[ES|QL] Remove variadic functions' optional args from the output of show functions

docs/reference/esql/functions/types/case.asciidoc

@@ -1,5 +1,5 @@
 [%header.monospaced.styled,format=dsv,separator=|]
 |===
-condition | rest | result
+condition | value | result
 
 |===

docs/reference/esql/functions/types/concat.asciidoc

@@ -1,6 +1,6 @@
 [%header.monospaced.styled,format=dsv,separator=|]
 |===
-first | rest | result
+string1 | string2 | result
 keyword | keyword | keyword
 text | text | keyword
 |===

x-pack/plugin/esql/qa/testFixtures/src/main/resources/show.csv-spec

@@ -17,11 +17,11 @@ atan                     |"double atan(n:double|integer|long|unsigned_long)"
 atan2                    |"double atan2(y:double|integer|long|unsigned_long, x:double|integer|long|unsigned_long)"                                       |[y, x]                   |["double|integer|long|unsigned_long", "double|integer|long|unsigned_long"]            |["y coordinate", "x coordinate"]                                            |double                    | "The angle between the positive x-axis and the ray from the origin to the point (x , y) in the Cartesian plane."                      | [false, false]       | false | false
 auto_bucket              |"double|date auto_bucket(field:integer|long|double|date, buckets:integer, from:integer|long|double|date|string, to:integer|long|double|date|string)"           |[field, buckets, from, to] |["integer|long|double|date", "integer", "integer|long|double|date|string", "integer|long|double|date|string"]      |["", "", "", ""]                                    | "double|date"                    | "Creates human-friendly buckets and returns a datetime value for each row that corresponds to the resulting bucket the row falls into."                      | [false, false, false, false]   | false | false
 avg                      |"double avg(field:double|integer|long)"                                           |field                     |"double|integer|long"                 |   ""                                               |double                    | "The average of a numeric field."                      | false                | false | true
-case                     |"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version case(condition:boolean, rest...:boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version)"                               |[condition, rest]             |["boolean", "boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version"]            |["", ""]                                            |"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version"                    | "Accepts pairs of conditions and values. The function returns the value that belongs to the first condition that evaluates to true."                      | [false, false]       | true | false
+case                     |"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version case(condition:boolean, value...:boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version)"                               |[condition, value]             |["boolean", "boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version"]            |["", ""]                                            |"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version"                    | "Accepts pairs of conditions and values. The function returns the value that belongs to the first condition that evaluates to true."                      | [false, false]       | true | false
 ceil                     |"double|integer|long|unsigned_long ceil(n:double|integer|long|unsigned_long)"     |n                        |"double|integer|long|unsigned_long"                 | ""                                                 | "double|integer|long|unsigned_long"                    | "Round a number up to the nearest integer."                      | false                | false | false
 cidr_match               |boolean cidr_match(ip:ip, blockX...:keyword)                         |[ip, blockX]             |[ip, keyword]            |["", "CIDR block to test the IP against."]                                            |boolean                    | "Returns true if the provided IP is contained in one of the provided CIDR blocks."                      | [false, false]       | true | false
-coalesce                 |"boolean|text|integer|keyword|long coalesce(expression:boolean|text|integer|keyword|long, expressionX...:boolean|text|integer|keyword|long)"                           |[expression, expressionX]             |["boolean|text|integer|keyword|long", "boolean|text|integer|keyword|long"]            |["Expression to evaluate", "Other expression to evaluate"]                                            |"boolean|text|integer|keyword|long"                    | "Returns the first of its arguments that is not null."                      | [false, false]       | true | false
-concat                   |"keyword concat(first:keyword|text, rest...:keyword|text)"                             |[first, rest]             |["keyword|text", "keyword|text"]            |["", ""]                                            |keyword                    | "Concatenates two or more strings."                      | [false, false]       | true | false
+coalesce                 |"boolean|text|integer|keyword|long coalesce(expression:boolean|text|integer|keyword|long, ?expressionX...:boolean|text|integer|keyword|long)"                           |expression             |"boolean|text|integer|keyword|long"            |"Expression to evaluate"                                            |"boolean|text|integer|keyword|long"                    | "Returns the first of its arguments that is not null."                      | false       | true | false
+concat                   |"keyword concat(string1:keyword|text, string2...:keyword|text)"                             |[string1, string2]             |["keyword|text", "keyword|text"]            |["", ""]                                            |keyword                    | "Concatenates two or more strings."                      | [false, false]       | true | false
 cos                      |"double cos(n:double|integer|long|unsigned_long)"      |n                        |"double|integer|long|unsigned_long"                 | "An angle, in radians"  |double         | "Returns the trigonometric cosine of an angle"                      | false                | false | false
 cosh                     |"double cosh(n:double|integer|long|unsigned_long)"     |n                        |"double|integer|long|unsigned_long"                 | "The number who's hyperbolic cosine is to be returned" |double                    | "Returns the hyperbolic cosine of a number"                      | false                | false | false
 count                    |"long count(?field:boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version)"                                         |field                     |"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version"                 | "Column or literal for which to count the number of values."                                                 |long                    | "Returns the total number (count) of input values."                      | true                | false | true
