradleVersion
+
+// Don't run against the included builds (if the main build has any).
+def isTopLevelBuild = gradle.getParent() == null
+if (isTopLevelBuild) {
+    def version = GradleVersion.current().baseVersion
+    def atLeastGradle5 = version >= GradleVersion.version("5.0")
+    def atLeastGradle6 = version >= GradleVersion.version("6.0")
+
+    if (atLeastGradle6) {
+        settingsEvaluated { settings ->
+            if (settings.pluginManager.hasPlugin("com.gradle.enterprise")) {
+                registerCallbacks(settings.extensions["gradleEnterprise"], settings.rootProject.name)
+            }
+        }
+    } else if (atLeastGradle5) {
+        projectsEvaluated { gradle ->
+            if (gradle.rootProject.pluginManager.hasPlugin("com.gradle.build-scan")) {
+                registerCallbacks(gradle.rootProject.extensions["gradleEnterprise"], gradle.rootProject.name)
+            }
+        }
+    }
+}
+
+def registerCallbacks(gradleEnterprise, rootProjectName) {
+    gradleEnterprise.with {
+        buildScan {
+            def scanFile = new File("gradle-build-scan.txt")
+            buildScanPublished { buildScan ->
+                scanFile.text = buildScan.buildScanUri
+            }
+        }
+    }
+}
+`
+    )
+    return initScript
+}

src/main.ts

@@ -16,8 +16,6 @@ export async function run(): Promise<void> {
         await caches.restore(buildRootDirectory)
 
         const args: string[] = parseCommandLineArguments()
-        // TODO: instead of running with no-daemon, run `--stop` in post action.
-        args.push('--no-daemon')
 
         const result = await execution.execute(
             await resolveGradleExecutable(