From d55765a9b1b2bac905c71e7ec25da7465d2583c6 Mon Sep 17 00:00:00 2001
From: Teymour Aldridge <42674621+teymour-aldridge@users.noreply.github.com>
Date: Sun, 10 May 2020 16:26:45 +0100
Subject: [PATCH] Improve `html!` error messages. (#1192)

* Improve `html!` error messages.

* Improved some additional error messages.

* Improved error messages for iterables.

* Improved list error messages.

* Made a comment clearer.

* Updated an `html_tag` error message.

* Improved duplicate attribute error message.

* Updated tests to reflect updated error messages.

* Reformat code.

* Updated tests to reflect new error messages.

* Updated macro tests.

* Fix macro tests.

* Reformat code.
---
 yew-macro/src/html_tree/html_component.rs     |  8 ++---
 yew-macro/src/html_tree/html_iterable.rs      |  2 +-
 yew-macro/src/html_tree/html_list.rs          |  4 +--
 yew-macro/src/html_tree/html_tag/mod.rs       |  4 +--
 .../src/html_tree/html_tag/tag_attributes.rs  |  2 +-
 yew-macro/src/html_tree/mod.rs                |  4 +--
 .../tests/macro/html-component-fail.stderr    | 26 +++++++-------
 .../tests/macro/html-iterable-fail.stderr     |  2 +-
 yew-macro/tests/macro/html-list-fail.stderr   | 16 ++++-----
 yew-macro/tests/macro/html-node-fail.stderr   |  2 +-
 yew-macro/tests/macro/html-tag-fail.stderr    | 36 +++++++++----------
 11 files changed, 53 insertions(+), 53 deletions(-)

diff --git a/yew-macro/src/html_tree/html_component.rs b/yew-macro/src/html_tree/html_component.rs
index b0124c238dd..6efdd87d764 100644
--- a/yew-macro/src/html_tree/html_component.rs
+++ b/yew-macro/src/html_tree/html_component.rs
@@ -36,7 +36,7 @@ impl Parse for HtmlComponent {
             return match input.parse::<HtmlComponentClose>() {
                 Ok(close) => Err(syn::Error::new_spanned(
                     close,
-                    "this close tag has no corresponding open tag",
+                    "this closing tag has no corresponding opening tag",
                 )),
                 Err(err) => Err(err),
             };
@@ -57,7 +57,7 @@ impl Parse for HtmlComponent {
             if input.is_empty() {
                 return Err(syn::Error::new_spanned(
                     open,
-                    "this open tag has no corresponding close tag",
+                    "this opening tag has no corresponding closing tag",
                 ));
             }
             if let Some(ty) = HtmlComponentClose::peek(input.cursor()) {
@@ -376,7 +376,7 @@ impl Props {
     }
 
     fn collision_message() -> &'static str {
-        "Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop"
+        "Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop)."
     }
 }
 
@@ -467,7 +467,7 @@ impl Parse for Props {
                 p.node_ref = node_ref;
                 p.key = key;
 
-                // alphabetize
+                // sort alphabetically
                 p.props.sort_by(|a, b| {
                     if a.label == b.label {
                         Ordering::Equal
diff --git a/yew-macro/src/html_tree/html_iterable.rs b/yew-macro/src/html_tree/html_iterable.rs
index 712a018f55a..955a78016ac 100644
--- a/yew-macro/src/html_tree/html_iterable.rs
+++ b/yew-macro/src/html_tree/html_iterable.rs
@@ -26,7 +26,7 @@ impl Parse for HtmlIterable {
                 if err.to_string().starts_with("unexpected end of input") {
                     Err(syn::Error::new_spanned(
                         for_token,
-                        "expected expression after `for`",
+                        "expected an expression after the keyword `for`",
                     ))
                 } else {
                     Err(err)
diff --git a/yew-macro/src/html_tree/html_list.rs b/yew-macro/src/html_tree/html_list.rs
index 1f3e83622b1..5c08fbc5043 100644
--- a/yew-macro/src/html_tree/html_list.rs
+++ b/yew-macro/src/html_tree/html_list.rs
@@ -28,7 +28,7 @@ impl Parse for HtmlList {
             return match input.parse::<HtmlListClose>() {
                 Ok(close) => Err(syn::Error::new_spanned(
                     close,
-                    "this close tag has no corresponding open tag",
+                    "this closing tag has no corresponding opening tag",
                 )),
                 Err(err) => Err(err),
             };
@@ -38,7 +38,7 @@ impl Parse for HtmlList {
         if !HtmlList::verify_end(input.cursor()) {
             return Err(syn::Error::new_spanned(
                 open,
-                "this open tag has no corresponding close tag",
+                "this opening tag has no corresponding closing tag",
             ));
         }
 
