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

Adds named field access support for struct parameters in declarative calls
(e.g., event.params.asset.addr). Field names are resolved to indices at
parse time using ABI context for improved performance and user experience.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

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) {
@@ -805,7 +850,6 @@ impl DataSource {
                     &event_handler.calls,
                     &log,
                     &params,
-                    Some(&event_handler.event),
                 )?;
                 Ok(Some(TriggerWithHandler::<Chain>::new_with_logging_extras(
                     MappingTrigger::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
@@ -122,76 +122,12 @@ Each call is of the form `<ABI>[<address>].<function>(<args>)`:
 
 The `Expr` can be one of the following:
 
-| Expression | Description | Example |
-| --- | --- | --- |
-| **event.address** | The address of the contract that emitted the event | `event.address` |
-| **event.params.&lt;name&gt;** | A simple parameter from the event | `event.params.token` |
-| **event.params.&lt;name&gt;.&lt;index&gt;** | A field from a struct parameter by numeric index | `event.params.asset.0` |
-| **event.params.&lt;name&gt;.&lt;fieldName&gt;** | A field from a struct parameter by field name | `event.params.asset.addr` |
-| **Nested struct access** | Arbitrary nesting depth with mixed access patterns | `event.params.data.1.user.id` |
-
-#### Struct Field Access
-
-When event parameters contain struct types (tuples in ABI), you can access individual fields using either numeric indices or field names:
-
-**Numeric Access (Traditional):**
-```yaml
-calls:
-  tokenAddress: ERC20[event.params.asset.0].name()  # First field
-  tokenAmount: ERC20[event.params.asset.1].decimals()  # Second field
-```
-
-**Named Access (Recommended):**
-```yaml
-calls:
-  tokenAddress: ERC20[event.params.asset.addr].name()     # By field name
-  tokenAmount: ERC20[event.params.asset.amount].decimals() # By field name
-```
-
-**Mixed Access Patterns:**
-```yaml
-calls:
-  # Access first transfer, then recipient field by name
-  recipient: Token[event.params.transfers.0.recipient].balanceOf()
-  
-  # Deep nesting with mixed numeric and named access
-  innerValue: Contract[event.params.data.1.user.addr].someFunction()
-```
-
-#### Struct Field Access Examples
-
-Given an event with this ABI structure:
-```json
-{
-  "name": "AssetTransfer",
-  "type": "event", 
-  "inputs": [
-    {
-      "name": "asset",
-      "type": "tuple",
-      "components": [
-        {"name": "addr", "type": "address"},
-        {"name": "amount", "type": "uint256"},
-        {"name": "active", "type": "bool"}
-      ]
-    }
-  ]
-}
-```
-
-You can access fields in multiple ways:
-```yaml
-calls:
-  # Named field access (clearest and recommended)
-  tokenContract: ERC20[event.params.asset.addr].name()
-  tokenDecimals: ERC20[event.params.asset.addr].decimals()
-  
-  # Numeric field access (backward compatible)  
-  tokenContract: ERC20[event.params.asset.0].name()
-  
-  # Mixed access for complex nested structures
-  nestedField: Contract[event.params.data.0.inner.fieldName].process()
-```
+| 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

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);