Add support for formatting Compose YAML files

This feature will not work if the file has clear, syntactical errors
that prevents goccy/go-yaml from parsing the file.

Signed-off-by: Remy Suen <[email protected]>

Author: rcjsuen

CHANGELOG.md

@@ -12,6 +12,8 @@ All notable changes to the Docker Language Server will be documented in this fil
     - improve code completion by automatically including required attributes in completion items ([#155](https://github.com/docker/docker-language-server/issues/155))
   - textDocument/inlayHint
     - show the parent service's value if it is being overridden and they are not object attributes ([#156](https://github.com/docker/docker-language-server/issues/156))
+  - textDocument/formatting
+    - add support to format YAML files that do not have clear syntactical errors ([#165](https://github.com/docker/docker-language-server/issues/165))
 
 ### Fixed
 

README.md

@@ -16,17 +16,20 @@ The Docker Language Server relies on some features that are dependent on [Buildx
   - code completion
   - code navigation
   - document outline support
+  - formatting
   - highlight named references of services, networks, volumes, configs, and secrets
   - hover tooltips
+  - inlay hints for overridden attribute values
   - open links to images
   - rename preparation
   - rename named references
 - Bake files
   - code completion
-  - inferring variable values
-  - formatting
   - code navigation
+  - document outline support
+  - formatting
   - hover tooltips
+  - inferring variable values
 
 ## Installing
 

internal/compose/formatting.go

@@ -0,0 +1,150 @@
+package compose
+
+import (
+	"strings"
+
+	"github.com/docker/docker-language-server/internal/pkg/document"
+	"github.com/docker/docker-language-server/internal/tliron/glsp/protocol"
+	"github.com/sourcegraph/jsonrpc2"
+)
+
+type indentation struct {
+	original int
+	desired  int
+}
+
+type comment struct {
+	line       int
+	whitespace int
+}
+
+func formattingOptionTabSize(options protocol.FormattingOptions) (int, error) {
+	if tabSize, ok := options[protocol.FormattingOptionTabSize].(float64); ok && tabSize > 0 {
+		return int(tabSize), nil
+	}
+	return -1, &jsonrpc2.Error{Code: jsonrpc2.CodeInvalidParams, Message: "tabSize is not a positive integer"}
+}
+
+func indent(indentation int) string {
+	sb := strings.Builder{}
+	for range indentation {
+		sb.WriteString(" ")
+	}
+	return sb.String()
+}
+
+func Formatting(doc document.ComposeDocument, options protocol.FormattingOptions) ([]protocol.TextEdit, error) {
+	file := doc.File()
+	if file == nil || len(file.Docs) == 0 {
+		return nil, nil
+	}
+	tabSize, err := formattingOptionTabSize(options)
+	if err != nil {
+		return nil, err
+	}
+
+	edits := []protocol.TextEdit{}
+	indentations := []indentation{}
+	comments := []comment{}
+	topLevelNodeDetected := false
+	lines := strings.Split(string(doc.Input()), "\n")
+lineCheck:
+	for lineNumber, line := range lines {
+		lineIndentation := 0
+		stop := 0
+		isComment := false
+		empty := true
+		for i := range len(line) {
+			if line[i] == 32 {
+				lineIndentation++
+			} else if line[i] == '#' {
+				empty = false
+				isComment = true
+				comments = append(comments, comment{line: lineNumber, whitespace: i})
+				break
+			} else {
+				empty = false
+				if strings.HasPrefix(lines[lineNumber], "---") {
+					edits = append(edits, formatComments(comments, 0)...)
+					comments = nil
+					indentations = nil
+					topLevelNodeDetected = false
+					continue lineCheck
+				}
+
+				if !topLevelNodeDetected {
+					topLevelNodeDetected = true
+					if lineIndentation > 0 {
+						newIndentation, _ := updateIndentation(indentations, lineIndentation, 0)
+						indentations = append(indentations, newIndentation)
+					}
+				}
+				break
+			}
+			stop++
+		}
+
+		if isComment {
+			continue
+		}
+
+		if lineIndentation != 0 {
+			newIndentation, resetIndex := updateIndentation(indentations, lineIndentation, tabSize)
+			if resetIndex == -1 {
+				indentations = append(indentations, newIndentation)
+			} else {
+				indentations = indentations[:resetIndex+1]
+			}
+			edits = append(edits, formatComments(comments, newIndentation.desired)...)
+			comments = nil
+			if lineIndentation != newIndentation.desired {
+				edits = append(edits, protocol.TextEdit{
+					NewText: indent(newIndentation.desired),
+					Range: protocol.Range{
+						Start: protocol.Position{Line: protocol.UInteger(lineNumber), Character: 0},
+						End:   protocol.Position{Line: protocol.UInteger(lineNumber), Character: protocol.UInteger(stop)},
+					},
+				})
+			}
+		} else if !empty {
+			edits = append(edits, formatComments(comments, 0)...)
+			comments = nil
+			indentations = nil
+		}
+	}
+	return edits, nil
+}
+
+// formatComments goes over the list of comments and corrects its
+// indentation to the desired indentation only if it differs. Any
+// comment that needs to have its indentation changed will have a
+// TextEdit created for it and included in the returned result.
+func formatComments(comments []comment, desired int) []protocol.TextEdit {
+	edits := []protocol.TextEdit{}
+	for _, c := range comments {
+		if desired != c.whitespace {
+			edits = append(edits, protocol.TextEdit{
+				NewText: indent(desired),
+				Range: protocol.Range{
+					Start: protocol.Position{Line: protocol.UInteger(c.line), Character: 0},
+					End:   protocol.Position{Line: protocol.UInteger(c.line), Character: protocol.UInteger(c.whitespace)},
+				},
+			})
+		}
+	}
+	return edits
+}
+
+func updateIndentation(indentations []indentation, original, tabSpacing int) (indentation, int) {
+	last := tabSpacing
+	for i := range indentations {
+		if indentations[i].original == original {
+			return indentations[i], i
+		}
+		last = indentations[i].desired + tabSpacing
+	}
+	return indentation{
+		original: original,
+		desired:  last,
+	}, -1
+}