feat: impl Iterator for errors

fixes #139

ast.errors() now return an `impl ExactSizeIterator` which allows us to iterate, but also check for the `len()`. It should allow us to use `is_empty()` as well eventually, if / when rust-lang/rust#35428 lands.

Author: o0Ignition0o

crates/apollo-parser/README.md

@@ -18,26 +18,31 @@
 </div>
 
 ## Features
-* Typed GraphQL AST as per [October 2021 specification]
-* Error resilience
-  * lexing and parsing does not fail or `panic` if a lexical or a syntax error is found
-* GraphQL lexer
-* GraphQL parser 
+
+- Typed GraphQL AST as per [October 2021 specification]
+- Error resilience
+  - lexing and parsing does not fail or `panic` if a lexical or a syntax error is found
+- GraphQL lexer
+- GraphQL parser
 
 ## Getting started
+
 Add this to your `Cargo.toml` to start using `apollo-parser`:
+
 ```toml
 # Just an example, change to the necessary package version.
 [dependencies]
 apollo_parser = "0.1.0"
 ```
 
 Or using [cargo-edit]:
+
 ```bash
 cargo add apollo_parser
 ```
 
 ## Usage
+
 `apollo-parser` is built to parse both GraphQL schemas and queries according to the latest [October 2021 specification]. It produces
 a typed syntax tree that then can we walked extracting all the necessary
 information. You can quick start with:
@@ -63,7 +68,7 @@ fn main() {
     let ast = parser.parse();
 
     // ast.errors() returns an errors slice encountered during lexing and parsing
-    assert!(ast.errors().is_empty());
+    assert_eq!(0, ast.errors().len());
 
     // ast.document() get the Document, or root node, of the tree that you can
     // start iterating on.
@@ -73,15 +78,17 @@ fn main() {
 
 ### Examples
 
-Two examples outlined here: 
-* [Get field names in an object]
-* [Get variables used in a query]
+Two examples outlined here:
+
+- [Get field names in an object]
+- [Get variables used in a query]
 
 The [examples directory] in this repository has a few more useful
 implementations such as:
-* [using apollo-rs with miette to display error diagnostics]
-* [using apollo-rs with annotate_snippets to display error diagnostics]
-* [checking for unused variables]
+
+- [using apollo-rs with miette to display error diagnostics]
+- [using apollo-rs with annotate_snippets to display error diagnostics]
+- [checking for unused variables]
 
 #### Get field names in an object
 
@@ -97,10 +104,10 @@ fn main() {
     ";
     let parser = Parser::new(input);
     let ast = parser.parse();
-    assert!(ast.errors().is_empty());
-  
+    assert_eq!(0, ast.errors().len());
+
     let doc = ast.document();
-  
+
     for def in doc.definitions() {
         if let ast::Definition::ObjectTypeDefinition(object_type) = def {
             assert_eq!(object_type.name().unwrap().text(), "ProductDimension");
@@ -112,7 +119,7 @@ fn main() {
 }
 ```
 
-#### Get variables used in a query 
+#### Get variables used in a query
 
