fix: log why a device sync run failed #34

The sync adapter logged only the SyncResult counters of a run, so a
failed sync showed up in logcat as `ioErrors=1` and nothing else. The
reason was in the run's report, and JS warnings from a headless run
don't reach logcat; finding out that a run failed on "Invalid column
raw_contact_is_read_only" took reading the app's storage. The log line
now carries the report's outcome, its message (up to 300 characters)
and the number of failed items.

Checked: 55 JVM tests (`gradlew :app:testDebugUnitTest`, one new) and
the debug build.

android/app/src/main/java/com/anonymous/bulwarkmobile/sync/DeviceSyncAdapter.kt

@@ -91,7 +91,7 @@ class DeviceSyncAdapter(context: Context) :
             val outcome = SyncReports.outcome(run.report, run.endReason)
             SyncReports.apply(outcome, syncResult)
             Log.i(TAG, "Sync ${run.runId} of $authority ended (${run.endReason}) after " +
-                "${SystemClock.elapsedRealtime() - startedAt} ms: $outcome")
+                "${SystemClock.elapsedRealtime() - startedAt} ms: ${SyncReports.summary(run.report)}; $outcome")
         } catch (e: InterruptedException) {
             // onSyncCanceled interrupts this thread. JS sees the run as
             // cancelled at its next checkpoint (isRunCancelled).

android/app/src/main/java/com/anonymous/bulwarkmobile/sync/SyncReports.kt

@@ -74,6 +74,28 @@ object SyncReports {
         }
     }
 
+    /**
+     * One line for logcat: the report's outcome, its message and how many
+     * items failed. The reason a run failed is otherwise only in the report,
+     * and JS warnings from a headless run don't reach logcat.
+     */
+    fun summary(reportJson: String?): String {
+        if (reportJson == null) return "no report"
+        val report = try {
+            JSONObject(reportJson)
+        } catch (e: JSONException) {
+            return "unreadable report"
+        }
+        val parts = mutableListOf("outcome=" + report.optString("outcome", "?"))
+        val items = report.optJSONArray("itemErrors")?.length() ?: 0
+        if (items > 0) parts += "itemErrors=$items"
+        val message = report.optString("message", "")
+        if (message.isNotEmpty()) parts += "message=" + message.take(MAX_LOGGED_MESSAGE)
+        return parts.joinToString(" ")
+    }
+
+    private const val MAX_LOGGED_MESSAGE = 300
+
     fun apply(outcome: SyncOutcome, result: SyncResult) {
         result.stats.numIoExceptions += outcome.ioErrors
         result.stats.numAuthExceptions += outcome.authErrors

android/app/src/test/java/com/anonymous/bulwarkmobile/sync/SyncReportsTest.kt

@@ -81,4 +81,19 @@ class SyncReportsTest {
     fun `an outcome this build does not know is retried`() {
         assertEquals(1L, SyncReports.outcome(report("somethingNew"), "reported").ioErrors)
     }
+
+    @Test
+    fun `the log summary names the outcome, failed items and the message`() {
+        assertEquals("outcome=ok", SyncReports.summary(report("ok")))
+        assertEquals(
+            "outcome=internal message=Invalid column x",
+            SyncReports.summary(report("internal", ",\"message\":\"Invalid column x\"")),
+        )
+        val withItems = report("ok").replace("\"itemErrors\":[]", "\"itemErrors\":[{\"ref\":\"a\"},{\"ref\":\"b\"}]")
+        assertEquals("outcome=ok itemErrors=2", SyncReports.summary(withItems))
+        assertEquals("no report", SyncReports.summary(null))
+        assertEquals("unreadable report", SyncReports.summary("{"))
+        val long = SyncReports.summary(report("io", ",\"message\":\"" + "m".repeat(400) + "\""))
+        assertEquals("outcome=io message=".length + 300, long.length)
+    }
 }