Provide passive per-source resource contexts

internal/engine/source_context.go

@@ -0,0 +1,112 @@
+package engine
+
+import (
+	"io/fs"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+func contextsForAcquiredSources(source Source, context *FilesystemContext, baseSource *SourceInfo, sources []SourceInfo) (map[string]ResourceContext, *Diagnostic) {
+	if len(sources) == 0 {
+		return nil, nil
+	}
+	var rootPath, basePath string
+	var filesystem fs.FS
+	if source.kind == sourceFilesystem {
+		filesystem = source.namespace.filesystem
+		rootPath, basePath = ".", path.Dir(source.path)
+		if context != nil && context.Root != "" {
+			rootPath = context.Root
+		}
+	} else if context != nil && context.FS != nil {
+		filesystem = context.FS.namespace.filesystem
+		rootPath, basePath = context.Root, context.BaseDir
+	} else if source.kind == sourceFile {
+		filePath := sources[0].Path
+		if baseSource != nil {
+			filePath = baseSource.Path
+		}
+		basePath = filepath.Dir(filePath)
+		rootPath = basePath
+		if context != nil && context.Root != "" {
+			canonical, err := canonicalExistingPath(context.Root)
+			if err != nil {
+				value := importDiagnostic(CodeImportInvalid, "configuration root could not be canonicalized", nil)
+				return nil, &value
+			}
+			rootPath = canonical
+		}
+	} else if context != nil {
+		var err error
+		rootPath, err = canonicalExistingPath(context.Root)
+		if err != nil {
+			value := importDiagnostic(CodeImportInvalid, "configuration root could not be canonicalized", nil)
+			return nil, &value
+		}
+		basePath, err = canonicalExistingPath(context.BaseDir)
+		if err != nil {
+			value := importDiagnostic(CodeImportInvalid, "import base directory could not be canonicalized", nil)
+			return nil, &value
+		}
+	} else {
+		return nil, nil
+	}
+	var rooted fs.FS
+	if filesystem != nil {
+		rooted = rootedNativeFS{filesystem: filesystem, root: rootPath}
+	} else {
+		rooted = rootedHostFS{root: rootPath}
+	}
+	result := make(map[string]ResourceContext, len(sources))
+	for _, acquired := range sources {
+		base := basePath
+		if acquired.Path != "" {
+			if filesystem != nil {
+				base = path.Dir(acquired.Path)
+			} else {
+				base = filepath.Dir(acquired.Path)
+			}
+		}
+		var relative string
+		if filesystem != nil {
+			if !fs.ValidPath(rootPath) || !fs.ValidPath(base) || rootPath != "." && base != rootPath && !strings.HasPrefix(base, rootPath+"/") {
+				value := importDiagnostic(CodeImportOutsideRoot, "source base is outside the configuration root", nil)
+				return nil, &value
+			}
+			relative = base
+			if rootPath != "." {
+				relative = strings.TrimPrefix(strings.TrimPrefix(base, rootPath), "/")
+				if relative == "" {
+					relative = "."
+				}
+			}
+		} else {
+			if !containedPath(rootPath, base) {
+				value := importDiagnostic(CodeImportOutsideRoot, "source base is outside the configuration root", nil)
+				return nil, &value
+			}
+			var err error
+			relative, err = filepath.Rel(rootPath, base)
+			if err != nil {
+				value := importDiagnostic(CodeImportInvalid, "source base could not be addressed in the configuration root", nil)
+				return nil, &value
+			}
+			relative = filepath.ToSlash(relative)
+		}
+		result[acquired.ID] = ResourceContext{FS: rooted, BaseDir: relative}
+	}
+	return result, nil
+}
+
+func mergeResourceContexts(target *map[string]ResourceContext, incoming map[string]ResourceContext) {
+	if len(incoming) == 0 {
+		return
+	}
+	if *target == nil {
+		*target = make(map[string]ResourceContext, len(incoming))
+	}
+	for id, context := range incoming {
+		(*target)[id] = context
+	}
+}