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

@@ -62,8 +62,8 @@ fn main() {
     let parser = Parser::new(input);
     let ast = parser.parse();
 
-    // ast.errors() returns an errors slice encountered during lexing and parsing
-    assert!(ast.errors().is_empty());
+    // ast.errors() returns an iterator with the errors encountered during lexing and parsing
+    assert_eq!(0, ast.errors().len());
 
     // ast.document() get the Document, or root node, of the tree that you can
     // start iterating on.
@@ -97,7 +97,7 @@ 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();
 
@@ -130,7 +130,7 @@ 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();
 

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();