span_display utility

Summary: Extract from `Diagnostic` to use in the following diff D48941531.

Reviewed By: IanChilds

Differential Revision: D48940978

fbshipit-source-id: f708b4a2993119cfc57e14489bd59b946fd63cb0

Author: stepancheg

starlark_syntax/src/codemap.rs

@@ -468,6 +468,11 @@ impl<'a> FileSpanRef<'a> {
     pub fn resolve_span(&self) -> ResolvedSpan {
         self.file.resolve_span(self.span)
     }
+
+    /// Resolve the span.
+    pub fn source_span(self) -> &'a str {
+        self.file.source_span(self.span)
+    }
 }
 
 impl FileSpan {
@@ -485,7 +490,7 @@ impl FileSpan {
 
     /// Resolve the span.
     pub fn source_span(&self) -> &str {
-        self.file.source_span(self.span)
+        self.as_ref().source_span()
     }
 
     /// Cheap reference to the span.

starlark_syntax/src/diagnostic.rs

@@ -20,19 +20,11 @@ use std::fmt;
 use std::fmt::Display;
 use std::fmt::Formatter;
 
-use annotate_snippets::display_list::DisplayList;
-use annotate_snippets::display_list::FormatOptions;
-use annotate_snippets::snippet::Annotation;
-use annotate_snippets::snippet::AnnotationType;
-use annotate_snippets::snippet::Slice;
-use annotate_snippets::snippet::Snippet;
-use annotate_snippets::snippet::SourceAnnotation;
-
 use crate::call_stack::CallStack;
 use crate::codemap::CodeMap;
 use crate::codemap::FileSpan;
 use crate::codemap::Span;
-use crate::fast_string;
+use crate::span_display::span_display;
 
 /// An error plus its origination location and call stack.
 ///
@@ -126,54 +118,12 @@ impl Diagnostic {
     }
 
     /// Gets annotated snippets for a [`Diagnostic`].
-    fn get_display_list<'a>(&'a self, annotation_label: &'a str, color: bool) -> DisplayList<'a> {
-        fn convert_span_to_slice<'a>(span: &'a FileSpan) -> Slice<'a> {
-            let region = span.resolve_span();
-
-            // we want the source_span to capture any whitespace ahead of the diagnostic span to
-            // get the column numbers correct in the DisplayList, and any trailing source code
-            // on the last line for context.
-            let first_line_span = span.file.line_span(region.begin.line);
-            let last_line_span = span.file.line_span(region.end.line);
-            let source_span = span.span.merge(first_line_span).merge(last_line_span);
-            let source = span.file.source_span(source_span);
-
-            // We want to highlight the span, which needs to be relative to source, and in
-            // characters.
-            // Our spans are in terms of bytes, but our resolved spans in terms of characters.
-            let range_start_chars = region.begin.column;
-            let range_len_chars = fast_string::len(span.source_span()).0;
-
-            Slice {
-                source,
-                line_start: 1 + region.begin.line,
-                origin: Some(span.file.filename()),
-                fold: false,
-                annotations: vec![SourceAnnotation {
-                    label: "",
-                    annotation_type: AnnotationType::Error,
-                    range: (range_start_chars, range_start_chars + range_len_chars),
-                }],
-            }
-        }
-
-        let slice = self.span.as_ref().map(convert_span_to_slice);
-
-        let snippet = Snippet {
-            title: Some(Annotation {
-                label: Some(annotation_label),
-                id: None,
-                annotation_type: AnnotationType::Error,
-            }),
-            footer: Vec::new(),
-            slices: slice.map(|s| vec![s]).unwrap_or_default(),
-            opt: FormatOptions {
-                color,
-                ..Default::default()
-            },
-        };
-
-        DisplayList::from(snippet)
+    fn get_display_list<'a>(&'a self, annotation_label: &'a str, color: bool) -> impl Display + 'a {
+        span_display(
+            self.span.as_ref().map(|s| s.as_ref()),
+            annotation_label,
+            color,
+        )
     }
 }
 

starlark_syntax/src/lib.rs

@@ -38,4 +38,5 @@ pub mod lexer;
 #[cfg(test)]
 mod lexer_tests;
 pub mod slice_vec_ext;
+pub(crate) mod span_display;
 pub mod syntax;

starlark_syntax/src/span_display.rs

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2019 The Starlark in Rust Authors.
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use std::fmt::Display;
+
+use annotate_snippets::display_list::DisplayList;
+use annotate_snippets::display_list::FormatOptions;
+use annotate_snippets::snippet::Annotation;
+use annotate_snippets::snippet::AnnotationType;
+use annotate_snippets::snippet::Slice;
+use annotate_snippets::snippet::Snippet;
+use annotate_snippets::snippet::SourceAnnotation;
+
+use crate::codemap::FileSpanRef;
+use crate::fast_string;
+
+/// Gets annotated snippets for a [`Diagnostic`].
+pub(crate) fn span_display<'a>(
+    span: Option<FileSpanRef<'a>>,
+    annotation_label: &'a str,
+    color: bool,
+) -> impl Display + 'a {
+    fn convert_span_to_slice<'a>(span: FileSpanRef<'a>) -> Slice<'a> {
+        let region = span.resolve_span();
+
+        // we want the source_span to capture any whitespace ahead of the diagnostic span to
+        // get the column numbers correct in the DisplayList, and any trailing source code
+        // on the last line for context.
+        let first_line_span = span.file.line_span(region.begin.line);
+        let last_line_span = span.file.line_span(region.end.line);
+        let source_span = span.span.merge(first_line_span).merge(last_line_span);
+        let source = span.file.source_span(source_span);
+
+        // We want to highlight the span, which needs to be relative to source, and in
+        // characters.
+        // Our spans are in terms of bytes, but our resolved spans in terms of characters.
+        let range_start_chars = region.begin.column;
+        let range_len_chars = fast_string::len(span.source_span()).0;
+
+        Slice {
+            source,
+            line_start: 1 + region.begin.line,
+            origin: Some(span.file.filename()),
+            fold: false,
+            annotations: vec![SourceAnnotation {
+                label: "",
+                annotation_type: AnnotationType::Error,
+                range: (range_start_chars, range_start_chars + range_len_chars),
+            }],
+        }
+    }
+
+    let slice = span.map(convert_span_to_slice);
+
+    let snippet = Snippet {
+        title: Some(Annotation {
+            label: Some(annotation_label),
+            id: None,
+            annotation_type: AnnotationType::Error,
+        }),
+        footer: Vec::new(),
+        slices: slice.map(|s| vec![s]).unwrap_or_default(),
+        opt: FormatOptions {
+            color,
+            ..Default::default()
+        },
+    };
+
+    DisplayList::from(snippet)
+}