azure-policy parser: allow overriding the column-width limit (microsoft#673)

Some Azure Policy JSON documents contain very long lines — ARM template
expressions with deeply nested if()/concat() calls can easily exceed
the default 1024-column lexer limit.

Add Parser::new_with_max_col() and corresponding parse_policy_rule_with_max_col()
/ parse_policy_definition_with_max_col() entry points so callers can raise
the limit when needed.  Also bump ExprParser's own default to 65536 since
template expressions are routinely thousands of characters wide.

Author: anakrish

src/languages/azure_policy/expr.rs

@@ -70,6 +70,13 @@ impl<'source> ExprParser<'source> {
     fn new(source: &'source Source) -> Self {
         let mut lexer = Lexer::new(source);
         lexer.set_unknown_char_is_symbol(true);
+        // ARM template expressions inside Azure Policy JSON values can be
+        // very long (e.g. deeply nested `if(...)` / `concat(...)` spanning
+        // thousands of characters on a single line).  Use a generous column
+        // limit so these expressions parse successfully.
+        if let Some(limit) = core::num::NonZeroU32::new(65536) {
+            lexer.set_max_col(limit);
+        }
         let tok = Token(
             TokenKind::Eof,
             Span {

src/languages/azure_policy/parser/core.rs

@@ -148,8 +148,21 @@ pub(super) struct Parser<'source> {
 impl<'source> Parser<'source> {
     /// Create a new parser for the given source.
     pub fn new(source: &'source Source) -> Result<Self, ParseError> {
+        Self::new_with_max_col(source, None)
+    }
+
+    /// Create a new parser with an optional column-width override.
+    ///
+    /// When `max_col` is `None`, the lexer's default limit applies.
+    pub fn new_with_max_col(
+        source: &'source Source,
+        max_col: Option<core::num::NonZeroU32>,
+    ) -> Result<Self, ParseError> {
         let mut lexer = Lexer::new(source);
         lexer.set_unknown_char_is_symbol(true);
+        if let Some(mc) = max_col {
+            lexer.set_max_col(mc);
+        }
 
         let tok = lexer
             .next_token()

src/languages/azure_policy/parser/mod.rs

@@ -34,6 +34,8 @@ pub use error::ParseError;
 
 use alloc::string::ToString as _;
 
+use ::core::num::NonZeroU32;
+
 use crate::lexer::{Source, TokenKind};
 
 use super::ast::{Constraint, FieldKind, OperatorKind, PolicyDefinition, PolicyRule};
@@ -57,7 +59,15 @@ use self::core::Parser;
 ///
 /// Returns a span-annotated [`PolicyRule`] AST.
 pub fn parse_policy_rule(source: &Source) -> Result<PolicyRule, ParseError> {
-    let mut parser = Parser::new(source)?;
+    parse_policy_rule_with_max_col(source, None)
+}
+
+/// Like [`parse_policy_rule`] but with an optional column-width override.
+pub fn parse_policy_rule_with_max_col(
+    source: &Source,
+    max_col: Option<NonZeroU32>,
+) -> Result<PolicyRule, ParseError> {
+    let mut parser = Parser::new_with_max_col(source, max_col)?;
     let rule = parser.parse_policy_rule()?;
 
     if parser.tok.0 != TokenKind::Eof {
@@ -79,7 +89,15 @@ pub fn parse_policy_rule(source: &Source) -> Result<PolicyRule, ParseError> {
 /// Returns a [`PolicyDefinition`] with typed fields for known properties
 /// and a catch-all list of `extra` entries for everything else.
 pub fn parse_policy_definition(source: &Source) -> Result<PolicyDefinition, ParseError> {
-    let mut parser = Parser::new(source)?;
+    parse_policy_definition_with_max_col(source, None)
+}
+
+/// Like [`parse_policy_definition`] but with an optional column-width override.
+pub fn parse_policy_definition_with_max_col(
+    source: &Source,
+    max_col: Option<NonZeroU32>,
+) -> Result<PolicyDefinition, ParseError> {
+    let mut parser = Parser::new_with_max_col(source, max_col)?;
     let defn = parser.parse_policy_definition()?;
 
     if parser.tok.0 != TokenKind::Eof {