bake: fork merged bodies interface logic from hcl repo and use it

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

bake/bake.go

@@ -247,7 +247,7 @@ func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error)
 	}
 
 	if len(hclFiles) > 0 {
-		renamed, err := hclparser.Parse(hcl.MergeFiles(hclFiles), hclparser.Opt{
+		renamed, err := hclparser.Parse(hclparser.MergeFiles(hclFiles), hclparser.Opt{
 			LookupVar:     os.LookupEnv,
 			Vars:          defaults,
 			ValidateLabel: validateTargetName,

bake/hclparser/merged.go

@@ -0,0 +1,233 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+// Forked from https://github.com/hashicorp/hcl/blob/4679383728fe331fc8a6b46036a27b8f818d9bc0/merged.go
+
+package hclparser
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/hcl/v2"
+)
+
+// MergeFiles combines the given files to produce a single body that contains
+// configuration from all of the given files.
+//
+// The ordering of the given files decides the order in which contained
+// elements will be returned. If any top-level attributes are defined with
+// the same name across multiple files, a diagnostic will be produced from
+// the Content and PartialContent methods describing this error in a
+// user-friendly way.
+func MergeFiles(files []*hcl.File) hcl.Body {
+	var bodies []hcl.Body
+	for _, file := range files {
+		bodies = append(bodies, file.Body)
+	}
+	return MergeBodies(bodies)
+}
+
+// MergeBodies is like MergeFiles except it deals directly with bodies, rather
+// than with entire files.
+func MergeBodies(bodies []hcl.Body) hcl.Body {
+	if len(bodies) == 0 {
+		// Swap out for our singleton empty body, to reduce the number of
+		// empty slices we have hanging around.
+		return emptyBody
+	}
+
+	// If any of the given bodies are already merged bodies, we'll unpack
+	// to flatten to a single mergedBodies, since that's conceptually simpler.
+	// This also, as a side-effect, eliminates any empty bodies, since
+	// empties are merged bodies with no inner bodies.
+	var newLen int
+	var flatten bool
+	for _, body := range bodies {
+		if children, merged := body.(mergedBodies); merged {
+			newLen += len(children)
+			flatten = true
+		} else {
+			newLen++
+		}
+	}
+
+	if !flatten { // not just newLen == len, because we might have mergedBodies with single bodies inside
+		return mergedBodies(bodies)
+	}
+
+	if newLen == 0 {
+		// Don't allocate a new empty when we already have one
+		return emptyBody
+	}
+
+	n := make([]hcl.Body, 0, newLen)
+	for _, body := range bodies {
+		if children, merged := body.(mergedBodies); merged {
+			n = append(n, children...)
+		} else {
+			n = append(n, body)
+		}
+	}
+	return mergedBodies(n)
+}
+
+var emptyBody = mergedBodies([]hcl.Body{})
+
+// EmptyBody returns a body with no content. This body can be used as a
+// placeholder when a body is required but no body content is available.
+func EmptyBody() hcl.Body {
+	return emptyBody
+}
+
+type mergedBodies []hcl.Body
+
+// Content returns the content produced by applying the given schema to all
+// of the merged bodies and merging the result.
+//
+// Although required attributes _are_ supported, they should be used sparingly
+// with merged bodies since in this case there is no contextual information
+// with which to return good diagnostics. Applications working with merged
+// bodies may wish to mark all attributes as optional and then check for
+// required attributes afterwards, to produce better diagnostics.
+func (mb mergedBodies) Content(schema *hcl.BodySchema) (*hcl.BodyContent, hcl.Diagnostics) {
+	// the returned body will always be empty in this case, because mergedContent
+	// will only ever call Content on the child bodies.
+	content, _, diags := mb.mergedContent(schema, false)
+	return content, diags
+}
