Add missing Cypher 25 updates (GQL extended identifiers + subqeury expression change) (#1313)

Author: JPryce-Aklundh

modules/ROOT/pages/appendix/gql-conformance/index.adoc

@@ -1,7 +1,7 @@
 :description: Overview of Cypher's conformance to GQL.
 = GQL conformance
 
-*Last updated*: 2 June 2025 +
+*Last updated*: 18 June 2025 +
 *Neo4j version*: 2025.06
 
 GQL is the new link:https://www.iso.org/home.html[ISO] International Standard query language for graph databases.

modules/ROOT/pages/appendix/gql-conformance/supported-mandatory.adoc

@@ -211,10 +211,8 @@ In Cypher, `trim()` removes any whitespace character.
 | 21.1
 | Names and variables
 | xref:syntax/index.adoc[]
-| Cypher supports GQL’s lexical elements, with the following caveats:
+| Cypher supports GQL’s lexical elements, with the following caveat:
 
-* GQL allows for extended parameter identifiers.
-For example: `RETURN $0hello` is allowed in GQL but not Cypher.
 * GQL allows identifiers that are not variables to be delimited with both backticks and quotes.
 Cypher only allows backticks.
 For example: `MATCH (n) RETURN n."a prop"` is allowed in GQL but not Cypher.

modules/ROOT/pages/deprecations-additions-removals-compatibility.adoc

@@ -59,10 +59,10 @@ label:removed[]
 RETURN 1 as my\u0085identifier
 ----
 a|
-The Unicode character \`\u0085` has been removed for unescaped identifiers and is now considered a whitespace character.
-To continue using it, escape the identifier by adding backticks around it.
+The Unicode character `\u0085` (`Next Line`) has been removed for unescaped identifiers and is now considered a whitespace character.
+To continue using it, escape the identifier by adding backticks (++``++) around it.
 This applies to all unescaped identifiers in Cypher, such as label expressions, properties, variable names, or parameters.
-In the given example, the quoted identifier would be \`my�identifier`.
+In the given example, the quoted identifier would be `my\u0085identifier`.
 
 a|
 label:functionality[]
@@ -72,23 +72,24 @@ label:removed[]
 RETURN 1 as my$Identifier
 ----
 a|
-The character with the Unicode representation \`\u0024` has been removed for unescaped identifiers. To continue using it, escape the identifier by adding backticks around the identifier.
-This applies to all unescaped identifiers in Cypher, such as label expressions, properties, variable names, or parameters. In the given example, the quoted identifier would be \`my$identifier`.
+The character with the Unicode representation `\u0024` (`$`) has been removed for unescaped identifiers.
+To continue using it, escape the identifier by adding backticks (++``++) around the identifier.
+This applies to all unescaped identifiers in Cypher, such as label expressions, properties, variable names, or parameters. In the given example, the quoted identifier would be `my\u0024identifier`.
 
