d2cli: Pass path for imports correctly

d2cli/main.go

@@ -322,6 +322,7 @@ func compile(ctx context.Context, ms *xmain.State, plugin d2plugin.Plugin, rende
 		Ruler:      ruler,
 		ThemeID:    renderOpts.ThemeID,
 		FontFamily: fontFamily,
+		InputPath:  inputPath,
 	}
 	if renderOpts.Sketch {
 		opts.FontFamily = go2.Pointer(d2fonts.HandDrawn)

d2compiler/compile.go

@@ -28,7 +28,7 @@ type CompileOptions struct {
 	FS fs.FS
 }
 
-func Compile(path string, r io.RuneReader, opts *CompileOptions) (*d2graph.Graph, error) {
+func Compile(p string, r io.RuneReader, opts *CompileOptions) (*d2graph.Graph, error) {
 	if opts == nil {
 		opts = &CompileOptions{}
 	}
@@ -36,7 +36,7 @@ func Compile(path string, r io.RuneReader, opts *CompileOptions) (*d2graph.Graph
 		opts.FS = os.DirFS("/")
 	}
 
-	ast, err := d2parser.Parse(path, r, &d2parser.ParseOptions{
+	ast, err := d2parser.Parse(p, r, &d2parser.ParseOptions{
 		UTF16: opts.UTF16,
 	})
 	if err != nil {

d2ir/import.go

@@ -2,6 +2,7 @@ package d2ir
 
 import (
 	"bufio"
+	"os"
 	"path"
 	"strings"
 
@@ -82,7 +83,25 @@ func (c *compiler) __import(imp *d2ast.Import) (*Map, bool) {
 		return ir, true
 	}
 
-	f, err := c.fs.Open(impPath)
+	p := path.Clean(impPath)
+	if path.IsAbs(p) {
+		// Path cannot be absolute. DirFS does not accept absolute paths. We strip off the leading
+		// slash to make it relative to the root.
+		p = p[1:]
+	} else if c.fs == os.DirFS("/") {
+		wd, err := os.Getwd()
+		if err != nil {
+			c.errorf(imp, "failed to import %q: %v", impPath, err)
+			return nil, false
+		}
+		p = path.Join(wd, p)
+		// See above explanation.
+		if path.IsAbs(p) {
+			p = p[1:]
+		}
+	}
+
+	f, err := c.fs.Open(p)
 	if err != nil {
 		c.errorf(imp, "failed to import %q: %v", impPath, err)
 		return nil, false

d2lib/d2.go

@@ -31,6 +31,8 @@ type CompileOptions struct {
 	// - pre-measured (web setting)
 	// TODO maybe some will want to configure code font too, but that's much lower priority
 	FontFamily *d2fonts.FontFamily
+
+	InputPath string
 }
 
 func Compile(ctx context.Context, input string, opts *CompileOptions) (*d2target.Diagram, *d2graph.Graph, error) {
@@ -38,7 +40,7 @@ func Compile(ctx context.Context, input string, opts *CompileOptions) (*d2target
 		opts = &CompileOptions{}
 	}
 
-	g, err := d2compiler.Compile("", strings.NewReader(input), &d2compiler.CompileOptions{
+	g, err := d2compiler.Compile(opts.InputPath, strings.NewReader(input), &d2compiler.CompileOptions{
 		UTF16: opts.UTF16,
 	})
 	if err != nil {