feat: always print truncated function stderr (#2639)

* feat: always print truncated function stderr

This change makes it so that kpt fn render|eval will always print
truncated stderr output from functions. This is intended to improve the
experience of debugging functions.

* test: add unit test cases for printFnStderr

* test: add e2e test for fn eval stderr

This test case is intended to check that kpt fn eval outputs the stderr
of the function even when the function succeeds. This is doing using a
simple function script which emits hello world to stderr.

* test: add e2e test for fn render stderr

This test case is intended to check that kpt fn render outputs the stderr
of the function even when the function succeeds. This is doing using a
simple function script which emits hello world to stderr.

e2e/testdata/fn-eval/exec-function-stderr/.expected/config.yaml

@@ -0,0 +1,24 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+testType: eval
+stdErr: |
+  [RUNNING] "./function.sh"
+  [PASS] "./function.sh" in 0s
+    Stderr:
+      "Hello world 0!"
+      "Hello world 1!"
+      "Hello world 2!"
+      "Hello world 3!"
+      ...(18 line(s) truncated, use '--truncate-output=false' to disable)

e2e/testdata/fn-eval/exec-function-stderr/.expected/diff.patch

@@ -0,0 +1,21 @@
+diff --git a/resources.yaml b/resources.yaml
+index e8ae6bb..297b99f 100644
+--- a/resources.yaml
++++ b/resources.yaml
+@@ -15,7 +15,7 @@ apiVersion: apps/v1
+ kind: Deployment
+ metadata:
+   name: nginx-deployment
+-  namespace: foo
++  namespace: bar
+ spec:
+   replicas: 3
+ ---
+@@ -23,6 +23,6 @@ apiVersion: custom.io/v1
+ kind: Custom
+ metadata:
+   name: custom
+-  namespace: foo
++  namespace: bar
+ spec:
+   image: nginx:1.2.3

e2e/testdata/fn-eval/exec-function-stderr/.expected/exec.sh

@@ -0,0 +1,19 @@
+#! /bin/bash
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -eo pipefail
+
+kpt fn source \
+  | kpt fn eval --exec ./function.sh

e2e/testdata/fn-eval/exec-function-stderr/.krmignore

@@ -0,0 +1 @@
+.expected

e2e/testdata/fn-eval/exec-function-stderr/function.sh

@@ -0,0 +1,21 @@
+#! /usr/bin/env bash
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+sed -e 's/foo/bar/'
+
+for i in {0..20}
+do
+  >&2 echo "Hello world $i!"
+done

e2e/testdata/fn-eval/exec-function-stderr/resources.yaml

@@ -0,0 +1,28 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-deployment
+  namespace: foo
+spec:
+  replicas: 3
+---
+apiVersion: custom.io/v1
+kind: Custom
+metadata:
+  name: custom
+  namespace: foo
+spec:
+  image: nginx:1.2.3

e2e/testdata/fn-render/exec-function-stderr/.expected/config.yaml

@@ -0,0 +1,24 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+allowExec: true
+stdErr: |
+  [RUNNING] "./testdata/fn-render/exec-function-stderr/function.sh"
+  [PASS] "./testdata/fn-render/exec-function-stderr/function.sh" in 0s
+    Stderr:
+      "Hello world 0!"
+      "Hello world 1!"
+      "Hello world 2!"
+      "Hello world 3!"
+      ...(18 line(s) truncated, use '--truncate-output=false' to disable)

e2e/testdata/fn-render/exec-function-stderr/.expected/diff.patch

@@ -0,0 +1,21 @@
+diff --git a/resources.yaml b/resources.yaml
+index e8ae6bb..297b99f 100644
+--- a/resources.yaml
++++ b/resources.yaml
+@@ -15,7 +15,7 @@ apiVersion: apps/v1
+ kind: Deployment
+ metadata:
+   name: nginx-deployment
+-  namespace: foo
++  namespace: bar
+ spec:
+   replicas: 3
+ ---
+@@ -23,6 +23,6 @@ apiVersion: custom.io/v1
+ kind: Custom
+ metadata:
+   name: custom
+-  namespace: foo
++  namespace: bar
+ spec:
+   image: nginx:1.2.3

e2e/testdata/fn-render/exec-function-stderr/.krmignore

@@ -0,0 +1 @@
+.expected

e2e/testdata/fn-render/exec-function-stderr/Kptfile

@@ -0,0 +1,7 @@
+apiVersion: kpt.dev/v1
+kind: Kptfile
+metadata:
+  name: app
+pipeline:
+  mutators:
+    - exec: "./testdata/fn-render/exec-function-stderr/function.sh"

