Rename field error to execution error; define response position (#1152)

* Rename 'field error' to 'runtime error' and define 'error position'

* Request errors should not be raised during CoerceArgumentValues

* Typo

* Rename 'runtime error' to 'execution error'

* Oops, missed out these edits

* Use definition in final paragraph

* lift up + other feedback

* lift response position to top section

---------

Co-authored-by: Lee Byron <[email protected]>

Author: benjie

Diff for: spec/Section 3 -- Type System.md

@@ -329,8 +329,8 @@ A GraphQL schema may describe that a field represents a list of another type;
 the `List` type is provided for this reason, and wraps another type.
 
 Similarly, the `Non-Null` type wraps another type, and denotes that the
-resulting value will never be {null} (and that a _field error_ cannot result in
-a {null} value).
+resulting value will never be {null} (and that an _execution error_ cannot
+result in a {null} value).
 
 These two types are referred to as "wrapping types"; non-wrapping types are
 referred to as "named types". A wrapping type has an underlying named type,
@@ -461,14 +461,14 @@ more guidance.
 
 A GraphQL service, when preparing a field of a given scalar type, must uphold
 the contract the scalar type describes, either by coercing the value or
-producing a _field error_ if a value cannot be coerced or if coercion may result
-in data loss.
+producing an _execution error_ if a value cannot be coerced or if coercion may
+result in data loss.
 
 A GraphQL service may decide to allow coercing different internal types to the
 expected return type. For example when coercing a field of type {Int} a boolean
 {true} value may produce {1} or a string value {"123"} may be parsed as base-10
 {123}. However if internal type coercion cannot be reasonably performed without
-losing information, then it must raise a _field error_.
+losing information, then it must raise an _execution error_.
 
 Since this coercion behavior is not observable to clients of the GraphQL
 service, the precise rules of coercion are left to the implementation. The only
@@ -513,15 +513,15 @@ Fields returning the type {Int} expect to encounter 32-bit integer internal
 values.
 
 GraphQL services may coerce non-integer internal values to integers when
-reasonable without losing information, otherwise they must raise a _field
+reasonable without losing information, otherwise they must raise an _execution
 error_. Examples of this may include returning `1` for the floating-point number
 `1.0`, or returning `123` for the string `"123"`. In scenarios where coercion
-may lose data, raising a field error is more appropriate. For example, a
-floating-point number `1.2` should raise a field error instead of being
+may lose data, raising an execution error is more appropriate. For example, a
+floating-point number `1.2` should raise an execution error instead of being
 truncated to `1`.
 
 If the integer internal value represents a value less than -2<sup>31</sup> or
-greater than or equal to 2<sup>31</sup>, a _field error_ should be raised.
+greater than or equal to 2<sup>31</sup>, an _execution error_ should be raised.
 
 **Input Coercion**
 
@@ -548,12 +548,12 @@ Fields returning the type {Float} expect to encounter double-precision
 floating-point internal values.
 
 GraphQL services may coerce non-floating-point internal values to {Float} when
-reasonable without losing information, otherwise they must raise a _field
+reasonable without losing information, otherwise they must raise an _execution
 error_. Examples of this may include returning `1.0` for the integer number `1`,
 or `123.0` for the string `"123"`.
 
 Non-finite floating-point internal values ({NaN} and {Infinity}) cannot be
-coerced to {Float} and must raise a _field error_.
+coerced to {Float} and must raise an _execution error_.
 
 **Input Coercion**
 
@@ -579,9 +579,9 @@ that representation must be used to serialize this type.
 Fields returning the type {String} expect to encounter Unicode string values.
 
 GraphQL services may coerce non-string raw values to {String} when reasonable
-without losing information, otherwise they must raise a _field error_. Examples
-of this may include returning the string `"true"` for a boolean true value, or
-the string `"1"` for the integer `1`.
+without losing information, otherwise they must raise an _execution error_.
+Examples of this may include returning the string `"true"` for a boolean true
+value, or the string `"1"` for the integer `1`.
 
 **Input Coercion**
 
@@ -600,8 +600,8 @@ representation of the integers `1` and `0`.
 Fields returning the type {Boolean} expect to encounter boolean internal values.
 
 GraphQL services may coerce non-boolean raw values to {Boolean} when reasonable
-without losing information, otherwise they must raise a _field error_. Examples
-of this may include returning `true` for non-zero numbers.
+without losing information, otherwise they must raise an _execution error_.
+Examples of this may include returning `true` for non-zero numbers.
 