diff --git a/yew-macro/src/html_tree/html_tag/mod.rs b/yew-macro/src/html_tree/html_tag/mod.rs
index 834d56ce542..91922bad01d 100644
--- a/yew-macro/src/html_tree/html_tag/mod.rs
+++ b/yew-macro/src/html_tree/html_tag/mod.rs
@@ -35,7 +35,7 @@ impl Parse for HtmlTag {
             return match input.parse::<HtmlTagClose>() {
                 Ok(close) => Err(syn::Error::new_spanned(
                     close,
-                    "this close tag has no corresponding open tag",
+                    "this closing tag has no corresponding opening tag",
                 )),
                 Err(err) => Err(err),
             };
@@ -56,7 +56,7 @@ impl Parse for HtmlTag {
             if input.is_empty() {
                 return Err(syn::Error::new_spanned(
                     open,
-                    "this open tag has no corresponding close tag",
+                    "this opening tag has no corresponding closing tag",
                 ));
             }
             if let Some(next_close_tag_name) = HtmlTagClose::peek(input.cursor()) {
diff --git a/yew-macro/src/html_tree/html_tag/tag_attributes.rs b/yew-macro/src/html_tree/html_tag/tag_attributes.rs
index 60ce0e61888..a4f3b1d6c1a 100644
--- a/yew-macro/src/html_tree/html_tag/tag_attributes.rs
+++ b/yew-macro/src/html_tree/html_tag/tag_attributes.rs
@@ -177,7 +177,7 @@ impl Parse for TagAttributes {
                 let label = &attributes[i + 1].label;
                 return Err(syn::Error::new_spanned(
                     label,
-                    format!("only one `{}` attribute allowed", label),
+                    format!("the attribute `{}` can only be specified once", label),
                 ));
             }
             i += 1;
diff --git a/yew-macro/src/html_tree/mod.rs b/yew-macro/src/html_tree/mod.rs
index afac21c8824..76c886bec79 100644
--- a/yew-macro/src/html_tree/mod.rs
+++ b/yew-macro/src/html_tree/mod.rs
@@ -55,7 +55,7 @@ impl Parse for HtmlRoot {
             let stream: TokenStream = input.parse()?;
             Err(syn::Error::new_spanned(
                 stream,
-                "only one root html element allowed",
+                "only one root html element is allowed (hint: you can wrap multiple html elements in a fragment `<></>`)",
             ))
         } else {
             Ok(html_root)
@@ -73,7 +73,7 @@ impl ToTokens for HtmlRoot {
 impl Parse for HtmlTree {
     fn parse(input: ParseStream) -> Result<Self> {
         let html_type = HtmlTree::peek(input.cursor())
-            .ok_or_else(|| input.error("expected valid html element"))?;
+            .ok_or_else(|| input.error("expected a valid html element"))?;
         let html_tree = match html_type {
             HtmlType::Empty => HtmlTree::Empty,
             HtmlType::Component => HtmlTree::Component(Box::new(input.parse()?)),
diff --git a/yew-macro/tests/macro/html-component-fail.stderr b/yew-macro/tests/macro/html-component-fail.stderr
index 12744668add..39dd21f9478 100644
--- a/yew-macro/tests/macro/html-component-fail.stderr
+++ b/yew-macro/tests/macro/html-component-fail.stderr
@@ -1,4 +1,4 @@
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
   --> $DIR/html-component-fail.rs:79:13
    |
 79 |     html! { <Child> };
@@ -30,7 +30,7 @@ error: unexpected token
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
   --> $DIR/html-component-fail.rs:83:13
    |
 83 |     html! { <Child with props > };
@@ -54,7 +54,7 @@ error: too many refs set
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop
+error: Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop).
   --> $DIR/html-component-fail.rs:86:38
    |
 86 |     html! { <Child with props ref=() value=1 ref=() /> };
@@ -62,7 +62,7 @@ error: Using special syntax `with props` along with named prop is not allowed. T
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop
+error: Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop).
   --> $DIR/html-component-fail.rs:87:31
    |
 87 |     html! { <Child with props value=1 ref=()  ref=() /> };
@@ -70,7 +70,7 @@ error: Using special syntax `with props` along with named prop is not allowed. T
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop
+error: Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop).
   --> $DIR/html-component-fail.rs:88:28
    |
 88 |     html! { <Child value=1 with props  ref=()  ref=() /> };
@@ -78,7 +78,7 @@ error: Using special syntax `with props` along with named prop is not allowed. T
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop
+error: Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop).
   --> $DIR/html-component-fail.rs:89:35
    |
 89 |     html! { <Child value=1 ref=() with props ref=() /> };
@@ -102,7 +102,7 @@ error: unexpected token
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop
+error: Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop).
