Introduce minify_query (#67)

Useful to reduce the size of payload

Author: kamilkisiela

src/lib.rs

@@ -105,5 +105,6 @@ pub mod schema;
 
 pub use crate::query::parse_query;
 pub use crate::schema::parse_schema;
+pub use crate::query::minify_query;
 pub use crate::position::Pos;
 pub use crate::format::Style;

src/query/minify.rs

@@ -0,0 +1,84 @@
+use crate::tokenizer::{Kind, Token, TokenStream};
+use combine::StreamOnce;
+use thiserror::Error;
+
+/// Error minifying query
+#[derive(Error, Debug)]
+#[error("query minify error: {}", _0)]
+pub struct MinifyError(String);
+
+pub fn minify_query<'a>(source: String) ->  Result<String, MinifyError> {
+  let mut bits: Vec<&str> = Vec::new();
+  let mut stream = TokenStream::new(source.as_str());
+  let mut prev_was_punctuator = false;
+
+  loop {
+      match stream.uncons() {
+          Ok(x) => {
+              let token: Token = x;
+              let is_non_punctuator = token.kind != Kind::Punctuator;
+
+              if prev_was_punctuator {
+                  if is_non_punctuator {
+                      bits.push(" ");
+                  }
+              }
+
+              bits.push(token.value);
+              prev_was_punctuator = is_non_punctuator;
+          }
+          Err(ref e) if e == &combine::easy::Error::end_of_input() => break,
+          Err(e) => return Err(MinifyError(e.to_string())),
+      }
+  }
+
+  Ok(bits.join(""))
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn strip_ignored_characters() {
+        let source = "
+        query SomeQuery($foo: String!, $bar: String) {
+            someField(foo: $foo, bar: $bar) {
+                a
+                b { 
+                    ... on B {
+                        c 
+                        d 
+                    } 
+                } 
+            } 
+        }
+        ";
+
+        let minified = super::minify_query(source.to_string()).expect("minification failed");
+
+        assert_eq!(
+            &minified,
+            "query SomeQuery($foo:String!$bar:String){someField(foo:$foo bar:$bar){a b{...on B{c d}}}}"
+        );
+    }
+    
+    #[test]
+    fn unexpected_token() {
+        let source = "
+        query foo {
+            bar;
+        }
+        ";
+
+        let minified = super::minify_query(source.to_string());
+
+        assert_eq!(
+            minified.is_err(),
+            true
+        );
+
+        assert_eq!(
+            minified.unwrap_err().to_string(),
+            "query minify error: Unexpected `unexpected character ';'`"
+        );
+    }
+}

src/query/mod.rs

@@ -4,8 +4,9 @@ mod ast;
 mod error;
 mod format;
 mod grammar;
-
+mod minify;
 
 pub use self::grammar::{parse_query, consume_definition};
 pub use self::error::ParseError;
 pub use self::ast::*;
+pub use self::minify::minify_query;