 **Input Coercion**
 
@@ -623,7 +623,7 @@ large 128-bit random numbers, to base64 encoded values, or string values of a
 format like [GUID](https://en.wikipedia.org/wiki/Globally_unique_identifier).
 
 GraphQL services should coerce as appropriate given the ID formats they expect.
-When coercion is not possible they must raise a _field error_.
+When coercion is not possible they must raise an _execution error_.
 
 **Input Coercion**
 
@@ -1492,7 +1492,7 @@ enum Direction {
 **Result Coercion**
 
 GraphQL services must return one of the defined set of possible values. If a
-reasonable coercion is not possible they must raise a _field error_.
+reasonable coercion is not possible they must raise an _execution error_.
 
 **Input Coercion**
 
@@ -1654,10 +1654,10 @@ is constructed with the following rules:
 
 - If a variable is provided for an input object field, the runtime value of that
   variable must be used. If the runtime value is {null} and the field type is
-  non-null, a _field error_ must be raised. If no runtime value is provided, the
-  variable definition's default value should be used. If the variable definition
-  does not provide a default value, the input object field definition's default
-  value should be used.
+  non-null, an _execution error_ must be raised. If no runtime value is
+  provided, the variable definition's default value should be used. If the
+  variable definition does not provide a default value, the input object field
+  definition's default value should be used.
 
 Following are examples of input coercion for an input object type with a
 `String` field `a` and a required (non-null) `Int!` field `b`:
@@ -1742,19 +1742,19 @@ brackets like this: `pets: [Pet]`. Nesting lists is allowed: `matrix: [[Int]]`.
 
 GraphQL services must return an ordered list as the result of a list type. Each
 item in the list must be the result of a result coercion of the item type. If a
-reasonable coercion is not possible it must raise a _field error_. In
+reasonable coercion is not possible it must raise an _execution error_. In
 particular, if a non-list is returned, the coercion should fail, as this
 indicates a mismatch in expectations between the type system and the
 implementation.
 
 If a list's item type is nullable, then errors occurring during preparation or
 coercion of an individual item in the list must result in a the value {null} at
-that position in the list along with a _field error_ added to the response. If a
-list's item type is non-null, a field error occurring at an individual item in
-the list must result in a field error for the entire list.
+that position in the list along with an _execution error_ added to the response.
+If a list's item type is non-null, an execution error occurring at an individual
+item in the list must result in an execution error for the entire list.
 
-Note: See [Handling Field Errors](#sec-Handling-Field-Errors) for more about
-this behavior.
+Note: See [Handling Execution Errors](#sec-Handling-Execution-Errors) for more
+about this behavior.
 
 **Input Coercion**
 
@@ -1812,12 +1812,13 @@ always optional and non-null types are always required.
 In all of the above result coercions, {null} was considered a valid value. To
 coerce the result of a Non-Null type, the coercion of the wrapped type should be
 performed. If that result was not {null}, then the result of coercing the
-Non-Null type is that result. If that result was {null}, then a _field error_
-must be raised.
+Non-Null type is that result. If that result was {null}, then an _execution
+error_ must be raised.
 
-Note: When a _field error_ is raised on a non-null value, the error propagates
-to the parent field. For more information on this process, see
-[Errors and Non-Null Fields](#sec-Executing-Selection-Sets.Errors-and-Non-Null-Fields)
+Note: When an _execution error_ is raised on a non-null _response position_, the
+error propagates to the parent _response position_. For more information on this
+process, see
+[Errors and Non-Null Types](#sec-Executing-Selection-Sets.Errors-and-Non-Null-Types)
 within the Execution section.
 
