Conditional execution of steps with if: (#520)

This extends the schema of the batch spec `steps` to add a new field:

- `if: <string that can use templating to evaluate to "true" or "false">`

(the corresponding schema changes `sourcegraph/sourcegraph` are here: https://github.com/sourcegraph/sourcegraph/pull/20399)

`if:` is evaluated in a best-effort partial-evaluation manner before the execution of the `steps`. If we can statically evaluate it, we use the result of that evaluation to build a per-repository/per-workspace list of tasks, which increases cache utilisation.

See the comments in `partial_eval.go` for more details.

It also extends the `StepContext` in the templates to have the `steps.{added,modified,deleted}_files` and `steps.path` fields.

Author: mrnugget

CHANGELOG.md

@@ -13,6 +13,8 @@ All notable changes to `src-cli` are documented in this file.
 
 ### Added
 
+- Starting with Sourcegraph 3.28.0 batch spec `steps` can contain an `if: <template string>` attribute that determines whether the given step will be executed. [#520](https://github.com/sourcegraph/src-cli/pull/520)
+
 ### Changed
 
 ### Fixed

cmd/src/batch_common.go

@@ -201,6 +201,7 @@ type executeBatchSpecOpts struct {
 // Sourcegraph, including execution as needed and applying the resulting batch
 // spec if specified.
 func executeBatchSpec(ctx context.Context, opts executeBatchSpecOpts) error {
+	batches.DebugOut = opts.out
 	svc := service.New(&service.Opts{
 		AllowUnsupported: opts.flags.allowUnsupported,
 		AllowIgnored:     opts.flags.allowIgnored,
@@ -285,11 +286,15 @@ func executeBatchSpec(ctx context.Context, opts executeBatchSpecOpts) error {
 	}
 
 	pending = batchCreatePending(opts.out, "Determining workspaces")
-	tasks, err := svc.BuildTasks(ctx, repos, batchSpec)
+	tb, err := executor.NewTaskBuilder(batchSpec, svc)
 	if err != nil {
-		return errors.Wrap(err, "Calculating execution plan")
+		return errors.Wrap(err, "Parsing batch spec to determine workspaces")
 	}
-	batchCompletePending(pending, fmt.Sprintf("Found %d workspaces", len(tasks)))
+	tasks, err := tb.BuildAll(ctx, repos)
+	if err != nil {
+		return err
+	}
+	batchCompletePending(pending, fmt.Sprintf("Found %d workspaces with steps to execute", len(tasks)))
 
 	execOpts := executor.Opts{
 		CacheDir:    opts.flags.cacheDir,

internal/batches/batch_spec.go

@@ -94,9 +94,25 @@ type Step struct {
 	Files     map[string]string `json:"files,omitempty" yaml:"files,omitempty"`
 	Outputs   Outputs           `json:"outputs,omitempty" yaml:"outputs,omitempty"`
 
+	If interface{} `json:"if,omitempty" yaml:"if,omitempty"`
+
 	image docker.Image
 }
 
+func (s *Step) IfCondition() string {
+	switch v := s.If.(type) {
+	case bool:
+		if v {
+			return "true"
+		}
+		return "false"
+	case string:
+		return v
+	default:
+		return ""
+	}
+}
+
 func (s *Step) SetImage(image docker.Image) {
 	s.image = image
 }
@@ -178,6 +194,17 @@ func ParseBatchSpec(data []byte, features FeatureFlags) (*BatchSpec, error) {
 		errs = multierror.Append(errs, errors.New("batch spec includes workspaces, which is not supported in this Sourcegraph version"))
 	}
 
+	if !features.AllowConditionalExec {
+		for i, step := range spec.Steps {
+			if step.IfCondition() != "" {
+				errs = multierror.Append(errs, fmt.Errorf(
+					"step %d in batch spec uses the 'if' attribute for conditional execution, which is not supported in this Sourcegraph version",
+					i+1,
+				))
+			}
+		}
+	}
+
 	return &spec, errs.ErrorOrNil()
 }
 

