ref: Extract source context + tests (#2376)

Author: HazAT

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- [utils] ref: Extract adding source context incl. tests
+
 ## 5.11.0
 
 - [apm] fix: Always attach `contexts.trace` to finished transaction (#2353)

packages/node/src/parsers.ts

@@ -1,5 +1,5 @@
 import { Event, Exception, ExtendedError, StackFrame } from '@sentry/types';
-import { basename, dirname, snipLine, SyncPromise } from '@sentry/utils';
+import { addContextToFrame, basename, dirname, SyncPromise } from '@sentry/utils';
 import { readFile } from 'fs';
 import { LRUMap } from 'lru_map';
 
@@ -203,15 +203,7 @@ function addPrePostContext(
           try {
             const lines = (sourceFiles[frame.filename] as string).split('\n');
 
-            frame.pre_context = lines
-              .slice(Math.max(0, (frame.lineno || 0) - (linesOfContext + 1)), (frame.lineno || 0) - 1)
-              .map((line: string) => snipLine(line, 0));
-
-            frame.context_line = snipLine(lines[(frame.lineno || 0) - 1], frame.colno || 0);
-
-            frame.post_context = lines
-              .slice(frame.lineno || 0, (frame.lineno || 0) + linesOfContext)
-              .map((line: string) => snipLine(line, 0));
+            addContextToFrame(lines, frame, linesOfContext);
           } catch (e) {
             // anomaly, being defensive in case
             // unlikely to ever happen in practice but can definitely happen in theory

packages/utils/src/misc.ts

@@ -1,6 +1,7 @@
-import { Event, Integration, WrappedFunction } from '@sentry/types';
+import { Event, Integration, StackFrame, WrappedFunction } from '@sentry/types';
 
 import { isString } from './is';
+import { snipLine } from './string';
 
 /** Internal */
 interface SentryGlobal {
@@ -426,3 +427,26 @@ export function getFunctionName(fn: unknown): string {
     return defaultFunctionName;
   }
 }
+
+/**
+ * This function adds context (pre/post/line) lines to the provided frame
+ *
+ * @param lines string[] containing all lines
+ * @param frame StackFrame that will be mutated
+ * @param linesOfContext number of context lines we want to add pre/post
+ */
+export function addContextToFrame(lines: string[], frame: StackFrame, linesOfContext: number = 5): void {
+  const lineno = frame.lineno || 0;
+  const maxLines = lines.length;
+  const sourceLine = Math.max(Math.min(maxLines, lineno - 1), 0);
+
+  frame.pre_context = lines
+    .slice(Math.max(0, sourceLine - linesOfContext), sourceLine)
+    .map((line: string) => snipLine(line, 0));
+
+  frame.context_line = snipLine(lines[Math.min(maxLines - 1, sourceLine)], frame.colno || 0);
+
+  frame.post_context = lines
+    .slice(Math.min(sourceLine + 1, maxLines), sourceLine + 1 + linesOfContext)
+    .map((line: string) => snipLine(line, 0));
+}

packages/utils/test/misc.test.ts

@@ -1,4 +1,6 @@
-import { getEventDescription, getGlobalObject, parseRetryAfterHeader } from '../src/misc';
+import { StackFrame } from '@sentry/types';
+
+import { addContextToFrame, getEventDescription, getGlobalObject, parseRetryAfterHeader } from '../src/misc';
 
 describe('getEventDescription()', () => {
   test('message event', () => {
@@ -139,3 +141,72 @@ describe('parseRetryAfterHeader', () => {
     ).toEqual(13 * 1000);
   });
 });
+
+describe('addContextToFrame', () => {
+  const lines = [
+    '1: a',
+    '2: b',
+    '3: c',
+    '4: d',
+    '5: e',
+    '6: f',
+    '7: g',
+    '8: h',
+    '9: i',
+    '10: j',
+    '11: k',
+    '12: l',
+    '13: m',
+    '14: n',
+  ];
+
+  test('start of file', () => {
+    const frame: StackFrame = {
+      lineno: 0,
+    };
+    addContextToFrame(lines, frame);
+    expect(frame.pre_context).toEqual([]);
+    expect(frame.context_line).toEqual('1: a');
+    expect(frame.post_context).toEqual(['2: b', '3: c', '4: d', '5: e', '6: f']);
+  });
+
+  test('mid of file', () => {
+    const frame: StackFrame = {
+      lineno: 4,
+    };
+    addContextToFrame(lines, frame);
+    expect(frame.pre_context).toEqual(['1: a', '2: b', '3: c']);
+    expect(frame.context_line).toEqual('4: d');
+    expect(frame.post_context).toEqual(['5: e', '6: f', '7: g', '8: h', '9: i']);
+  });
+
+  test('end of file', () => {
+    const frame: StackFrame = {
+      lineno: 14,
+    };
+    addContextToFrame(lines, frame);
+    expect(frame.pre_context).toEqual(['9: i', '10: j', '11: k', '12: l', '13: m']);
+    expect(frame.context_line).toEqual('14: n');
+    expect(frame.post_context).toEqual([]);
+  });
+
+  test('negative', () => {
+    const frame: StackFrame = {
+      lineno: -1,
+    };
+    addContextToFrame(lines, frame);
+    expect(frame.pre_context).toEqual([]);
+    expect(frame.context_line).toEqual('1: a');
+    expect(frame.post_context).toEqual(['2: b', '3: c', '4: d', '5: e', '6: f']);
+  });
+
+  test('overshoot', () => {
+    const frame: StackFrame = {
+      lineno: 999,
+    };
+    addContextToFrame(lines, frame);
+    expect(frame.pre_context).toEqual(['10: j', '11: k', '12: l', '13: m', '14: n']);
+    expect(frame.context_line).toEqual('14: n');
+    expect(frame.post_context).toEqual([]);
+  });
+});