+
+func (mb mergedBodies) PartialContent(schema *hcl.BodySchema) (*hcl.BodyContent, hcl.Body, hcl.Diagnostics) {
+	return mb.mergedContent(schema, true)
+}
+
+func (mb mergedBodies) JustAttributes() (hcl.Attributes, hcl.Diagnostics) {
+	attrs := make(map[string]*hcl.Attribute)
+	var diags hcl.Diagnostics
+
+	for _, body := range mb {
+		thisAttrs, thisDiags := body.JustAttributes()
+
+		if len(thisDiags) != 0 {
+			diags = append(diags, thisDiags...)
+		}
+
+		if thisAttrs != nil {
+			for name, attr := range thisAttrs {
+				if existing := attrs[name]; existing != nil {
+					diags = diags.Append(&hcl.Diagnostic{
+						Severity: hcl.DiagError,
+						Summary:  "Duplicate argument",
+						Detail: fmt.Sprintf(
+							"Argument %q was already set at %s",
+							name, existing.NameRange.String(),
+						),
+						Subject: &attr.NameRange,
+					})
+					continue
+				}
+
+				attrs[name] = attr
+			}
+		}
+	}
+
+	return attrs, diags
+}
+
+func (mb mergedBodies) MissingItemRange() hcl.Range {
+	if len(mb) == 0 {
+		// Nothing useful to return here, so we'll return some garbage.
+		return hcl.Range{
+			Filename: "<empty>",
+		}
+	}
+
+	// arbitrarily use the first body's missing item range
+	return mb[0].MissingItemRange()
+}
+
+func (mb mergedBodies) mergedContent(schema *hcl.BodySchema, partial bool) (*hcl.BodyContent, hcl.Body, hcl.Diagnostics) {
+	// We need to produce a new schema with none of the attributes marked as
+	// required, since _any one_ of our bodies can contribute an attribute value.
+	// We'll separately check that all required attributes are present at
+	// the end.
+	mergedSchema := &hcl.BodySchema{
+		Blocks: schema.Blocks,
+	}
+	for _, attrS := range schema.Attributes {
+		mergedAttrS := attrS
+		mergedAttrS.Required = false
+		mergedSchema.Attributes = append(mergedSchema.Attributes, mergedAttrS)
+	}
+
+	var mergedLeftovers []hcl.Body
+	content := &hcl.BodyContent{
+		Attributes: map[string]*hcl.Attribute{},
+	}
+
+	var diags hcl.Diagnostics
+	for _, body := range mb {
+		var thisContent *hcl.BodyContent
+		var thisLeftovers hcl.Body
+		var thisDiags hcl.Diagnostics
+
+		if partial {
+			thisContent, thisLeftovers, thisDiags = body.PartialContent(mergedSchema)
+		} else {
+			thisContent, thisDiags = body.Content(mergedSchema)
+		}
+
+		if thisLeftovers != nil {
+			mergedLeftovers = append(mergedLeftovers, thisLeftovers)
+		}
+		if len(thisDiags) != 0 {
+			diags = append(diags, thisDiags...)
+		}
+
+		if thisContent.Attributes != nil {
+			for name, attr := range thisContent.Attributes {
+				if existing := content.Attributes[name]; existing != nil {
+					diags = diags.Append(&hcl.Diagnostic{
+						Severity: hcl.DiagError,
+						Summary:  "Duplicate argument",
+						Detail: fmt.Sprintf(
+							"Argument %q was already set at %s",
+							name, existing.NameRange.String(),
+						),
+						Subject: &attr.NameRange,
+					})
+					continue
+				}
+				content.Attributes[name] = attr
+			}
+		}
+
+		if len(thisContent.Blocks) != 0 {
+			content.Blocks = append(content.Blocks, thisContent.Blocks...)
+		}
+	}
+
+	// Finally, we check for required attributes.
+	for _, attrS := range schema.Attributes {
+		if !attrS.Required {
+			continue
+		}
+
+		if content.Attributes[attrS.Name] == nil {
+			// We don't have any context here to produce a good diagnostic,
+			// which is why we warn in the Content docstring to minimize the
+			// use of required attributes on merged bodies.
+			diags = diags.Append(&hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Missing required argument",
+				Detail: fmt.Sprintf(
+					"The argument %q is required, but was not set.",
+					attrS.Name,
+				),
+			})
+		}
+	}
+
+	leftoverBody := MergeBodies(mergedLeftovers)
+	return content, leftoverBody, diags
+}