From cdccc5a4399987a5a37f2a823f99753bbfc8824d Mon Sep 17 00:00:00 2001
From: Paul Jolly <paul@myitcv.io>
Date: Tue, 19 Sep 2023 21:29:18 +0100
Subject: [PATCH] preprocessor: add support for code directive

A code directive is a txtar-based directive, that contains a single
file. It results in a ```-block, with the language of that block taken
from the extension of the single file in the txtar archive. The basename
of the file is irrelevant. The contents of the code directive are
formatted, unless the #nofmt tag is used.

Preprocessor-No-Write-Cache: true
Signed-off-by: Paul Jolly <paul@myitcv.io>
Change-Id: If68a9b0a10a2224e8841dfed73867fd41837b584
Dispatch-Trailer: {"type":"trybot","CL":1169683,"patchset":1,"ref":"refs/changes/83/1169683/1","targetBranch":"alpha"}
---
 internal/cmd/preprocessor/cmd/code_node.go    | 84 +++++++++++++++++++
 internal/cmd/preprocessor/cmd/parse.go        |  6 ++
 internal/cmd/preprocessor/cmd/rootfile.go     |  1 +
 .../cmd/testdata/execute_transform.txtar      |  7 ++
 4 files changed, 98 insertions(+)
 create mode 100644 internal/cmd/preprocessor/cmd/code_node.go

diff --git a/internal/cmd/preprocessor/cmd/code_node.go b/internal/cmd/preprocessor/cmd/code_node.go
new file mode 100644
index 000000000..c66845b1f
--- /dev/null
+++ b/internal/cmd/preprocessor/cmd/code_node.go
@@ -0,0 +1,84 @@
+// Copyright 2023 The CUE Authors
+//
+// 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.
+
+package cmd
+
+import (
+	"bytes"
+	"fmt"
+)
+
+const (
+	fnCode = "code"
+)
+
+// A codeNode is used to create a simple ```-based code block for a single file
+// whose contents are formatted. This ensures good formatting but also valid
+// code.
+type codeNode struct {
+	txtarNode
+}
+
+func (c *codeNode) nodeType() string {
+	return fnCode
+}
+
+var _ runnableNode = (*codeNode)(nil)
+
+type codeNodeRunContext struct {
+	*txtarRunContext
+}
+
+func (s *codeNode) validate() error {
+	if l := len(s.analysis.fileNames); l != 1 {
+		return fmt.Errorf("code nodes can only contain one file in the txtar archive")
+	}
+	return nil
+}
+
+func (s *codeNode) run() runnable {
+	return &codeNodeRunContext{
+		txtarRunContext: &txtarRunContext{
+			txtarNode:        s.txtarNode,
+			executionContext: s.executionContext,
+			bufferedErrorContext: &errorContextBuffer{
+				executionContext: s.executionContext,
+			},
+		},
+	}
+}
+
+func (s *codeNodeRunContext) run() (err error) {
+	defer recoverFatalError(&err)
+
+	if err := s.formatFiles(); err != nil {
+		return errorIfInError(s)
+	}
+
+	return nil
+}
+
+func (s *codeNode) writeTransformTo(b *bytes.Buffer) error {
+	p := bufPrintf(b)
+
+	// There will only be one file
+	a := s.analysis.fileNames[0]
+	f := s.effectiveArchive.Files[0]
+
+	// TODO tidy up templating etc
+	p("```%s\n", a.Language)
+	p("%s", f.Data)
+	p("```")
+	return nil
+}
diff --git a/internal/cmd/preprocessor/cmd/parse.go b/internal/cmd/preprocessor/cmd/parse.go
index 3ce4d60a4..6c092a636 100644
--- a/internal/cmd/preprocessor/cmd/parse.go
+++ b/internal/cmd/preprocessor/cmd/parse.go
@@ -192,6 +192,12 @@ func (rf *rootFile) parse_WithNode(n *parse.WithNode) (node, error) {
 			return nil, err
 		}
 		return &sidebysideNode{txtarNode: t}, nil
+	case fnCode:
+		t, err := rf.parse_txtarNode(n, fn.Ident, c.Args[1:])
+		if err != nil {
+			return nil, err
+		}
+		return &codeNode{txtarNode: t}, nil
 	case fnStep:
 		// Increment first because we are numbering from 1
 		rf.stepNumber++
diff --git a/internal/cmd/preprocessor/cmd/rootfile.go b/internal/cmd/preprocessor/cmd/rootfile.go
index 8968ab661..186f1f52a 100644
--- a/internal/cmd/preprocessor/cmd/rootfile.go
+++ b/internal/cmd/preprocessor/cmd/rootfile.go
@@ -43,6 +43,7 @@ var (
 	// were function calls.
 	templateFunctions = map[string]any{
 		fnSidebyside: true,
+		fnCode:       true,
 		fnStep:       true,
 		fnUpload:     true,
 		fnScript:     true,
diff --git a/internal/cmd/preprocessor/cmd/testdata/execute_transform.txtar b/internal/cmd/preprocessor/cmd/testdata/execute_transform.txtar
index 9dadd9dfd..d73c003b2 100644
--- a/internal/cmd/preprocessor/cmd/testdata/execute_transform.txtar
+++ b/internal/cmd/preprocessor/cmd/testdata/execute_transform.txtar
@@ -65,6 +65,10 @@ package site
 >
 >{{{with step}}}
 >some text
+>{{{with code "en" "x.cue example"}}}
+>-- x.cue --
+>x: 5
+>{{{end}}}
 >{{{end}}}
 >
 >Some text after
@@ -98,6 +102,9 @@ map: {
 
 {{< step stepNumber="2" >}}
 some text
+```text
+x: 5
+```
 {{< /step >}}
 
 Some text after