 **Input Coercion**

Diff for: spec/Section 5 -- Validation.md

@@ -2010,4 +2010,4 @@ query booleanArgQueryWithDefault($booleanArg: Boolean = true) {
 ```
 
 Note: The value {null} could still be provided to such a variable at runtime. A
-non-null argument must raise a _field error_ if provided a {null} value.
+non-null argument must raise an _execution error_ if provided a {null} value.

Diff for: spec/Section 6 -- Execution.md

@@ -137,7 +137,7 @@ ExecuteQuery(query, schema, variableValues, initialValue):
 - Let {data} be the result of running {ExecuteSelectionSet(selectionSet,
   queryType, initialValue, variableValues)} _normally_ (allowing
   parallelization).
-- Let {errors} be the list of all _field error_ raised while executing the
+- Let {errors} be the list of all _execution error_ raised while executing the
   selection set.
 - Return an unordered map containing {data} and {errors}.
 
@@ -158,7 +158,7 @@ ExecuteMutation(mutation, schema, variableValues, initialValue):
 - Let {selectionSet} be the top level selection set in {mutation}.
 - Let {data} be the result of running {ExecuteSelectionSet(selectionSet,
   mutationType, initialValue, variableValues)} _serially_.
-- Let {errors} be the list of all _field error_ raised while executing the
+- Let {errors} be the list of all _execution error_ raised while executing the
   selection set.
 - Return an unordered map containing {data} and {errors}.
 
@@ -317,10 +317,10 @@ MapSourceToResponseEvent(sourceStream, subscription, schema, variableValues):
   - Complete {responseStream} normally.
 - Return {responseStream}.
 
-Note: Since {ExecuteSubscriptionEvent()} handles all _field error_, and _request
-error_ only occur during {CreateSourceEventStream()}, the only remaining error
-condition handled from {ExecuteSubscriptionEvent()} are internal exceptional
-errors not described by this specification.
+Note: Since {ExecuteSubscriptionEvent()} handles all _execution error_, and
+_request error_ only occur during {CreateSourceEventStream()}, the only
+remaining error condition handled from {ExecuteSubscriptionEvent()} are internal
+exceptional errors not described by this specification.
 
 ExecuteSubscriptionEvent(subscription, schema, variableValues, initialValue):
 
@@ -330,7 +330,7 @@ ExecuteSubscriptionEvent(subscription, schema, variableValues, initialValue):
 - Let {data} be the result of running {ExecuteSelectionSet(selectionSet,
   subscriptionType, initialValue, variableValues)} _normally_ (allowing
   parallelization).
-- Let {errors} be the list of all _field error_ raised while executing the
+- Let {errors} be the list of all _execution error_ raised while executing the
   selection set.
 - Return an unordered map containing {data} and {errors}.
 
@@ -376,17 +376,23 @@ ExecuteSelectionSet(selectionSet, objectType, objectValue, variableValues):
 Note: {resultMap} is ordered by which fields appear first in the operation. This
 is explained in greater detail in the Field Collection section below.
 
-**Errors and Non-Null Fields**
+**Errors and Non-Null Types**
 
-If during {ExecuteSelectionSet()} a field with a non-null {fieldType} raises a
-_field error_ then that error must propagate to this entire selection set,
-either resolving to {null} if allowed or further propagated to a parent field.
+<a name="sec-Executing-Selection-Sets.Errors-and-Non-Null-Fields">
+  <!-- Legacy link, this section was previously titled "Errors and Non-Null Fields" -->
+</a>
 
-If this occurs, any sibling fields which have not yet executed or have not yet
-yielded a value may be cancelled to avoid unnecessary work.
+If during {ExecuteSelectionSet()} a _response position_ with a non-null type
+raises an _execution error_ then that error must propagate to the parent
+response position (the entire selection set in the case of a field, or the
+entire list in the case of a list position), either resolving to {null} if
+allowed or being further propagated to a parent response position.
 
-Note: See [Handling Field Errors](#sec-Handling-Field-Errors) for more about
-this behavior.
+If this occurs, any sibling response positions which have not yet executed or
+have not yet yielded a value may be cancelled to avoid unnecessary work.
+
+Note: See [Handling Execution Errors](#sec-Handling-Execution-Errors) for more
+about this behavior.
 
 ### Normal and Serial Execution
 
@@ -646,7 +652,7 @@ CoerceArgumentValues(objectType, field, variableValues):
     - Add an entry to {coercedValues} named {argumentName} with the value
       {defaultValue}.
   - Otherwise if {argumentType} is a Non-Nullable type, and either {hasValue} is
-    not {true} or {value} is {null}, raise a _field error_.
+    not {true} or {value} is {null}, raise an _execution error_.
   - Otherwise if {hasValue} is {true}:
     - If {value} is {null}:
       - Add an entry to {coercedValues} named {argumentName} with the value
@@ -656,13 +662,16 @@ CoerceArgumentValues(objectType, field, variableValues):
         {value}.
     - Otherwise:
       - If {value} cannot be coerced according to the input coercion rules of
-        {argumentType}, raise a _field error_.
+        {argumentType}, raise an _execution error_.
       - Let {coercedValue} be the result of coercing {value} according to the
         input coercion rules of {argumentType}.
       - Add an entry to {coercedValues} named {argumentName} with the value
         {coercedValue}.
 - Return {coercedValues}.
 
+Any _request error_ raised as a result of input coercion during
+{CoerceArgumentValues()} should be treated instead as an _execution error_.