 ```rust
 use apollo_parser::{ast, Parser};
@@ -127,17 +134,17 @@ fn main() {
       }
     }
     ";
-    
+
     let parser = Parser::new(input);
     let ast = parser.parse();
-    assert!(&ast.errors().is_empty());
-    
+    assert_eq!(0, &ast.errors().len());
+
     let doc = ast.document();
-    
+
     for def in doc.definitions() {
         if let ast::Definition::OperationDefinition(op_def) = def {
             assert_eq!(op_def.name().unwrap().text(), "GraphQuery");
-    
+
             let variable_defs = op_def.variable_definitions();
             let variables: Vec<String> = variable_defs
                 .iter()
@@ -155,6 +162,7 @@ fn main() {
 ```
 
 ## License
+
 Licensed under either of
 
 - Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
@@ -163,16 +171,17 @@ Licensed under either of
 at your option.
 
 #### Contribution
+
 Unless you explicitly state otherwise, any contribution intentionally submitted
 for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
 dual licensed as above, without any additional terms or conditions.
 
 [cargo-edit]: https://github.com/killercup/cargo-edit
-[apollo-rs: spec-compliant GraphQL Tools in Rust]: https://www.apollographql.com/blog/announcement/tooling/apollo-rs-graphql-tools-in-rust/
+[apollo-rs: spec-compliant graphql tools in rust]: https://www.apollographql.com/blog/announcement/tooling/apollo-rs-graphql-tools-in-rust/
 [examples directory]: https://github.com/apollographql/apollo-rs/tree/main/crates/apollo-parser/examples
-[Get field names in an object]: https://github.com/apollographql/apollo-rs#get-field-names-in-an-object
-[Get variables used in a query]: https://github.com/apollographql/apollo-rs#get-variables-used-in-a-query
+[get field names in an object]: https://github.com/apollographql/apollo-rs#get-field-names-in-an-object
+[get variables used in a query]: https://github.com/apollographql/apollo-rs#get-variables-used-in-a-query
 [using apollo-rs with miette to display error diagnostics]: https://github.com/apollographql/apollo-rs/blob/a7f616454a53dcb8496725ceac6c63eacddefb2c/crates/apollo-parser/examples/miette.rs
 [using apollo-rs with annotate_snippets to display error diagnostics]: https://github.com/apollographql/apollo-rs/blob/a7f616454a53dcb8496725ceac6c63eacddefb2c/crates/apollo-parser/examples/annotate_snippet.rs
 [checking for unused variables]: https://github.com/apollographql/apollo-rs/blob/a7f616454a53dcb8496725ceac6c63eacddefb2c/crates/apollo-parser/examples/unused_vars.rs
-[October 2021 specification]: https://spec.graphql.org/October2021
+[october 2021 specification]: https://spec.graphql.org/October2021

crates/apollo-parser/examples/unused_vars.rs

@@ -11,7 +11,7 @@ fn are_variables_unused() {
     let parser = Parser::new(&src);
     let ast = parser.parse();
 
-    assert!(&ast.errors().is_empty());
+    assert_eq!(0, ast.errors().len());
 
     let doc = ast.document();
 

crates/apollo-parser/src/ast/mod.rs

@@ -42,7 +42,7 @@
 //! let parser = Parser::new(schema);
 //! let ast = parser.parse();
 //!
-//! assert!(ast.errors().is_empty());
+//! assert_eq!(0, ast.errors().len());
 //! let document = ast.document();
 //! for definition in document.definitions() {
 //!     match definition {

crates/apollo-parser/src/error.rs

@@ -16,7 +16,7 @@ use std::fmt;
 /// let parser = Parser::new(input);
 /// let ast = parser.parse();
 ///
-/// assert!(ast.errors().is_empty());
+/// assert_eq!(0, ast.errors().len());
 ///
 /// let doc = ast.document();
 /// ```

crates/apollo-parser/src/lexer/mod.rs

@@ -59,8 +59,8 @@ impl Lexer {
     }
 
     /// Get a reference to the lexer's tokens.
-    pub(crate) fn errors(&self) -> &[Error] {
-        self.errors.as_slice()
+    pub(crate) fn errors<'e>(&'e self) -> impl ExactSizeIterator<Item = &'e Error> {
+        self.errors.iter()
     }
 }
 

crates/apollo-parser/src/lib.rs

@@ -62,7 +62,7 @@
 //! let ast = parser.parse();
 //!
 //! // ast.errors() returns an errors slice encountered during lexing and parsing
-//! assert!(ast.errors().is_empty());
+//! assert_eq!(0, ast.errors().len());
 //!
 //! // ast.document() get the Document, or root node, of the tree that you can
 //! // start iterating on.
@@ -94,7 +94,7 @@
 //! ";
 //! let parser = Parser::new(input);
 //! let ast = parser.parse();
-//! assert!(ast.errors().is_empty());
+//! assert_eq!(0, ast.errors().len());
 //!
 //! let doc = ast.document();
 //!
