Fix errors with strict lookup in compat mode

Fixes #2149, fixes #1741

Author: theodorejb

lib/handlebars/compiler/javascript-compiler.js

@@ -1175,20 +1175,34 @@ function strictLookup(requireTerminal, compiler, parts, startPartIndex, type) {
     stack = compiler.nameLookup(stack, parts[i], type);
   }
 
-  if (requireTerminal) {
+  if (!requireTerminal) {
+    return stack;
+  }
+
+  if (startPartIndex > len) {
+    // Compat mode already consumed all parts via depthedLookup; the stack
+    // holds the resolved value, not an object to look the property up on.
+    // Use container.strictLookup to traverse depths with a strict error on miss.
     return [
-      compiler.aliasable('container.strict'),
-      '(',
-      stack,
-      ', ',
+      compiler.aliasable('container.strictLookup'),
+      '(depths, ',
       compiler.quotedString(parts[len]),
       ', ',
       JSON.stringify(compiler.source.currentLocation),
       ' )',
     ];
-  } else {
-    return stack;
   }
+
+  return [
+    compiler.aliasable('container.strict'),
+    '(',
+    stack,
+    ', ',
+    compiler.quotedString(parts[len]),
+    ', ',
+    JSON.stringify(compiler.source.currentLocation),
+    ' )',
+  ];
 }
 
 export default JavaScriptCompiler;

lib/handlebars/runtime.js

@@ -116,6 +116,22 @@ export function template(templateSpec, env) {
       }
       return container.lookupProperty(obj, name);
     },
+    strictLookup: function (depths, name, loc) {
+      const len = depths.length;
+      let depth;
+      for (let i = 0; i < len; i++) {
+        const d = depths[i];
+        if (
+          d &&
+          (typeof d === 'object' || typeof d === 'function') &&
+          name in d
+        ) {
+          depth = d;
+          break;
+        }
+      }
+      return container.strict(depth, name, loc);
+    },
     lookupProperty: function (parent, propertyName) {
       if (Utils.isMap(parent)) {
         return parent.get(propertyName);

spec/strict.js

@@ -121,6 +121,63 @@ describe('strict', function () {
     });
   });
 
+  describe('strict and compat mode', function () {
+    it('GH-1741: should render a simple variable', function () {
+      expectTemplate('{{v}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ v: 'a' })
+        .toCompileTo('a');
+    });
+
+    it('should throw for a missing variable', function () {
+      expectTemplate('{{v}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .toThrow(Exception, /"v" not defined in/);
+    });
+
+    it('GH-2149: should render correctly when block context is a boolean', function () {
+      expectTemplate('{{#foo}}Hello {{bar}}{{/foo}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ foo: true, bar: 'World' })
+        .toCompileTo('Hello World');
+    });
+
+    it('GH-2149: should render correctly when looking up a property on each item', function () {
+      expectTemplate('{{#each items}}{{name}}{{/each}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ items: [{ name: 'Hello' }] })
+        .toCompileTo('Hello');
+    });
+
+    it('should still throw when a property is missing at all depths', function () {
+      expectTemplate('{{#each items}}{{name}}{{/each}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ items: [1, 2] })
+        .toThrow(Exception, /"name" not defined in/);
+    });
+
+    it('should still perform recursive lookup when a property is not in the current context', function () {
+      expectTemplate('{{#each items}}{{name}}{{/each}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ name: 'root', items: [{}] })
+        .toCompileTo('root');
+    });
+
+    it('should still perform recursive lookup with a multi-part path not in context', function () {
+      expectTemplate('{{#with child}}{{name.first}}{{/with}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ name: { first: 'root' }, child: { name: null } })
+        .toCompileTo('root');
+    });
+
+    it('should directly return an explicitly null property', function () {
+      expectTemplate('{{#each items}}{{name}}{{/each}}')
+        .withCompileOptions({ strict: true, compat: true })
+        .withInput({ name: 'root', items: [{ name: null }] })
+        .toCompileTo('');
+    });
+  });
+
   describe('assume objects', function () {
     it('should ignore missing property', function () {
       expectTemplate('{{hello}}')