From 7e04eb51ff34f7947f396ef30b8e53edc1dc3f2c Mon Sep 17 00:00:00 2001
From: Andrew Twyman <artwyman@users.noreply.github.com>
Date: Thu, 11 Sep 2025 12:23:46 -0700
Subject: [PATCH] Optional dot syntax for anchored keys (#423)

---
 book/src/anchoredkeys.md  |  9 ++++++---
 book/src/simpleexample.md |  2 +-
 src/examples/mod.rs       |  8 ++++----
 src/lang/grammar.pest     |  7 +++++--
 src/lang/parser.rs        | 11 ++++++++---
 src/lang/processor.rs     | 17 ++++++++++++-----
 6 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/book/src/anchoredkeys.md b/book/src/anchoredkeys.md
index d2fd38d..33d0142 100644
--- a/book/src/anchoredkeys.md
+++ b/book/src/anchoredkeys.md
@@ -12,10 +12,13 @@ some of its arguments is proved, it means that a valid Merkle proof of the
 value behind it exists and was used at some point to construct a `Contains`
 statement that introduced that anchored key.
 
+In PODLang, anchored key indexing can use subscript syntax `foo["bar"]` which
+allows any string key, or dot syntax `foo.bar` if the key is a valid identifier.
+
 For example:
 ```
 0: None
-1: Contains(foo, bar, 42) <- ContainsFromEntries 0 0 0 mt_proof
-2: Lt(foo[bar], 100) <- LtFromEntries 1 0
-3: NotEqual(foo[bar], 100) <- LtToNotEqual 2
+1: Contains(foo, "bar", 42) <- ContainsFromEntries 0 0 0 mt_proof
+2: Lt(foo["bar"], 100) <- LtFromEntries 1 0
+3: NotEqual(foo.bar, 100) <- LtToNotEqual 2
 ```
diff --git a/book/src/simpleexample.md b/book/src/simpleexample.md
index 840823d..d6a127a 100644
--- a/book/src/simpleexample.md
+++ b/book/src/simpleexample.md
@@ -59,7 +59,7 @@ Equals(a, c)
 First, we need to decompose all the anchored keys as (dict, key) pairs.  This is the frontend description of the deduction rule.
 ```
 IF
-Equals(a_or[a_key], b_or[b_key)
+Equals(a_or[a_key], b_or[b_key])
 AND
 Equals(b_or[b_key], c_or[c_key])
 THEN
diff --git a/src/examples/mod.rs b/src/examples/mod.rs
index 8ab2d55..868f783 100644
--- a/src/examples/mod.rs
+++ b/src/examples/mod.rs
@@ -82,10 +82,10 @@ pub fn zu_kyc_pod_request(gov_signer: &Value, pay_signer: &Value) -> Result<PodR
     let input = format!(
         r#"
     REQUEST(
-        SetNotContains({sanction_set}, ?gov["idNumber"])
-        Lt(?gov["dateOfBirth"], {ZU_KYC_NOW_MINUS_18Y})
-        Equal(?pay["startDate"], {ZU_KYC_NOW_MINUS_1Y})
-        Equal(?gov["socialSecurityNumber"], ?pay["socialSecurityNumber"])
+        SetNotContains({sanction_set}, ?gov.idNumber)
+        Lt(?gov.dateOfBirth, {ZU_KYC_NOW_MINUS_18Y})
+        Equal(?pay.startDate, {ZU_KYC_NOW_MINUS_1Y})
+        Equal(?gov.socialSecurityNumber, ?pay.socialSecurityNumber)
         SignedBy(?gov, {gov_signer})
         SignedBy(?pay, {pay_signer})
         // TODO: Ownership check and watermarking
diff --git a/src/lang/grammar.pest b/src/lang/grammar.pest
index adbd276..252c8ed 100644
--- a/src/lang/grammar.pest
+++ b/src/lang/grammar.pest
@@ -54,8 +54,11 @@ statement_arg_list = { statement_arg ~ ("," ~ statement_arg)* }
 
 statement = { identifier ~ "(" ~ statement_arg_list? ~ ")" }
 
-// Anchored Key: ?Var["key_literal"]
-anchored_key = { wildcard ~ "[" ~ literal_string ~ "]" }
+// Anchored Key: ?Var["key_literal"] or ?Var.key_identifier
+anchored_key = {
+    (wildcard ~ "[" ~ literal_string ~ "]")
+    | (wildcard ~ "." ~ identifier)
+}
 
 // Literal Values (ordered to avoid ambiguity, e.g., string before int)
 literal_value = {
diff --git a/src/lang/parser.rs b/src/lang/parser.rs
index b16d658..12bd22e 100644
--- a/src/lang/parser.rs
+++ b/src/lang/parser.rs
@@ -89,11 +89,16 @@ mod tests {
 
     #[test]
     fn test_parse_anchored_key() {
-        assert_parses(Rule::anchored_key, "?PodVar[\"literal_key\"]");
+        assert_parses(Rule::anchored_key, "?PodVar[\"literal key\"]");
