compile reserved keys to lowercase in IR

ci/release/changelogs/next.md

@@ -3,5 +3,5 @@
 #### Improvements 🧹
 
 #### Bugfixes ⛑️
-
 - Accept absolute paths again on the CLI. [#979](https://github.com/terrastruct/d2/pull/979)
+- Fixes some rare undefined behavior using capitalized reserved keywords [#978](https://github.com/terrastruct/d2/pull/978)

d2compiler/compile_test.go

@@ -285,6 +285,17 @@ containers: {
 `,
 			expErr: `d2/testdata/d2compiler/TestCompile/image_non_style.d2:4:3: image shapes cannot have children.`,
 		},
+		{
+			name: "image_children_Steps",
+
+			text: `x: {
+  icon: https://icons.terrastruct.com/aws/_Group%20Icons/EC2-instance-container_light-bg.svg
+  shape: image
+  Steps
+}
+`,
+			expErr: `d2/testdata/d2compiler/TestCompile/image_children_Steps.d2:4:3: steps is only allowed at a board root`,
+		},
 		{
 			name: "stroke-width",
 

d2ir/compile.go

@@ -1,6 +1,8 @@
 package d2ir
 
 import (
+	"strings"
+
 	"oss.terrastruct.com/d2/d2ast"
 	"oss.terrastruct.com/d2/d2format"
 	"oss.terrastruct.com/d2/d2parser"
@@ -163,13 +165,13 @@ func (c *compiler) compileLink(refctx *RefContext) {
 	}
 
 	// If it doesn't start with one of these reserved words, the link is definitely not a board link.
-	if linkIDA[0] != "layers" && linkIDA[0] != "scenarios" && linkIDA[0] != "steps" && linkIDA[0] != "_" {
+	if !strings.EqualFold(linkIDA[0], "layers") && !strings.EqualFold(linkIDA[0], "scenarios") && !strings.EqualFold(linkIDA[0], "steps") && linkIDA[0] != "_" {
 		return
 	}
 
 	// Chop off the non-board portion of the scope, like if this is being defined on a nested object (e.g. `x.y.z`)
 	for i := len(scopeIDA) - 1; i > 0; i-- {
-		if scopeIDA[i-1] == "layers" || scopeIDA[i-1] == "scenarios" || scopeIDA[i-1] == "steps" {
+		if strings.EqualFold(scopeIDA[i-1], "layers") || strings.EqualFold(scopeIDA[i-1], "scenarios") || strings.EqualFold(scopeIDA[i-1], "steps") {
 			scopeIDA = scopeIDA[:i+1]
 			break
 		}

d2ir/d2ir.go

@@ -655,6 +655,10 @@ func (m *Map) EnsureField(kp *d2ast.KeyPath, refctx *RefContext) (*Field, error)
 func (m *Map) ensureField(i int, kp *d2ast.KeyPath, refctx *RefContext) (*Field, error) {
 	head := kp.Path[i].Unbox().ScalarString()
 
+	if _, ok := d2graph.ReservedKeywords[strings.ToLower(head)]; ok {
+		head = strings.ToLower(head)
+	}
+
 	if head == "_" {
 		return nil, d2parser.Errorf(kp.Path[i].Unbox(), `parent "_" can only be used in the beginning of paths, e.g. "_.x"`)
 	}

testdata/d2compiler/TestCompile/image_children.exp.json

@@ -0,0 +1,12 @@
+{
+  "graph": null,
+  "err": {
+    "ioerr": null,
+    "errs": [
+      {
+        "range": "d2/testdata/d2compiler/TestCompile/image_children.d2,3:2:115-3:3:116",
+        "errmsg": "d2/testdata/d2compiler/TestCompile/image_children.d2:4:3: image shapes cannot have children."
+      }
+    ]
+  }
+}

testdata/d2compiler/TestCompile/image_children_Steps.exp.json

@@ -0,0 +1,12 @@
+{
+  "graph": null,
+  "err": {
+    "ioerr": null,
+    "errs": [
+      {
+        "range": "d2/testdata/d2compiler/TestCompile/image_children_Steps.d2,3:2:115-3:7:120",
+        "errmsg": "d2/testdata/d2compiler/TestCompile/image_children_Steps.d2:4:3: steps is only allowed at a board root"
+      }
+    ]
+  }
+}