+
 Note: Variable values are not coerced because they are expected to be coerced
 before executing the operation in {CoerceVariableValues()}, and valid operations
 must only allow usage of variables of appropriate types.
@@ -703,12 +712,12 @@ CompleteValue(fieldType, fields, result, variableValues):
   - Let {innerType} be the inner type of {fieldType}.
   - Let {completedResult} be the result of calling {CompleteValue(innerType,
     fields, result, variableValues)}.
-  - If {completedResult} is {null}, raise a _field error_.
+  - If {completedResult} is {null}, raise an _execution error_.
   - Return {completedResult}.
 - If {result} is {null} (or another internal value similar to {null} such as
   {undefined}), return {null}.
 - If {fieldType} is a List type:
-  - If {result} is not a collection of values, raise a _field error_.
+  - If {result} is not a collection of values, raise an _execution error_.
   - Let {innerType} be the inner type of {fieldType}.
   - Return a list where each list item is the result of calling
     {CompleteValue(innerType, fields, resultItem, variableValues)}, where
@@ -743,7 +752,7 @@ CoerceResult(leafType, value):
 - Return the result of calling the internal method provided by the type system
   for determining the "result coercion" of {leafType} given the value {value}.
   This internal method must return a valid value for the type and not {null}.
-  Otherwise raise a _field error_.
+  Otherwise raise an _execution error_.
 
 Note: If a field resolver returns {null} then it is handled within
 {CompleteValue()} before {CoerceResult()} is called. Therefore both the input
@@ -798,39 +807,46 @@ MergeSelectionSets(fields):
   - Append all selections in {fieldSelectionSet} to {selectionSet}.
 - Return {selectionSet}.
 
-### Handling Field Errors
+### Handling Execution Errors
+
+<a name="sec-Handling-Field-Errors">
+  <!-- Legacy link, this section was previously titled "Handling Execution Errors" -->
+</a>
 
-A _field error_ is an error raised from a particular field during value
-resolution or coercion. While these errors should be reported in the response,
-they are "handled" by producing a partial response.
+An _execution error_ is an error raised during field execution, value resolution
+or coercion, at a specific _response position_. While these errors must be
+reported in the response, they are "handled" by producing partial {"data"} in
+the _response_.
 
 Note: This is distinct from a _request error_ which results in a response with
 no data.
 
-If a field error is raised while resolving a field, it is handled as though the
-field returned {null}, and the error must be added to the {"errors"} list in the
-response.
-
-If the result of resolving a field is {null} (either because the function to
-resolve the field returned {null} or because a field error was raised), and that
-field is of a `Non-Null` type, then a field error is raised. The error must be
-added to the {"errors"} list in the response.
-
-If the field returns {null} because of a field error which has already been
-added to the {"errors"} list in the response, the {"errors"} list must not be
-further affected. That is, only one error should be added to the errors list per
-field.
-
-Since `Non-Null` type fields cannot be {null}, field errors are propagated to be
-handled by the parent field. If the parent field may be {null} then it resolves
-to {null}, otherwise if it is a `Non-Null` type, the field error is further
-propagated to its parent field.
-
-If a `List` type wraps a `Non-Null` type, and one of the elements of that list
-resolves to {null}, then the entire list must resolve to {null}. If the `List`
-type is also wrapped in a `Non-Null`, the field error continues to propagate
-upwards.
-
-If all fields from the root of the request to the source of the field error
-return `Non-Null` types, then the {"data"} entry in the response should be
-{null}.
+If an execution error is raised while resolving a field (either directly or
+nested inside any lists), it is handled as though the _response position_ at
+which the error occurred resolved to {null}, and the error must be added to the
+{"errors"} list in the response.
+
+If the result of resolving a _response position_ is {null} (either due to the
+result of {ResolveFieldValue()} or because an execution error was raised), and
+that position is of a `Non-Null` type, then an execution error is raised at that
+position. The error must be added to the {"errors"} list in the response.
+
+If a _response position_ resolves to {null} because of an execution error which
+has already been added to the {"errors"} list in the response, the {"errors"}
+list must not be further affected. That is, only one error should be added to
+the errors list per _response position_.
+
+Since `Non-Null` response positions cannot be {null}, execution errors are
+propagated to be handled by the parent _response position_. If the parent
+response position may be {null} then it resolves to {null}, otherwise if it is a
+`Non-Null` type, the execution error is further propagated to its parent
+_response position_.
+
+If a `List` type wraps a `Non-Null` type, and one of the _response position_
+elements of that list resolves to {null}, then the entire list _response
+position_ must resolve to {null}. If the `List` type is also wrapped in a
+`Non-Null`, the execution error continues to propagate upwards.
+
+If every _response position_ from the root of the request to the source of the
+execution error has a `Non-Null` type, then the {"data"} entry in the response
+should be {null}.