+        assert_parses(Rule::anchored_key, "?PodVar.literal_key");
         assert_fails(Rule::anchored_key, "PodVar[\"key\"]"); // Needs wildcard for pod
-        assert_fails(Rule::anchored_key, "?PodVar[invalid_key]"); // Key must be literal string or wildcard
+        assert_fails(Rule::anchored_key, "PodVar.key"); // Needs wildcard for pod
+        assert_fails(Rule::anchored_key, "?PodVar[invalid_key]"); // Key must be literal string
+        assert_fails(Rule::anchored_key, "?PodVar.123"); // Key must be valid identifier
         assert_fails(Rule::anchored_key, "?PodVar[]"); // Key cannot be empty
+        assert_fails(Rule::anchored_key, "?PodVar."); // Key cannot be empty
         assert_fails(Rule::anchored_key, "?PodVar[?key]"); // Key cannot be wildcard
+        assert_fails(Rule::anchored_key, "?PodVar.?key"); // Key cannot be wildcard
     }
 
     #[test]
@@ -214,7 +219,7 @@ mod tests {
                 ValueOf(?ConstVal["min_age"], 18)
                 Gt(?UserPod["age"], ?ConstVal["min_age"])
                 // User must not be banned
-                NotContains(?_BANNED_USERS["list"], ?UserPod["userId"])
+                NotContains(?_BANNED_USERS.list, ?UserPod.userId)
             )
 
             REQUEST(
diff --git a/src/lang/processor.rs b/src/lang/processor.rs
index 32b296e..607c65e 100644
--- a/src/lang/processor.rs
+++ b/src/lang/processor.rs
@@ -356,7 +356,14 @@ fn pest_pair_to_builder_arg(
             }
 
             let key_part_pair = inner_ak_pairs.next().unwrap();
-            let key_str = parse_pest_string_literal(&key_part_pair)?;
+            let key_str = match key_part_pair.as_rule() {
+                Rule::literal_string => parse_pest_string_literal(&key_part_pair)?,
+                Rule::identifier => key_part_pair.as_str().to_string(),
+                _ => unreachable!(
+                    "unknown key type in anchored key: {:?}",
+                    key_part_pair.as_rule()
+                ),
+            };
             Ok(BuilderArg::Key(root_wc_str.to_string(), key_str))
         }
         _ => unreachable!("Unexpected rule: {:?}", arg_content_pair.as_rule()),
@@ -1065,7 +1072,7 @@ mod processor_tests {
 
     #[test]
     fn test_fp_only_request() -> Result<(), ProcessorError> {
-        let input = "REQUEST( Equal(?A[\"k\"],?B[\"k\"]) )"; // Escaped quotes
+        let input = "REQUEST( Equal(?A[\"k\"],?B.k) )"; // Escaped quotes
         let pairs = get_document_content_pairs(input)?;
         let params = Params::default();
         let mut ctx = ProcessingContext::new(&params);
@@ -1082,7 +1089,7 @@ mod processor_tests {
 
     #[test]
     fn test_fp_simple_predicate() -> Result<(), ProcessorError> {
-        let input = "my_pred(A, B) = AND( Equal(?A[\"k\"],?B[\"k\"]) )"; // Escaped quotes
+        let input = "my_pred(A, B) = AND( Equal(?A[\"k\"],?B.k) )"; // Escaped quotes
         let pairs = get_document_content_pairs(input)?;
         let params = Params::default();
         let mut ctx = ProcessingContext::new(&params);
@@ -1104,7 +1111,7 @@ mod processor_tests {
     #[test]
     fn test_fp_multiple_predicates() -> Result<(), ProcessorError> {
         let input = r#"
-            pred1(X) = AND( Equal(?X["k"],?X["k"]) )
+            pred1(X) = AND( Equal(?X["k"],?X.k) )
             pred2(Y, Z) = OR( Equal(?Y["v"], 123) )
         "#;
         let pairs = get_document_content_pairs(input)?;
@@ -1253,7 +1260,7 @@ mod processor_tests {
         // Native predicate names are case-sensitive
         let input = r#"
         REQUEST(
-          EQUAL(?A["b"], ?C["d"])
+          EQUAL(?A["b"], ?C.d)
         )
     "#;
         let pairs = get_document_content_pairs(input)?;