Allow collapsed stacks with invalid lines (#336)

Ingest files containing collapsed stacks and tolerate invalid lines,
like FlameGraph does.

Some files might contain lines starting with a # to add comments to the
collected samples. Speedscope should still attempt to parse these files
as collapsed stacks and only keep the samples that it can find. Only
fail if there are no samples reported.

sample/profiles/stackcollapse/simple-with-invalids.txt

@@ -0,0 +1,8 @@
+# comment that gives extra info about the samples
+// some other comment
+a;b;c 1
+a;b;c 1
+a;b;d 4
+a;b;c 3
+a;b 5
+invalid line

src/import/__snapshots__/bg-flamegraph.test.ts.snap

@@ -212,6 +212,60 @@ exports[`importFromBGFlameGraph with UTF-16, Little Endian: indexToView 1`] = `0
 
 exports[`importFromBGFlameGraph with UTF-16, Little Endian: profileGroup.name 1`] = `"simple-utf16-le.txt"`;
 
+exports[`importFromBGFlameGraph with invalid lines 1`] = `
+Object {
+  "frames": Array [
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "a",
+      "line": undefined,
+      "name": "a",
+      "selfWeight": 0,
+      "totalWeight": 14,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "b",
+      "line": undefined,
+      "name": "b",
+      "selfWeight": 5,
+      "totalWeight": 14,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "c",
+      "line": undefined,
+      "name": "c",
+      "selfWeight": 5,
+      "totalWeight": 5,
+    },
+    Frame {
+      "col": undefined,
+      "file": undefined,
+      "key": "d",
+      "line": undefined,
+      "name": "d",
+      "selfWeight": 4,
+      "totalWeight": 4,
+    },
+  ],
+  "name": "simple-with-invalids.txt",
+  "stacks": Array [
+    "a;b;c 2",
+    "a;b;d 4",
+    "a;b;c 3",
+    "a;b 5",
+  ],
+}
+`;
+
+exports[`importFromBGFlameGraph with invalid lines: indexToView 1`] = `0`;
+
+exports[`importFromBGFlameGraph with invalid lines: profileGroup.name 1`] = `"simple-with-invalids.txt"`;
+
 exports[`importFromBGFlameGraph: indexToView 1`] = `0`;
 
 exports[`importFromBGFlameGraph: profileGroup.name 1`] = `"simple.txt"`;

src/import/bg-flamegraph.test.ts

@@ -15,3 +15,7 @@ test('importFromBGFlameGraph with UTF-16, Little Endian', async () => {
 test('importFromBGFlameGraph with UTF-16, Big Endian', async () => {
   await checkProfileSnapshot('./sample/profiles/stackcollapse/simple-utf16-be.txt')
 })
+
+test('importFromBGFlameGraph with invalid lines', async () => {
+  await checkProfileSnapshot('./sample/profiles/stackcollapse/simple-with-invalids.txt')
+})

src/import/index.ts

@@ -201,19 +201,17 @@ async function _importProfileGroup(dataSource: ProfileDataSource): Promise<Profi
       return toGroup(importFromInstrumentsDeepCopy(contents))
     }
 
-    // If every line ends with a space followed by a number, it's probably
-    // the collapsed stack format.
-    const lineCount = contents.split(/\n/).length
-    if (lineCount >= 1 && lineCount === contents.split(/ \d+\r?\n/).length) {
-      console.log('Importing as collapsed stack format')
-      return toGroup(importFromBGFlameGraph(contents))
-    }
-
     const fromLinuxPerf = importFromLinuxPerf(contents)
     if (fromLinuxPerf) {
       console.log('Importing from linux perf script output')
       return fromLinuxPerf
     }
+
+    const fromBGFlameGraph = importFromBGFlameGraph(contents)
+    if (fromBGFlameGraph) {
+      console.log('Importing as collapsed stack format')
+      return toGroup(fromBGFlameGraph)
+    }
   }
 
   // Unrecognized format