 The following Unicode Characters are removed in identifiers:
-'\u0000', '\u0001', '\u0002', '\u0003', '\u0004', '\u0005', '\u0006', '\u0007',
-'\u0008', '\u000E', '\u000F', '\u0010', '\u0011', '\u0012', '\u0013', '\u0014',
-'\u0015', '\u0016', '\u0017', '\u0018', '\u0019', '\u001A', '\u001B', '\u007F',
-'\u0080', '\u0081', '\u0082', '\u0083', '\u0084', '\u0086', '\u0087', '\u0088',
-'\u0089', '\u008A', '\u008B', '\u008C', '\u008D', '\u008E', '\u008F', '\u0090',
-'\u0091', '\u0092', '\u0093', '\u0094', '\u0095', '\u0096', '\u0097', '\u0098',
-'\u0099', '\u009A', '\u009B', '\u009C', '\u009D', '\u009E', '\u009F', '\u0024',
-'\u00A2', '\u00A3', '\u00A4', '\u00A5', '\u00AD', '\u0600', '\u0601', '\u0602',
-'\u0603', '\u0604', '\u0605', '\u061C', '\u06DD', '\u070F', '\u08E2', '\u180E',
-'\u200B', '\u200C', '\u200D', '\u200E', '\u200F', '\u202A', '\u202B', '\u202C',
-'\u202D', '\u202E', '\u2060', '\u2061', '\u2062', '\u2063', '\u2064', '\u2066',
-'\u2067', '\u2068', '\u2069', '\u206A', '\u206B', '\u206C', '\u206D', '\u206E',
-'\u206F', '\u2E2F', '\uFEFF', '\uFFF9', '\uFFFA', '\uFFFB'
+`\u0000`, `\u0001`, `\u0002`, `\u0003`, `\u0004`, `\u0005`, `\u0006`, `\u0007`,
+`\u0008`, `\u000E`, `\u000F`, `\u0010`, `\u0011`, `\u0012`, `\u0013`, `\u0014`,
+`\u0015`, `\u0016`, `\u0017`, `\u0018`, `\u0019`, `\u001A`, `\u001B`, `\u007F`,
+`\u0080`, `\u0081`, `\u0082`, `\u0083`, `\u0084`, `\u0086`, `\u0087`, `\u0088`,
+`\u0089`, `\u008A`, `\u008B`, `\u008C`, `\u008D`, `\u008E`, `\u008F`, `\u0090`,
+`\u0091`, `\u0092`, `\u0093`, `\u0094`, `\u0095`, `\u0096`, `\u0097`, `\u0098`,
+`\u0099`, `\u009A`, `\u009B`, `\u009C`, `\u009D`, `\u009E`, `\u009F`, `\u0024`,
+`\u00A2`, `\u00A3`, `\u00A4`, `\u00A5`, `\u00AD`, `\u0600`, `\u0601`, `\u0602`,
+`\u0603`, `\u0604`, `\u0605`, `\u061C`, `\u06DD`, `\u070F`, `\u08E2`, `\u180E`,
+`\u200B`, `\u200C`, `\u200D`, `\u200E`, `\u200F`, `\u202A`, `\u202B`, `\u202C`,
+`\u202D`, `\u202E`, `\u2060`, `\u2061`, `\u2062`, `\u2063`, `\u2064`, `\u2066`,
+`\u2067`, `\u2068`, `\u2069`, `\u206A`, `\u206B`, `\u206C`, `\u206D`, `\u206E`,
+`\u206F`, `\u2E2F`, `\uFEFF`, `\uFFF9`, `\uFFFA`, `\uFFFB`
 
 a|
 label:functionality[]
@@ -186,6 +187,35 @@ For more information, see link:{neo4j-docs-base-uri}/operations-manual/current/d
 | Feature
 | Details
 
+a|
+label:functionality[]
+label:updated[]
+[source, cypher, role="noheader"]
+----
+WITH 1 AS g
+RETURN COLLECT {
+        UNWIND [1,2,3] AS x
+        WITH * WHERE x < 0
+        WITH count(*) AS agg
+        RETURN agg + g
+} AS x
+----
+
+a| Imported variables are now correctly handled as constants inside xref:subqueries/collect.adoc[`COLLECT`], xref:subqueries/count.adoc[`COUNT`], and xref:subqueries/existential.adoc[`EXISTS`] subquery expressions.
+The example query previously returned no results (`[]`) because the imported variable was used incorrectly as an implicit grouping key.
+It now returns `[1]`, since the variable is not used as a grouping key, allowing `count(*)` to return `0` and `0 + g` to evaluate to `1`.
+
+a|
+label:functionality[]
+label:updated[]
+[source, cypher, role="noheader"]
+----
+RETURN $0hello
+----
+
+a| Parameters can start with extended identifier characters (such as numbers), in line with the xref:appendix/gql-conformance/index.adoc[GQL] standard.
+For more information, see xref:syntax/parameters.adoc[].
+
 a|
 label:functionality[]
 label:updated[]

modules/ROOT/pages/syntax/parameters.adoc

@@ -26,7 +26,9 @@ Parameters cannot be used for the following constructs, as these form part of th
 * Relationship types; `MATCH (n)-[:$param]->(m)` is invalid.
 * Node labels; `MATCH (n:$param)` is invalid.
 
-Parameters may consist of letters and numbers, and any combination of these, but cannot start with a number or a currency symbol.
+Parameter names can start with and contain underscores, letters, numbers, and combining marks such as accents (e.g., `é`).
+Currency symbols (e.g., `$` and `€`), non-printable Unicode control characters that only affect formatting (e.g., `\t` for Tab), punctuation (e.g., `!`), and whitespaces are not allowed in any position of a parameter name.
+For example, `$héllo`, `$0param`, and `$_param` are valid, while `$€value`, `$hello!`, and `$bad param` are not.
 
 Setting parameters when running a query is dependent on the client environment.
 For example: