fix: error swallowing when using continue (vercel#4354)

### Description

Fixes regression added in vercel#4254 where we swallowed exit codes when
`--continue` was used to invoke turbo.

Don't love this fix, but it was the most straightforward fix I could
see. @mehulkar unsure if I'm handling the case where an execution
summary doesn't have an exit code correctly.

### Testing Instructions

See added integration test and the changed run summary test which now
has a 1 exit code.

cli/integration_tests/basic_monorepo/run_summary/run_summary_fail.t

@@ -8,6 +8,8 @@ Setup
 The maybefails task fails for one workspace but not the other
   $ TURBO_RUN_SUMMARY=true ${TURBO} run maybefails --continue > /dev/null
   my-app:maybefails: command finished with error, but continuing...
+   ERROR  run failed: command  exited (1)
+  [1]
 
 # ExitCode here is 1, because npm will report all errors with exitCode 1
   $ cat $(/bin/ls .turbo/runs/*.json | head -n1) | jq '.tasks | map(select(.taskId == "my-app#maybefails")) | .[0].execution'

cli/integration_tests/monorepo_one_script_error/monorepo/apps/my-app/package.json

@@ -2,6 +2,7 @@
   "name": "my-app",
   "scripts": {
     "okay": "echo 'working'",
+    "okay2": "echo 'working'",
     "error": "exit 2"
   }
 }

cli/integration_tests/monorepo_one_script_error/monorepo/turbo.json

@@ -7,6 +7,10 @@
     },
     "okay": {
       "outputs": []
+    },
+    "okay2": {
+      "dependsOn": ["error"],
+      "outputs": []
     }
   }
 }

cli/integration_tests/monorepo_one_script_error/run.t

@@ -8,13 +8,13 @@ Note that npm reports any failed script as exit code 1, even though we "exit 2"
   \xe2\x80\xa2 Packages in scope: my-app (esc)
   \xe2\x80\xa2 Running error in 1 packages (esc)
   \xe2\x80\xa2 Remote caching disabled (esc)
-  my-app:okay: cache miss, executing 32478bc54ccf0adb
+  my-app:okay: cache miss, executing 62ff444b3068c13b
   my-app:okay: 
   my-app:okay: > okay
   my-app:okay: > echo 'working'
   my-app:okay: 
   my-app:okay: working
-  my-app:error: cache miss, executing 1c682ef8cade4542
+  my-app:error: cache miss, executing 7ec8abd964436064
   my-app:error: 
   my-app:error: > error
   my-app:error: > exit 2
@@ -38,13 +38,13 @@ Make sure error isn't cached
   \xe2\x80\xa2 Packages in scope: my-app (esc)
   \xe2\x80\xa2 Running error in 1 packages (esc)
   \xe2\x80\xa2 Remote caching disabled (esc)
-  my-app:okay: cache hit, replaying output 32478bc54ccf0adb
+  my-app:okay: cache hit, replaying output 62ff444b3068c13b
   my-app:okay: 
   my-app:okay: > okay
   my-app:okay: > echo 'working'
   my-app:okay: 
   my-app:okay: working
-  my-app:error: cache miss, executing 1c682ef8cade4542
+  my-app:error: cache miss, executing 7ec8abd964436064
   my-app:error: 
   my-app:error: > error
   my-app:error: > exit 2
@@ -62,3 +62,38 @@ Make sure error isn't cached
 
    ERROR  run failed: command  exited (1)
   [1]
+
+Make sure error code isn't swallowed with continue
+  $ ${TURBO} okay2 --continue
+  \xe2\x80\xa2 Packages in scope: my-app (esc)
+  \xe2\x80\xa2 Running okay2 in 1 packages (esc)
+  \xe2\x80\xa2 Remote caching disabled (esc)
+  my-app:okay: cache hit, replaying output 62ff444b3068c13b
+  my-app:okay: 
+  my-app:okay: > okay
+  my-app:okay: > echo 'working'
+  my-app:okay: 
+  my-app:okay: working
+  my-app:error: cache miss, executing 7ec8abd964436064
+  my-app:error: 
+  my-app:error: > error
+  my-app:error: > exit 2
+  my-app:error: 
+  my-app:error: npm ERR! Lifecycle script `error` failed with error: 
+  my-app:error: npm ERR! Error: command failed 
+  my-app:error: npm ERR!   in workspace: my-app 
+  my-app:error: npm ERR!   at location: .*apps/my-app  (re)
+  my-app:error: command finished with error, but continuing...
+  my-app:okay2: cache miss, executing 6ec9a564c31e8f12
+  my-app:okay2: 
+  my-app:okay2: > okay2
+  my-app:okay2: > echo 'working'
+  my-app:okay2: 
+  my-app:okay2: working
+
+   Tasks:    2 successful, 3 total
+  Cached:    1 cached, 3 total
+    Time:\s*[\.0-9]+m?s  (re)
+
+   ERROR  run failed: command  exited (1)
+  [1]

cli/internal/run/real_run.go

@@ -150,6 +150,22 @@ func RealRun(
 		base.UI.Error(err.Error())
 	}
 
+	// When continue on error is enabled don't register failed tasks as errors
+	// and instead must inspect the task summaries.
+	if ec.rs.Opts.runOpts.continueOnError {
+		for _, summary := range runSummary.RunSummary.Tasks {
+			if childExit := summary.Execution.ExitCode(); childExit != nil {
+				childExit := *childExit
+				if childExit < 0 {
+					childExit = -childExit
+				}
+				if childExit > exitCode {
+					exitCode = childExit
+				}
+			}
+		}
+	}
+
 	runSummary.Close(exitCode, base.RepoRoot)
 
 	if exitCode != 0 {

cli/internal/runsummary/execution_summary.go

@@ -89,6 +89,16 @@ func (ts *TaskExecutionSummary) MarshalJSON() ([]byte, error) {
 	return json.Marshal(&serializable)
 }
 
+// ExitCode access exit code nil means no exit code was received
+func (ts *TaskExecutionSummary) ExitCode() *int {
+	var exitCode int
+	if ts.exitCode == nil {
+		return nil
+	}
+	exitCode = *ts.exitCode
+	return &exitCode
+}
+
 // executionSummary is the state of the entire `turbo run`. Individual task state in `Tasks` field
 type executionSummary struct {
 	// mu guards reads/writes to the `state` field