Support importing partial JSON files (#202)

Partial files are allowed in many specs, e.g. Trace Event Format,
so the viewer should be able to load partial files as well.

package.json

@@ -44,7 +44,8 @@
     "ts-jest": "22.4.6",
     "typescript": "2.8.1",
     "typescript-eslint-parser": "17.0.1",
-    "uglify-es": "3.2.2"
+    "uglify-es": "3.2.2",
+    "partial-json-parser": "1.0.3"
   },
   "jest": {
     "transform": {

sample/profiles/trace-event/simple-object-partial.json

@@ -0,0 +1,7 @@
+{
+  "traceEvents": [
+    {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
+    {"pid": 0, "tid": 0, "ph": "B", "name": "beta", "ts": 1},
+    {"pid": 0, "tid": 0, "ph": "X", "ts": 7, "tdur": 4},
+    {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 13},
+    {"pid": 0, "tid": 0, "ph": "E", "name": "alpha", "ts": 14},

sample/profiles/trace-event/simple-partial.json

@@ -0,0 +1,7 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "beta", "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "X", "name": "gamma", "ts": 2, "dur": 5, "args": {"detail": "foobar"}},
+  {"pid": 0, "tid": 0, "ph": "X", "name": "epsilon", "ts": 7, "tdur": 4},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 13},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "alpha", "ts": 14},

src/import/__snapshots__/trace-event.test.ts.snap

@@ -258,10 +258,112 @@ Object {
 }
 `;
 
+exports[`importTraceEvents simple object partial 1`] = `
+Object {
+  "frames": Array [
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "alpha",
+      "line": undefined,
+      "name": "alpha",
+      "selfWeight": 2,
+      "totalWeight": 14,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "beta",
+      "line": undefined,
+      "name": "beta",
+      "selfWeight": 8,
+      "totalWeight": 12,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "(unnamed)",
+      "line": undefined,
+      "name": "(unnamed)",
+      "selfWeight": 4,
+      "totalWeight": 4,
+    },
+  ],
+  "name": "pid 0, tid 0",
+  "stacks": Array [
+    "alpha 1.00µs",
+    "alpha;beta 6.00µs",
+    "alpha;beta;(unnamed) 4.00µs",
+    "alpha;beta 2.00µs",
+    "alpha 1.00µs",
+  ],
+}
+`;
+
+exports[`importTraceEvents simple object partial: indexToView 1`] = `0`;
+
+exports[`importTraceEvents simple object partial: profileGroup.name 1`] = `"simple-object-partial.json"`;
+
 exports[`importTraceEvents simple object: indexToView 1`] = `0`;
 
 exports[`importTraceEvents simple object: profileGroup.name 1`] = `"simple-object.json"`;
 
+exports[`importTraceEvents simple partial 1`] = `
+Object {
+  "frames": Array [
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "alpha",
+      "line": undefined,
+      "name": "alpha",
+      "selfWeight": 2,
+      "totalWeight": 14,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "beta",
+      "line": undefined,
+      "name": "beta",
+      "selfWeight": 3,
+      "totalWeight": 12,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "gamma {\\"detail\\":\\"foobar\\"}",
+      "line": undefined,
+      "name": "gamma {\\"detail\\":\\"foobar\\"}",
+      "selfWeight": 5,
+      "totalWeight": 5,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "epsilon",
+      "line": undefined,
+      "name": "epsilon",
+      "selfWeight": 4,
+      "totalWeight": 4,
+    },
+  ],
+  "name": "pid 0, tid 0",
+  "stacks": Array [
+    "alpha 1.00µs",
+    "alpha;beta 1.00µs",
+    "alpha;beta;gamma {\\"detail\\":\\"foobar\\"} 5.00µs",
+    "alpha;beta;epsilon 4.00µs",
+    "alpha;beta 2.00µs",
+    "alpha 1.00µs",
+  ],
+}
+`;
+
+exports[`importTraceEvents simple partial: indexToView 1`] = `0`;
+
+exports[`importTraceEvents simple partial: profileGroup.name 1`] = `"simple-partial.json"`;
+
 exports[`importTraceEvents simple: indexToView 1`] = `0`;
 
 exports[`importTraceEvents simple: profileGroup.name 1`] = `"simple.json"`;

src/import/index.ts

@@ -1,6 +1,8 @@
 import {Profile, ProfileGroup} from '../lib/profile'
 import {FileSystemDirectoryEntry} from './file-system-entry'
 