e2e/testdata/fn-render/exec-function-stderr/function.sh

@@ -0,0 +1,21 @@
+#! /usr/bin/env bash
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+sed -e 's/foo/bar/'
+
+for i in {0..20}
+do
+  >&2 echo "Hello world $i!"
+done

e2e/testdata/fn-render/exec-function-stderr/resources.yaml

@@ -0,0 +1,28 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-deployment
+  namespace: foo
+spec:
+  replicas: 3
+---
+apiVersion: custom.io/v1
+kind: Custom
+metadata:
+  name: custom
+  namespace: foo
+spec:
+  image: nginx:1.2.3

internal/fnruntime/runner.go

@@ -165,6 +165,7 @@ func (fr *FunctionRunner) Filter(input []*yaml.RNode) (output []*yaml.RNode, err
 	if !fr.disableCLIOutput {
 		pr.Printf("[PASS] %q in %v\n", fr.name, time.Since(t0).Truncate(time.Millisecond*100))
 		printFnResult(fr.ctx, fr.fnResult, printer.NewOpt())
+		printFnStderr(fr.ctx, fr.fnResult.Stderr)
 	}
 	return output, err
 }
@@ -345,16 +346,22 @@ func printFnResult(ctx context.Context, fnResult *fnresult.Result, opt *printer.
 // on kpt CLI.
 func printFnExecErr(ctx context.Context, fnErr *ExecError) {
 	pr := printer.FromContextOrDie(ctx)
-	if len(fnErr.Stderr) > 0 {
+	printFnStderr(ctx, fnErr.Stderr)
+	pr.Printf("  Exit code: %d\n\n", fnErr.ExitCode)
+}
+
+// printFnStderr prints given stdErr in a user friendly format on kpt CLI.
+func printFnStderr(ctx context.Context, stdErr string) {
+	pr := printer.FromContextOrDie(ctx)
+	if len(stdErr) > 0 {
 		errLines := &multiLineFormatter{
 			Title:          "Stderr",
-			Lines:          strings.Split(fnErr.Stderr, "\n"),
+			Lines:          strings.Split(stdErr, "\n"),
 			UseQuote:       true,
 			TruncateOutput: printer.TruncateOutput,
 		}
 		pr.Printf("%s", errLines.String())
 	}
-	pr.Printf("  Exit code: %d\n\n", fnErr.ExitCode)
 }
 
 // path (location) of a KRM resources is tracked in a special key in

internal/fnruntime/runner_test.go

@@ -18,12 +18,14 @@ package fnruntime
 
 import (
 	"bytes"
+	"context"
 	"io/ioutil"
 	"os"
 	"path"
 	"strings"
 	"testing"
 
+	"github.com/GoogleContainerTools/kpt/internal/printer"
 	"github.com/GoogleContainerTools/kpt/internal/types"
 	kptfilev1 "github.com/GoogleContainerTools/kpt/pkg/api/kptfile/v1"
 	"github.com/stretchr/testify/assert"
@@ -577,3 +579,70 @@ file:
 		assert.Equal(t, tc.expected, string(out))
 	}
 }
+
+func TestPrintFnStderr(t *testing.T) {
+	tests := map[string]struct {
+		input          string // input
+		truncateOutput bool   // whether to truncate output
+		expected       string // expected result
+	}{
+		"no output": {
+			input:          ``,
+			truncateOutput: true,
+			expected:       ``,
+		},
+		"truncated output": {
+			input: `0
+1
+2
+3
+4
+5`,
+			truncateOutput: true,
+			expected: `  Stderr:
+    "0"
+    "1"
+    "2"
+    "3"
+    ...(2 line(s) truncated, use '--truncate-output=false' to disable)
+`,
+		},
+		"non-truncated output": {
+			input: `0
+1
+2
+3
+4
+5`,
+			truncateOutput: false,
+			expected: `  Stderr:
+    "0"
+    "1"
+    "2"
+    "3"
+    "4"
+    "5"
+`,
+		},
+	}
+	cleanupFunc := func() func() {
+		origTruncateOutput := printer.TruncateOutput
+		return func() {
+			printer.TruncateOutput = origTruncateOutput
+		}
+	}()
+	defer cleanupFunc()
+	for testName, tc := range tests {
+		t.Run(testName, func(t *testing.T) {
+			printer.TruncateOutput = tc.truncateOutput
+			out := &bytes.Buffer{}
+			err := &bytes.Buffer{}
+			ctx := printer.WithContext(context.Background(), printer.New(out, err))
+
+			printFnStderr(ctx, tc.input)
+
+			assert.Equal(t, tc.expected, err.String())
+			assert.Equal(t, "", out.String())
+		})
+	}
+}