internal/batches/batch_spec_test.go

@@ -1,6 +1,9 @@
 package batches
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func TestParseBatchSpec(t *testing.T) {
 	t.Run("valid", func(t *testing.T) {
@@ -87,4 +90,84 @@ changesetTemplate:
 			t.Fatalf("wrong error. want=%q, have=%q", wantErr, haveErr)
 		}
 	})
+
+	t.Run("uses unsupported conditional exec", func(t *testing.T) {
+		const spec = `
+name: hello-world
+description: Add Hello World to READMEs
+on:
+  - repositoriesMatchingQuery: file:README.md
+steps:
+  - run: echo Hello World | tee -a $(find -name README.md)
+    if: "false"
+    container: alpine:3
+
+changesetTemplate:
+  title: Hello World
+  body: My first batch change!
+  branch: hello-world
+  commit:
+    message: Append Hello World to all README.md files
+  published: false
+`
+
+		_, err := ParseBatchSpec([]byte(spec), FeatureFlags{})
+		if err == nil {
+			t.Fatal("no error returned")
+		}
+
+		wantErr := `1 error occurred:
+	* step 1 in batch spec uses the 'if' attribute for conditional execution, which is not supported in this Sourcegraph version
+
+`
+		haveErr := err.Error()
+		if haveErr != wantErr {
+			t.Fatalf("wrong error. want=%q, have=%q", wantErr, haveErr)
+		}
+	})
+
+	t.Run("parsing if attribute", func(t *testing.T) {
+		const specTemplate = `
+name: hello-world
+description: Add Hello World to READMEs
+on:
+  - repositoriesMatchingQuery: file:README.md
+steps:
+  - run: echo Hello World | tee -a $(find -name README.md)
+    if: %s
+    container: alpine:3
+
+changesetTemplate:
+  title: Hello World
+  body: My first batch change!
+  branch: hello-world
+  commit:
+    message: Append Hello World to all README.md files
+  published: false
+`
+
+		for _, tt := range []struct {
+			raw  string
+			want string
+		}{
+			{raw: `"true"`, want: "true"},
+			{raw: `"false"`, want: "false"},
+			{raw: `true`, want: "true"},
+			{raw: `false`, want: "false"},
+			{raw: `"${{ foobar }}"`, want: "${{ foobar }}"},
+			{raw: `${{ foobar }}`, want: "${{ foobar }}"},
+			{raw: `foobar`, want: "foobar"},
+		} {
+			spec := fmt.Sprintf(specTemplate, tt.raw)
+			batchSpec, err := ParseBatchSpec([]byte(spec), FeatureFlags{AllowConditionalExec: true})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			fmt.Printf("len(batchSpec.Steps)=%d", len(batchSpec.Steps))
+			if batchSpec.Steps[0].IfCondition() != tt.want {
+				t.Fatalf("wrong IfCondition. want=%q, got=%q", tt.want, batchSpec.Steps[0].IfCondition())
+			}
+		}
+	})
 }

internal/batches/debug.go

@@ -1,6 +1,8 @@
 package batches
 
-import "github.com/sourcegraph/sourcegraph/lib/output"
+import (
+	"github.com/sourcegraph/sourcegraph/lib/output"
+)
 
 // DebugOut can be used to print debug messages in development to the TUI.
 // For that it needs to be set to an actual *output.Output.

internal/batches/executor/executor_test.go

@@ -305,7 +305,6 @@ output4=integration-test-batch-change`,
 			wantAuthorName:    "myOutputName1=main.go",
 			wantAuthorEmail:   "myOutputName1=main.go",
 		},
-
 		{
 			name: "workspaces",
 			archives: []mock.RepoArchive{
@@ -374,6 +373,40 @@ output4=integration-test-batch-change`,
 				},
 			},
 		},
+		{
+			name: "step condition",
+			archives: []mock.RepoArchive{
+				{Repo: srcCLIRepo, Files: map[string]string{
+					"README.md": "# Welcome to the README\n",
+				}},
+				{Repo: sourcegraphRepo, Files: map[string]string{
+					"README.md": "# Sourcegraph README\n",
+				}},
+			},
+			steps: []batches.Step{
+				{Run: `echo -e "foobar\n" >> README.md`},
+				{
+					Run: `echo "foobar" >> hello.txt`,
+					If:  `${{ matches repository.name "github.com/sourcegraph/sourcegra*" }}`,
+				},
+				{
+					Run: `echo "foobar" >> in-path.txt`,
+					If:  `${{ matches steps.path "sub/directory/of/repo" }}`,
+				},
+			},
+			tasks: []*Task{
+				{Repository: srcCLIRepo},
+				{Repository: sourcegraphRepo, Path: "sub/directory/of/repo"},
+			},
+			wantFilesChanged: filesByRepository{
+				srcCLIRepo.ID: filesByBranch{
+					changesetTemplateBranch: []string{"README.md"},
+				},
+				sourcegraphRepo.ID: {
+					changesetTemplateBranch: []string{"README.md", "hello.txt", "in-path.txt"},
+				},
+			},
+		},
 	}
 
 	for _, tc := range tests {
@@ -949,5 +982,6 @@ func featuresAllEnabled() batches.FeatureFlags {
 		UseGzipCompression:       true,
 		AllowTransformChanges:    true,
 		AllowWorkspaces:          true,
+		AllowConditionalExec:     true,
 	}
 }