+import {partialParse} from 'partial-json-parser'
+
 import {
   importFromChromeCPUProfile,
   importFromChromeTimeline,
@@ -71,6 +73,14 @@ function toGroup(profile: Profile | null): ProfileGroup | null {
   return {name: profile.getName(), indexToView: 0, profiles: [profile]}
 }
 
+function tryImportTraceEvents(parsed: any): ProfileGroup | null {
+  if (isTraceEventFormatted(parsed)) {
+    console.log('Importing as Trace Event Format profile')
+    return importTraceEvents(parsed)
+  }
+  return null
+}
+
 async function _importProfileGroup(dataSource: ProfileDataSource): Promise<ProfileGroup | null> {
   const fileName = await dataSource.name()
 
@@ -115,6 +125,7 @@ async function _importProfileGroup(dataSource: ProfileDataSource): Promise<Profi
 
   // Second pass: Try to guess what file format it is based on structure
   let parsed: any
+  let profileGroup: ProfileGroup | null
   try {
     parsed = JSON.parse(contents)
   } catch (e) {}
@@ -131,9 +142,8 @@ async function _importProfileGroup(dataSource: ProfileDataSource): Promise<Profi
     } else if ('nodes' in parsed && 'samples' in parsed && 'timeDeltas' in parsed) {
       console.log('Importing as Chrome CPU Profile')
       return toGroup(importFromChromeCPUProfile(parsed))
-    } else if (isTraceEventFormatted(parsed)) {
-      console.log('Importing as Trace Event Format profile')
-      return importTraceEvents(parsed)
+    } else if ((profileGroup = tryImportTraceEvents(parsed))) {
+      return profileGroup
     } else if ('head' in parsed && 'samples' in parsed && 'timestamps' in parsed) {
       console.log('Importing as Chrome CPU Profile (old format)')
       return toGroup(importFromOldV8CPUProfile(parsed))
@@ -175,6 +185,17 @@ async function _importProfileGroup(dataSource: ProfileDataSource): Promise<Profi
     }
   }
 
+  // Third pass: try parsing partial JSON file, as some of the formats,
+  // e.g. Trace Event Format, allow partial files.
+  try {
+    parsed = partialParse(contents)
+  } catch {}
+  if (parsed) {
+    if ((profileGroup = tryImportTraceEvents(parsed))) {
+      return profileGroup
+    }
+  }
+
   // Unrecognized format
   return null
 }

src/import/partial-json-parser.d.ts

@@ -0,0 +1 @@
+declare module 'partial-json-parser'

src/import/trace-event.test.ts

@@ -11,3 +11,11 @@ test('importTraceEvents simple object', async () => {
 test('importTraceEvents multiprocess', async () => {
   await checkProfileSnapshot('./sample/profiles/trace-event/multiprocess.json')
 })
+
+test('importTraceEvents simple partial', async () => {
+  await checkProfileSnapshot('./sample/profiles/trace-event/simple-partial.json')
+})
+
+test('importTraceEvents simple object partial', async () => {
+  await checkProfileSnapshot('./sample/profiles/trace-event/simple-object-partial.json')
+})

src/import/trace-event.ts

@@ -288,10 +288,6 @@ export function isTraceEventFormatted(
   // We're only going to suppor the JSON formatted profiles for now.
   // The spec also discusses support for data embedded in ftrace supported data: https://lwn.net/Articles/365835/.
 
-  // TODO(jlfwong): The spec also specifies that it's valid for the trace to not contain a terminating `]`.
-  // That complicates things a bit for us, so let's just ignore that for now until someone writes in with a
-  // bug report from real data.
-
   return isTraceEventObject(rawProfile) || isTraceEventList(rawProfile)
 }