@@ -34,8 +34,8 @@ date_trunc               |"date date_trunc(interval:keyword, date:date)"
 e                        |double e()                                                   | null                    | null             | null                                               |double                    | "Euler’s number."                      | null                 | false | false
 ends_with                |"boolean ends_with(str:keyword|text, suffix:keyword|text)"                             |[str, suffix]             |["keyword|text", "keyword|text"]            |["", ""]                                            |boolean                    | "Returns a boolean that indicates whether a keyword string ends with another string"                      | [false, false]       | false | false
 floor                    |"double|integer|long|unsigned_long floor(n:double|integer|long|unsigned_long)"    |n                        |"double|integer|long|unsigned_long"    | ""                                                 |"double|integer|long|unsigned_long"                    | "Round a number down to the nearest integer."                      | false                | false | false
-greatest                 |"integer|long|double|boolean|keyword|text|ip|version greatest(first:integer|long|double|boolean|keyword|text|ip|version, rest...:integer|long|double|boolean|keyword|text|ip|version)"        |[first, rest]            |["integer|long|double|boolean|keyword|text|ip|version", "integer|long|double|boolean|keyword|text|ip|version"]            |["", ""]                                            |"integer|long|double|boolean|keyword|text|ip|version"                    | "Returns the maximum value from many columns."                      | [false, false]       | true | false
-least                    |"integer|long|double|boolean|keyword|text|ip|version least(first:integer|long|double|boolean|keyword|text|ip|version, rest...:integer|long|double|boolean|keyword|text|ip|version)"        |[first, rest]            |["integer|long|double|boolean|keyword|text|ip|version", "integer|long|double|boolean|keyword|text|ip|version"]            |["", ""]                                            |"integer|long|double|boolean|keyword|text|ip|version"                    | "Returns the minimum value from many columns."                      | [false, false]       | true | false
+greatest                 |"integer|long|double|boolean|keyword|text|ip|version greatest(first:integer|long|double|boolean|keyword|text|ip|version, ?rest...:integer|long|double|boolean|keyword|text|ip|version)"        |first           |"integer|long|double|boolean|keyword|text|ip|version"            |""                                            |"integer|long|double|boolean|keyword|text|ip|version"                    | "Returns the maximum value from many columns."                      | false       | true | false
+least                    |"integer|long|double|boolean|keyword|text|ip|version least(first:integer|long|double|boolean|keyword|text|ip|version, ?rest...:integer|long|double|boolean|keyword|text|ip|version)"        |first            |"integer|long|double|boolean|keyword|text|ip|version"            |""                                            |"integer|long|double|boolean|keyword|text|ip|version"                    | "Returns the minimum value from many columns."                      | false       | true | false
 left                     |"keyword left(str:keyword|text, length:integer)"                |[str, length]         |["keyword|text", "integer"]            |["", ""]                                            |keyword                    | "Return the substring that extracts length chars from the string starting from the left."                      | [false, false]       | false | false
 length                   |"integer length(str:keyword|text)"                                        |str                     |"keyword|text"                 | ""                                                 |integer                    | "Returns the character length of a string."                      | false                | false | false
 log                      |"double log(?base:integer|unsigned_long|long|double, value:integer|unsigned_long|long|double)"          |[base, value]                        |["integer|unsigned_long|long|double", "integer|unsigned_long|long|double"]| ["", ""]                                                 |double                    | "Returns the logarithm of a value to a base."                      | [true, false]                | false | false
@@ -119,11 +119,11 @@ synopsis:keyword
 "double atan2(y:double|integer|long|unsigned_long, x:double|integer|long|unsigned_long)"
 "double|date auto_bucket(field:integer|long|double|date, buckets:integer, from:integer|long|double|date|string, to:integer|long|double|date|string)"
 "double avg(field:double|integer|long)"
-"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version case(condition:boolean, rest...:boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version)"
+"boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version case(condition:boolean, value...:boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version)"
 "double|integer|long|unsigned_long ceil(n:double|integer|long|unsigned_long)"
 boolean cidr_match(ip:ip, blockX...:keyword) 
-"boolean|text|integer|keyword|long coalesce(expression:boolean|text|integer|keyword|long, expressionX...:boolean|text|integer|keyword|long)"
-"keyword concat(first:keyword|text, rest...:keyword|text)"
+"boolean|text|integer|keyword|long coalesce(expression:boolean|text|integer|keyword|long, ?expressionX...:boolean|text|integer|keyword|long)"
+"keyword concat(string1:keyword|text, string2...:keyword|text)"
 "double cos(n:double|integer|long|unsigned_long)"
 "double cosh(n:double|integer|long|unsigned_long)"
 "long count(?field:boolean|cartesian_point|date|double|geo_point|integer|ip|keyword|long|text|unsigned_long|version)"
@@ -136,8 +136,8 @@ keyword date_format(?format:keyword, date:date)
 double e()
 "boolean ends_with(str:keyword|text, suffix:keyword|text)"
 "double|integer|long|unsigned_long floor(n:double|integer|long|unsigned_long)"
-"integer|long|double|boolean|keyword|text|ip|version greatest(first:integer|long|double|boolean|keyword|text|ip|version, rest...:integer|long|double|boolean|keyword|text|ip|version)"
-"integer|long|double|boolean|keyword|text|ip|version least(first:integer|long|double|boolean|keyword|text|ip|version, rest...:integer|long|double|boolean|keyword|text|ip|version)"
+"integer|long|double|boolean|keyword|text|ip|version greatest(first:integer|long|double|boolean|keyword|text|ip|version, ?rest...:integer|long|double|boolean|keyword|text|ip|version)"
+"integer|long|double|boolean|keyword|text|ip|version least(first:integer|long|double|boolean|keyword|text|ip|version, ?rest...:integer|long|double|boolean|keyword|text|ip|version)"
 "keyword left(str:keyword|text, length:integer)"
 "integer length(str:keyword|text)"
 "double log(?base:integer|unsigned_long|long|double, value:integer|unsigned_long|long|double)"