@@ -125,7 +125,7 @@
 //!
 //! let parser = Parser::new(input);
 //! let ast = parser.parse();
-//! assert!(&ast.errors().is_empty());
+//! assert_eq!(0, ast.errors().len());
 //!
 //! let doc = ast.document();
 //!

crates/apollo-parser/src/parser/grammar/object.rs

@@ -131,7 +131,7 @@ type Business implements NamedEntity & ValuedEntity & CatEntity {
 }";
         let parser = Parser::new(input);
         let ast = parser.parse();
-        assert!(ast.errors().is_empty());
+        assert_eq!(0, ast.errors().len());
 
         let doc = ast.document();
 

crates/apollo-parser/src/parser/grammar/selection.rs

@@ -68,7 +68,7 @@ mod test {
 ";
         let parser = Parser::new(input);
         let ast = parser.parse();
-        assert!(&ast.errors().is_empty());
+        assert_eq!(0, ast.errors().len());
 
         let doc = ast.document();
 
@@ -129,7 +129,7 @@ query GraphQuery($graph_id: ID!, $variant: String) {
 ";
         let parser = Parser::new(input);
         let ast = parser.parse();
-        assert!(&ast.errors().is_empty());
+        assert_eq!(0, ast.errors().len());
 
         let doc = ast.document();
 

crates/apollo-parser/src/parser/grammar/union_.rs

@@ -112,7 +112,7 @@ mod test {
         let input = "union SearchResult = Photo | Person | Cat | Dog";
         let parser = Parser::new(input);
         let ast = parser.parse();
-        assert!(ast.errors().is_empty());
+        assert_eq!(0, ast.errors().len());
 
         let doc = ast.document();
 

crates/apollo-parser/src/parser/grammar/value.rs

@@ -270,7 +270,7 @@ query GraphQuery($graph_id: ID!, $variant: String) {
         ";
         let parser = Parser::new(input);
         let ast = parser.parse();
-        assert!(&ast.errors().is_empty());
+        assert_eq!(0, ast.errors().len());
 
         let doc = ast.document();
 

crates/apollo-parser/src/parser/mod.rs

@@ -42,7 +42,7 @@ pub(crate) use token_text::TokenText;
 /// // Parse the query, and return a SyntaxTree.
 /// let ast = parser.parse();
 /// // Check that are no errors. These are not part of the AST.
-/// assert!(&ast.errors().is_empty());
+/// assert_eq!(0, ast.errors().len());
 ///
 /// // Get the document root node
 /// let doc = ast.document();
@@ -65,7 +65,7 @@ pub(crate) use token_text::TokenText;
 /// let parser = Parser::new(core_schema);
 /// let ast = parser.parse();
 ///
-/// assert!(ast.errors().is_empty());
+/// assert_eq!(0, ast.errors().len());
 ///
 /// let document = ast.document();
 /// ```
@@ -91,7 +91,7 @@ impl Parser {
             tokens.push(s);
         }
 
-        for e in lexer.errors().to_owned() {
+        for e in lexer.errors().cloned() {
             errors.push(e);
         }
 

crates/apollo-parser/src/parser/syntax_tree.rs

@@ -44,8 +44,8 @@ pub struct SyntaxTree {
 
 impl SyntaxTree {
     /// Get a reference to the syntax tree's errors.
-    pub fn errors(&self) -> &[crate::Error] {
-        self.errors.as_ref()
+    pub fn errors(&self) -> impl ExactSizeIterator<Item = &crate::Error> {
+        self.errors.iter()
     }
 
     /// Return the root typed `Document` node.
@@ -159,7 +159,7 @@ mod test {
         ";
         let parser = Parser::new(input);
         let ast = parser.parse();
-        assert!(ast.errors().is_empty());
+        assert_eq!(0, ast.errors().len());
 
         let doc = ast.document();
 

crates/apollo-parser/src/tests.rs

@@ -52,25 +52,24 @@ fn parser_tests() {
     });
 }
 
-fn assert_errors_are_present(errors: &[Error], path: &Path) {
+fn assert_errors_are_present<'e>(errors: impl ExactSizeIterator<Item = &'e Error>, path: &Path) {
     assert!(
-        !errors.is_empty(),
+        errors.len() != 0,
         "There should be errors in the file {:?}",
         path.display()
     );
 }
 
-fn assert_errors_are_absent(errors: &[Error], path: &Path) {
-    assert_eq!(
-        errors,
-        &[] as &[Error],
+fn assert_errors_are_absent<'e>(errors: impl ExactSizeIterator<Item = &'e Error>, path: &Path) {
+    assert!(
+        errors.len() == 0,
         "There should be no errors in the file {:?}",
         path.display(),
     );
 }
 
 /// Concatenate tokens and erorrs.
-fn dump_tokens_and_errors(tokens: &[Token], errors: &[Error]) -> String {
+fn dump_tokens_and_errors<'e>(tokens: &[Token], errors: impl Iterator<Item = &'e Error>) -> String {
     let mut acc = String::new();
     for token in tokens {
         writeln!(acc, "{:?}", token).unwrap();