fix: Updating parser such that objective names can be omitted (#31)

Cargo.toml

@@ -15,6 +15,7 @@ anyhow = "1.0"
 pest = "2.7"
 pest_derive = "2.7"
 serde = { version = "1", features = ["derive"], optional = true }
+tiny_id = "0.1.6"
 
 [features]
 default = []

resources/optional_labels.lp

@@ -0,0 +1,11 @@
+\ LP format example
+
+Minimize
+x + 10 y
+Subject To
+r01:  x + y  >= 1
+
+Binaries
+ x y z a
+End
+

src/lp_file_format.pest

@@ -2,7 +2,7 @@
 // https://www.ibm.com/docs/en/icos/22.1.1?topic=cplex-lp-file-format-algebraic-representation
 // https://www.fico.com/fico-xpress-optimization/docs/dms2020-03/solver/optimizer/HTML/chapter10_sec_section102.html
 // https://www.gurobi.com/documentation/current/refman/lp_format.html
-//
+// 
 
 // Common
 WHITESPACE   = _{ " " }

src/lp_parts.rs

@@ -1,6 +1,7 @@
 use std::str::FromStr;
 
 use pest::iterators::Pair;
+use tiny_id::ShortCodeGenerator;
 
 use crate::{
     common::RuleExt,
@@ -9,9 +10,14 @@ use crate::{
 };
 
 #[allow(clippy::unwrap_used)]
-fn compose_objective(pair: Pair<'_, Rule>) -> anyhow::Result<Objective> {
-    let mut parts = pair.into_inner();
-    let name = parts.next().unwrap().as_str().to_string();
+fn compose_objective(pair: Pair<'_, Rule>, gen: &mut ShortCodeGenerator<char>) -> anyhow::Result<Objective> {
+    let mut parts = pair.into_inner().peekable();
+    // Objective name can be omitted in LP files, so we need to handle that case
+    let name = if parts.peek().unwrap().as_rule() == Rule::OBJECTIVE_NAME {
+        parts.next().unwrap().as_str().to_string()
+    } else {
+        format!("obj_{}", gen.next_string())
+    };
     let coefficients: anyhow::Result<Vec<_>> = parts.map(|p| p.into_inner().try_into()).collect();
     Ok(Objective { name, coefficients: coefficients? })
 }
@@ -84,7 +90,7 @@ fn get_bound(pair: Pair<'_, Rule>) -> Option<(&str, VariableType)> {
 #[allow(clippy::wildcard_enum_match_arm)]
 /// # Errors
 /// Returns an error if the `compose` fails
-pub fn compose(pair: Pair<'_, Rule>, mut parsed: LPProblem) -> anyhow::Result<LPProblem> {
+pub fn compose(pair: Pair<'_, Rule>, mut parsed: LPProblem, gen: &mut ShortCodeGenerator<char>) -> anyhow::Result<LPProblem> {
     match pair.as_rule() {
         // Problem Name
         Rule::PROBLEM_NAME => return Ok(parsed.with_problem_name(pair.as_str())),
@@ -93,7 +99,8 @@ pub fn compose(pair: Pair<'_, Rule>, mut parsed: LPProblem) -> anyhow::Result<LP
         Rule::MAX_SENSE => return Ok(parsed.with_sense(Sense::Maximize)),
         // Problem Objectives
         Rule::OBJECTIVES => {
-            let objectives: anyhow::Result<Vec<Objective>> = pair.into_inner().map(|inner_pair| compose_objective(inner_pair)).collect();
+            let objectives: anyhow::Result<Vec<Objective>> =
+                pair.into_inner().map(|inner_pair| compose_objective(inner_pair, gen)).collect();
             parsed.add_objective(objectives?);
         }
         // Problem Constraints

src/parse.rs

@@ -6,6 +6,7 @@ use std::{
 
 use crate::{lp_parts::compose, model::lp_problem::LPProblem, LParser, Rule};
 use pest::Parser;
+use tiny_id::ShortCodeGenerator;
 
 /// # Errors
 /// Returns an error if the `read_to_string` or `open` fails
@@ -28,8 +29,9 @@ pub fn parse_lp_file(contents: &str) -> anyhow::Result<LPProblem> {
         anyhow::bail!("Invalid LP file");
     };
     let mut parsed_contents = LPProblem::default();
+    let mut code_generator = ShortCodeGenerator::new_lowercase_alphanumeric(6);
     for pair in pair.clone().into_inner() {
-        parsed_contents = compose(pair, parsed_contents)?;
+        parsed_contents = compose(pair, parsed_contents, &mut code_generator)?;
     }
     Ok(parsed_contents)
 }

tests/test_from_file.rs

@@ -52,6 +52,7 @@ generate_test!(test, "test.lp", Maximize, 1, 4, 12);
 generate_test!(test2, "test2.lp", Maximize, 1, 7, 139);
 generate_test!(empty_bounds, "empty_bounds.lp", Minimize, 1, 1, 2);
 generate_test!(blank_lines, "blank_lines.lp", Minimize, 1, 1, 3);
+generate_test!(optional_labels, "optional_labels.lp", Minimize, 1, 1, 4);
 
 #[test]
 #[ignore = "fit2d.mps takes > 60 seconds"]