Detailed Explanation of nvim_parse_expression Return Values

not allowed (determines whether they will stop parsing process or be recognized as an operator/space, though also yielding an error). • "l" when needing to start parsing with lvalues for ":let" or ":for". Common flag sets: • "m" to parse like for `":echo"`. • "E" to parse like for `"<C-r>="`. • empty string for ":call". • "lm" to parse for ":let". • {highlight} If true, return value will also include "highlight" key containing array of 4-tuples (arrays) (Integer, Integer, Integer, String), where first three numbers define the highlighted region and represent line, starting column and ending column (latter exclusive: one should highlight region [start_col, end_col)). Return: ~ • AST: top-level dict with these keys: • "error": Dict with error, present only if parser saw some error. Contains the following keys: • "message": String, error message in printf format, translated. Must contain exactly one "%.*s". • "arg": String, error message argument. • "len": Amount of bytes successfully parsed. With flags equal to "" that should be equal to the length of expr string. ("Successfully parsed" here means "participated in AST creation", not "till the first error".) • "ast": AST, either nil or a dict with these keys: • "type": node type, one of the value names from ExprASTNodeType stringified without "kExprNode" prefix. • "start": a pair `[line, column]` describing where node is "started" where "line" is always 0 (will not be 0 if you will be using this API on e.g. ":let", but that is not present yet). Both elements are Integers. • "len": “length” of the node. This and "start" are there for debugging purposes primary (debugging parser and providing debug information). • "children": a list of nodes described in top/"ast". There always is zero, one or two children, key will not be present if node has no children. Maximum number of children may be found in node_maxchildren array. • Local values (present only for certain nodes): • "scope": a single Integer, specifies scope for "Option" and "PlainIdentifier" nodes. For "Option" it is one of ExprOptScope values, for "PlainIdentifier" it is one of ExprVarScope values. • "ident": identifier (without scope, if any), present for "Option", "PlainIdentifier", "PlainKey" and "Environment" nodes. • "name": Integer, register name (one character) or -1. Only present for "Register" nodes. • "cmp_type": String, comparison type, one of the value names from ExprComparisonType, stringified without "kExprCmp" prefix. Only present for "Comparison" nodes. • "ccs_strategy": String, case comparison strategy, one of the value names from ExprCaseCompareStrategy, stringified without "kCCStrategy" prefix. Only present for "Comparison" nodes. • "augmentation": String, augmentation type for "Assignment" nodes. Is either an empty string, "Add", "Subtract" or "Concat" for "=", "+=", "-=" or ".=" respectively. • "invert": Boolean, true if result of comparison needs to be inverted. Only present for "Comparison" nodes. • "ivalue": Integer, integer value for "Integer" nodes. • "fvalue": Float, floating-point value for "Float" nodes. • "svalue": String, value for "SingleQuotedString" and "DoubleQuotedString"

This section provides a detailed explanation of the return values of the `nvim_parse_expression` function. It describes the structure of the returned dictionary, including the 'error', 'len', and 'ast' keys. The 'ast' key contains the abstract syntax tree, with information on node types, start position, length, and children. It also details local values that may be present for certain nodes, such as scope, identifier, register name, comparison type, case comparison strategy, augmentation type, and various value types (integer, float, string).