   --> $DIR/html-component-fail.rs:93:28
    |
 93 |     html! { <Child value=1 with props /> };
@@ -110,7 +110,7 @@ error: Using special syntax `with props` along with named prop is not allowed. T
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: Using special syntax `with props` along with named prop is not allowed. This rule does not apply to special `ref` prop
+error: Using the `with props` syntax in combination with named props is not allowed (note: this does not apply to the `ref` prop).
   --> $DIR/html-component-fail.rs:94:31
    |
 94 |     html! { <Child with props value=1 /> };
@@ -150,7 +150,7 @@ error: too many refs set
     |
     = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
    --> $DIR/html-component-fail.rs:106:13
     |
 106 |     html! { </Child> };
@@ -158,7 +158,7 @@ error: this close tag has no corresponding open tag
     |
     = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
    --> $DIR/html-component-fail.rs:107:13
     |
 107 |     html! { <Child><Child></Child> };
@@ -166,7 +166,7 @@ error: this open tag has no corresponding close tag
     |
     = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one root html element allowed
+error: only one root html element is allowed (hint: you can wrap multiple html elements in a fragment `<></>`)
    --> $DIR/html-component-fail.rs:108:28
     |
 108 |     html! { <Child></Child><Child></Child> };
@@ -174,7 +174,7 @@ error: only one root html element allowed
     |
     = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
    --> $DIR/html-component-fail.rs:117:30
     |
 117 |     html! { <Generic<String>></Generic> };
@@ -182,7 +182,7 @@ error: this close tag has no corresponding open tag
     |
     = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
    --> $DIR/html-component-fail.rs:118:30
     |
 118 |     html! { <Generic<String>></Generic<Vec<String>>> };
diff --git a/yew-macro/tests/macro/html-iterable-fail.stderr b/yew-macro/tests/macro/html-iterable-fail.stderr
index ce71d45531c..9a91575233c 100644
--- a/yew-macro/tests/macro/html-iterable-fail.stderr
+++ b/yew-macro/tests/macro/html-iterable-fail.stderr
@@ -1,4 +1,4 @@
-error: expected expression after `for`
+error: expected an expression after the keyword `for`
  --> $DIR/html-iterable-fail.rs:4:13
   |
 4 |     html! { for };
diff --git a/yew-macro/tests/macro/html-list-fail.stderr b/yew-macro/tests/macro/html-list-fail.stderr
index a3fea8a6809..971f77bdbfe 100644
--- a/yew-macro/tests/macro/html-list-fail.stderr
+++ b/yew-macro/tests/macro/html-list-fail.stderr
@@ -1,4 +1,4 @@
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
  --> $DIR/html-list-fail.rs:4:13
   |
 4 |     html! { <> };
@@ -6,7 +6,7 @@ error: this open tag has no corresponding close tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
  --> $DIR/html-list-fail.rs:5:13
   |
 5 |     html! { </> };
@@ -14,7 +14,7 @@ error: this close tag has no corresponding open tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
  --> $DIR/html-list-fail.rs:6:13
   |
 6 |     html! { <><> };
@@ -22,7 +22,7 @@ error: this open tag has no corresponding close tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
  --> $DIR/html-list-fail.rs:7:13
   |
 7 |     html! { </></> };
@@ -30,7 +30,7 @@ error: this close tag has no corresponding open tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
  --> $DIR/html-list-fail.rs:8:13
   |
 8 |     html! { <><></> };
@@ -38,7 +38,7 @@ error: this open tag has no corresponding close tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one root html element allowed
+error: only one root html element is allowed (hint: you can wrap multiple html elements in a fragment `<></>`)
  --> $DIR/html-list-fail.rs:9:18
   |
 9 |     html! { <></><></> };
@@ -46,7 +46,7 @@ error: only one root html element allowed
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: expected valid html element
+error: expected a valid html element
   --> $DIR/html-list-fail.rs:10:15
    |
 10 |     html! { <>invalid</> };
@@ -62,7 +62,7 @@ error: unexpected end of input, expected expression
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
   --> $DIR/html-list-fail.rs:12:13
    |
 12 |     html! { <key="key".to_string()>invalid</key>}
diff --git a/yew-macro/tests/macro/html-node-fail.stderr b/yew-macro/tests/macro/html-node-fail.stderr
index 9446d747a0c..89ea5687a89 100644
--- a/yew-macro/tests/macro/html-node-fail.stderr
+++ b/yew-macro/tests/macro/html-node-fail.stderr
@@ -1,4 +1,4 @@
-error: only one root html element allowed
+error: only one root html element is allowed (hint: you can wrap multiple html elements in a fragment `<></>`)
  --> $DIR/html-node-fail.rs:4:21
   |
 4 |     html! { "valid" "invalid" };
diff --git a/yew-macro/tests/macro/html-tag-fail.stderr b/yew-macro/tests/macro/html-tag-fail.stderr
