From 1a1ee75e0ee3edbdbdb0c22f494486c996ced6de Mon Sep 17 00:00:00 2001
From: Christoph Hegemann <christoph.hegemann@sourcegraph.com>
Date: Mon, 1 Jul 2024 06:25:54 +0200
Subject: [PATCH] adds a simple error type to allow producing nicer errors

---
 .../crates/scip-syntax/src/scip_strict.rs     |  1 +
 .../src/scip_strict/context_error.rs          | 49 ++++++++++++++++++
 .../scip-syntax/src/scip_strict/parse.rs      | 50 ++++++++++---------
 3 files changed, 77 insertions(+), 23 deletions(-)
 create mode 100644 docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/context_error.rs

diff --git a/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict.rs b/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict.rs
index 4e349028a751..63f27da4a672 100644
--- a/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict.rs
+++ b/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict.rs
@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 
+mod context_error;
 mod format;
 mod parse;
 
diff --git a/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/context_error.rs b/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/context_error.rs
new file mode 100644
index 000000000000..f7f45f3e5ddc
--- /dev/null
+++ b/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/context_error.rs
@@ -0,0 +1,49 @@
+use std::fmt;
+
+use nom::error::{ContextError, ErrorKind, FromExternalError, ParseError};
+
+/// default error type, only contains the error's location and code
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct CtxError<I> {
+    /// position of the error in the input data
+    pub input: I,
+    /// contextual error message
+    pub context: &'static str,
+}
+
+impl<I> ParseError<I> for CtxError<I> {
+    fn from_error_kind(input: I, _kind: ErrorKind) -> Self {
+        CtxError {
+            input,
+            context: "no context set yet",
+        }
+    }
+
+    fn append(_: I, _: ErrorKind, other: Self) -> Self {
+        other
+    }
+}
+
+impl<I> ContextError<I> for CtxError<I> {
+    fn add_context(_input: I, context: &'static str, mut other: Self) -> Self {
+        other.context = context;
+        other
+    }
+}
+
+impl<I, E> FromExternalError<I, E> for CtxError<I> {
+    /// Create a new error from an input position and an external error
+    fn from_external_error(input: I, _kind: ErrorKind, _e: E) -> Self {
+        CtxError {
+            input,
+            context: "no context set yet",
+        }
+    }
+}
+
+/// The Display implementation allows the std::error::Error implementation
+impl<I: fmt::Display> fmt::Display for CtxError<I> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "error '{}' at: {}", self.context, self.input)
+    }
+}
diff --git a/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/parse.rs b/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/parse.rs
index 51fe9eee822b..c7f16403eabc 100644
--- a/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/parse.rs
+++ b/docker-images/syntax-highlighter/crates/scip-syntax/src/scip_strict/parse.rs
@@ -1,29 +1,26 @@
-use std::borrow::Cow;
+use std::{borrow::Cow, str};
 
 use nom::{
     branch::alt,
     bytes::complete::{tag, take_while1},
     character::complete::char,
-    combinator::{cut, eof, fail, opt},
-    error::{context, convert_error, VerboseError},
+    combinator::{cut, eof, fail, opt, verify},
+    error::context,
     multi::many1,
     sequence::{delimited, preceded, tuple},
     Finish, IResult, Parser,
 };
 
-use super::{Descriptor, NonLocalSymbol, Package, Scheme, Symbol};
+use super::{context_error::CtxError, Descriptor, NonLocalSymbol, Package, Scheme, Symbol};
 
 pub(super) fn parse_symbol(input: &str) -> Result<Symbol<'_>, String> {
     match parse_symbol_inner(input).finish() {
         Ok((_, symbol)) => Ok(symbol),
-        Err(err) => Err(format!(
-            "Invalid symbol: '{input}'\n{}",
-            convert_error(input, err)
-        )),
+        Err(err) => Err(format!("Invalid symbol: '{input}'\n{err}",)),
     }
 }
 
-type PResult<'a, A> = IResult<&'a str, A, VerboseError<&'a str>>;
+type PResult<'a, A> = IResult<&'a str, A, CtxError<&'a str>>;
 
 fn parse_symbol_inner(input: &str) -> PResult<'_, Symbol<'_>> {
     let (input, symbol) = alt((parse_local_symbol, parse_nonlocal_symbol))(input)?;
@@ -38,26 +35,33 @@ fn parse_local_symbol(input: &str) -> PResult<'_, Symbol<'_>> {
 }
 
 fn parse_nonlocal_symbol(input: &str) -> PResult<'_, Symbol<'_>> {
-    tuple((
-        parse_space_terminated,
-        parse_package,
-        many1(parse_descriptor),
-    ))
-    .map(|(scheme, package, descriptors)| {
-        Symbol::NonLocal(NonLocalSymbol {
-            scheme: Scheme(scheme),
-            package,
-            descriptors,
+    tuple((parse_scheme, parse_package, many1(parse_descriptor)))
+        .map(|(scheme, package, descriptors)| {
+            Symbol::NonLocal(NonLocalSymbol {
+                scheme,
+                package,
+                descriptors,
+            })
         })
-    })
+        .parse(input)
+}
+
+fn parse_scheme(input: &str) -> PResult<'_, Scheme> {
+    context(
+        "Invalid scheme",
+        verify(parse_space_terminated, |s: &Cow<'_, str>| {
+            !s.starts_with("local")
+        }),
+    )
+    .map(Scheme)
     .parse(input)
 }
 
 fn parse_package(input: &str) -> PResult<'_, Package> {
     tuple((
-        parse_space_terminated,
-        parse_space_terminated,
-        parse_space_terminated,
+        context("Invalid package manager", parse_space_terminated),
+        context("Invalid package name", parse_space_terminated),
+        context("Invalid package version", parse_space_terminated),
     ))
     .map(|(manager, package_name, version)| Package {
         manager,