core: Implement struct field access in declarative calls (spec v1.4.0)

This commit implements support for struct field access in declarative calls,
allowing subgraphs to access nested struct fields using dot notation.

Key changes:
- Add struct field access parsing and validation
- Support arbitrary nesting depth for field access
- Update subgraph manifest documentation
- Add comprehensive tests for struct field access functionality
- Update API version to support new feature

Author: fubhy

chain/ethereum/src/data_source.rs

@@ -41,7 +41,7 @@ use graph::{
 
 use graph::data::subgraph::{
     calls_host_fn, DataSourceContext, Source, MIN_SPEC_VERSION, SPEC_VERSION_0_0_8,
-    SPEC_VERSION_1_2_0,
+    SPEC_VERSION_1_2_0, SPEC_VERSION_1_4_0,
 };
 
 use crate::adapter::EthereumAdapter as _;
@@ -74,6 +74,38 @@ pub struct DataSource {
     pub contract_abi: Arc<MappingABI>,
 }
 
+/// Checks if a declarative call uses struct field access that would require spec version 1.4.0+
+/// This detects if the call was parsed with ABI context to resolve named fields
+fn call_uses_named_field_access(call_expr: &graph::data_source::common::CallExpr) -> bool {
+    // Check address for struct field access
+    if has_struct_field_access(&call_expr.address) {
+        return true;
+    }
+
+    // Check all arguments for struct field access
+    for arg in &call_expr.args {
+        if has_struct_field_access(arg) {
+            return true;
+        }
+    }
+
+    false
+}
+
+/// Helper function to check if a CallArg uses struct field access
+fn has_struct_field_access(arg: &graph::data_source::common::CallArg) -> bool {
+    use graph::data_source::common::{CallArg, EthereumArg};
+
+    match arg {
+        CallArg::Ethereum(EthereumArg::StructField(_, indices)) => {
+            // If we have struct field access with indices, it means named fields were resolved
+            // This feature requires spec version 1.4.0+
+            !indices.is_empty()
+        }
+        _ => false,
+    }
+}
+
 impl blockchain::DataSource<Chain> for DataSource {
     fn from_template_info(
         info: InstanceDSTemplateInfo,
@@ -380,6 +412,19 @@ impl blockchain::DataSource<Chain> for DataSource {
             }
         }
 
+        if spec_version < &SPEC_VERSION_1_4_0 {
+            for handler in &self.mapping.event_handlers {
+                for call in handler.calls.decls.as_ref() {
+                    if call_uses_named_field_access(&call.expr) {
+                        errors.push(anyhow!(
+                            "handler {}: struct field access by name in declarative calls is only supported for specVersion >= 1.4.0", handler.event
+                        ));
+                        break;
+                    }
+                }
+            }
+        }
+
         for handler in &self.mapping.event_handlers {
             for call in handler.calls.decls.as_ref() {
                 match self.mapping.find_abi(&call.expr.abi) {
@@ -800,7 +845,7 @@ impl DataSource {
                     "transaction" => format!("{}", &transaction.hash),
                 });
                 let handler = event_handler.handler.clone();
-                let calls = DeclaredCall::from_log_trigger(
+                let calls = DeclaredCall::from_log_trigger_with_event(
                     &self.mapping,
                     &event_handler.calls,
                     &log,

docs/subgraph-manifest.md

@@ -98,7 +98,7 @@ The `mapping` field may be one of the following supported mapping manifests:
 
 ### 1.5.3 Declaring calls
 
-_Available from spec version 1.2.0_
+_Available from spec version 1.2.0. Struct field access available from spec version 1.4.0_
 
 Declared calls are performed in parallel before the handler is run and can
 greatly speed up syncing. Mappings access the call results simply by using
@@ -118,7 +118,17 @@ Each call is of the form `<ABI>[<address>].<function>(<args>)`:
 | **function** | *String* | The name of a view function in the contract |
 | **args** | *[Expr]* | The arguments to pass to the function |
 
-The `Expr` can be either `event.address` or `event.params.<name>`.
+#### Expression Types
+
+The `Expr` can be one of the following:
+
+| Expression | Description |
+| --- | --- |
+| **event.address** | The address of the contract that emitted the event |
+| **event.params.&lt;name&gt;** | A simple parameter from the event |
+| **event.params.&lt;name&gt;.&lt;index&gt;** | A field from a struct parameter by numeric index |
+| **event.params.&lt;name&gt;.&lt;fieldName&gt;** | A field from a struct parameter by field name (spec version 1.4.0+) |
+
 
 ## 1.6 Path
 A path has one field `path`, which either refers to a path of a file on the local dev machine or an [IPLD link](https://github.com/ipld/specs/).

graph/src/data/subgraph/api_version.rs

@@ -60,8 +60,11 @@ pub const SPEC_VERSION_1_2_0: Version = Version::new(1, 2, 0);
 // represents the write order across all entity types in the subgraph.
 pub const SPEC_VERSION_1_3_0: Version = Version::new(1, 3, 0);
 
+// Enables struct field access in declarative calls
+pub const SPEC_VERSION_1_4_0: Version = Version::new(1, 4, 0);
+
 // The latest spec version available
-pub const LATEST_VERSION: &Version = &SPEC_VERSION_1_3_0;
+pub const LATEST_VERSION: &Version = &SPEC_VERSION_1_4_0;
 
 pub const MIN_SPEC_VERSION: Version = Version::new(0, 0, 2);