index d13496e52fd..37946af2056 100644
--- a/yew-macro/tests/macro/html-tag-fail.stderr
+++ b/yew-macro/tests/macro/html-tag-fail.stderr
@@ -1,4 +1,4 @@
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
  --> $DIR/html-tag-fail.rs:6:13
   |
 6 |     html! { <div> };
@@ -6,7 +6,7 @@ error: this open tag has no corresponding close tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
  --> $DIR/html-tag-fail.rs:7:18
   |
 7 |     html! { <div><div> };
@@ -14,7 +14,7 @@ error: this open tag has no corresponding close tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
  --> $DIR/html-tag-fail.rs:8:13
   |
 8 |     html! { </div> };
@@ -22,7 +22,7 @@ error: this close tag has no corresponding open tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this open tag has no corresponding close tag
+error: this opening tag has no corresponding closing tag
  --> $DIR/html-tag-fail.rs:9:13
   |
 9 |     html! { <div><div></div> };
@@ -30,7 +30,7 @@ error: this open tag has no corresponding close tag
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one root html element allowed
+error: only one root html element is allowed (hint: you can wrap multiple html elements in a fragment `<></>`)
   --> $DIR/html-tag-fail.rs:10:24
    |
 10 |     html! { <div></div><div></div> };
@@ -38,7 +38,7 @@ error: only one root html element allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
   --> $DIR/html-tag-fail.rs:11:18
    |
 11 |     html! { <div></span> };
@@ -46,7 +46,7 @@ error: this close tag has no corresponding open tag
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
   --> $DIR/html-tag-fail.rs:12:20
    |
 12 |     html! { <tag-a></tag-b> };
@@ -54,7 +54,7 @@ error: this close tag has no corresponding open tag
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: this close tag has no corresponding open tag
+error: this closing tag has no corresponding opening tag
   --> $DIR/html-tag-fail.rs:13:18
    |
 13 |     html! { <div></span></div> };
@@ -62,7 +62,7 @@ error: this close tag has no corresponding open tag
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one root html element allowed
+error: only one root html element is allowed (hint: you can wrap multiple html elements in a fragment `<></>`)
   --> $DIR/html-tag-fail.rs:14:20
    |
 14 |     html! { <img /></img> };
@@ -70,7 +70,7 @@ error: only one root html element allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: expected valid html element
+error: expected a valid html element
   --> $DIR/html-tag-fail.rs:15:18
    |
 15 |     html! { <div>Invalid</div> };
@@ -78,7 +78,7 @@ error: expected valid html element
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `attr` attribute allowed
+error: the attribute `attr` can only be specified once
   --> $DIR/html-tag-fail.rs:17:27
    |
 17 |     html! { <input attr=1 attr=2 /> };
@@ -86,7 +86,7 @@ error: only one `attr` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `value` attribute allowed
+error: the attribute `value` can only be specified once
   --> $DIR/html-tag-fail.rs:18:32
    |
 18 |     html! { <input value="123" value="456" /> };
@@ -94,7 +94,7 @@ error: only one `value` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `kind` attribute allowed
+error: the attribute `kind` can only be specified once
   --> $DIR/html-tag-fail.rs:19:36
    |
 19 |     html! { <input kind="checkbox" kind="submit" /> };
@@ -102,7 +102,7 @@ error: only one `kind` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `checked` attribute allowed
+error: the attribute `checked` can only be specified once
   --> $DIR/html-tag-fail.rs:20:33
    |
 20 |     html! { <input checked=true checked=false /> };
@@ -110,7 +110,7 @@ error: only one `checked` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `disabled` attribute allowed
+error: the attribute `disabled` can only be specified once
   --> $DIR/html-tag-fail.rs:21:34
    |
 21 |     html! { <input disabled=true disabled=false /> };
@@ -118,7 +118,7 @@ error: only one `disabled` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `selected` attribute allowed
+error: the attribute `selected` can only be specified once
   --> $DIR/html-tag-fail.rs:22:35
    |
 22 |     html! { <option selected=true selected=false /> };
@@ -126,7 +126,7 @@ error: only one `selected` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `class` attribute allowed
+error: the attribute `class` can only be specified once
   --> $DIR/html-tag-fail.rs:23:32
    |
 23 |     html! { <div class="first" class="second" /> };
@@ -134,7 +134,7 @@ error: only one `class` attribute allowed
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: only one `ref` attribute allowed
+error: the attribute `ref` can only be specified once
   --> $DIR/html-tag-fail.rs:38:27
    |
 38 |     html! { <input ref=() ref=() /> };