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/conditional/Case.java

@@ -66,7 +66,7 @@ public Case(
         Source source,
         @Param(name = "condition", type = { "boolean" }) Expression first,
         @Param(
-            name = "rest",
+            name = "value",
             type = {
                 "boolean",
                 "cartesian_point",

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/conditional/Greatest.java

@@ -43,7 +43,8 @@ public class Greatest extends EsqlScalarFunction implements OptionalArgument {
     public Greatest(
         Source source,
         @Param(name = "first", type = { "integer", "long", "double", "boolean", "keyword", "text", "ip", "version" }) Expression first,
-        @Param(name = "rest", type = { "integer", "long", "double", "boolean", "keyword", "text", "ip", "version" }) List<Expression> rest
+        @Param(name = "rest", type = { "integer", "long", "double", "boolean", "keyword", "text", "ip", "version" }, optional = true) List<
+            Expression> rest
     ) {
         super(source, Stream.concat(Stream.of(first), rest.stream()).toList());
     }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/conditional/Least.java

@@ -43,7 +43,8 @@ public class Least extends EsqlScalarFunction implements OptionalArgument {
     public Least(
         Source source,
         @Param(name = "first", type = { "integer", "long", "double", "boolean", "keyword", "text", "ip", "version" }) Expression first,
-        @Param(name = "rest", type = { "integer", "long", "double", "boolean", "keyword", "text", "ip", "version" }) List<Expression> rest
+        @Param(name = "rest", type = { "integer", "long", "double", "boolean", "keyword", "text", "ip", "version" }, optional = true) List<
+            Expression> rest
     ) {
         super(source, Stream.concat(Stream.of(first), rest.stream()).toList());
     }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/nulls/Coalesce.java

@@ -55,7 +55,8 @@ public Coalesce(
         @Param(
             name = "expressionX",
             type = { "boolean", "text", "integer", "keyword", "long" },
-            description = "Other expression to evaluate"
+            description = "Other expression to evaluate",
+            optional = true
         ) List<Expression> rest
     ) {
         super(source, Stream.concat(Stream.of(first), rest.stream()).toList());

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/string/Concat.java

@@ -41,8 +41,8 @@ public class Concat extends EsqlScalarFunction {
     @FunctionInfo(returnType = "keyword", description = "Concatenates two or more strings.")
     public Concat(
         Source source,
-        @Param(name = "first", type = { "keyword", "text" }) Expression first,
-        @Param(name = "rest", type = { "keyword", "text" }) List<? extends Expression> rest
+        @Param(name = "string1", type = { "keyword", "text" }) Expression first,
+        @Param(name = "string2", type = { "keyword", "text" }) List<? extends Expression> rest
     ) {
         super(source, Stream.concat(Stream.of(first), rest.stream()).toList());
     }