diff --git a/site/content/docs/04-compile-time.md b/site/content/docs/04-compile-time.md
index 43812426a5a6..4f041c0ff11d 100644
--- a/site/content/docs/04-compile-time.md
+++ b/site/content/docs/04-compile-time.md
@@ -204,12 +204,18 @@ result: {
 			dependencies?: Array<string>
 		}>,
 		script?: (input: { content: string, markup: string, attributes: Record<string, string>, filename: string }) => Promise<{
+			code: string,
+			dependencies?: Array<string>,
+			attributes?: Record<string, string | boolean>
+		}>,
+		expression?: (input: { content: string, markup: string, filename: string }) => Promise<{
 			code: string,
 			dependencies?: Array<string>
 		}>,
 		style?: (input: { content: string, markup: string, attributes: Record<string, string>, filename: string }) => Promise<{
 			code: string,
-			dependencies?: Array<string>
+			dependencies?: Array<string>,
+			attributes?: Record<string, string | boolean>
 		}>
 	}>,
 	options?: {
@@ -224,7 +230,7 @@ The `preprocess` function provides convenient hooks for arbitrarily transforming
 
 The first argument is the component source code. The second is an array of *preprocessors* (or a single preprocessor, if you only have one), where a preprocessor is an object with `markup`, `script` and `style` functions, each of which is optional.
 
-Each `markup`, `script` or `style` function must return an object (or a Promise that resolves to an object) with a `code` property, representing the transformed source code, and an optional array of `dependencies`.
+Each `markup`, `script`, `expression` or `style` function must return an object (or a Promise that resolves to an object) with a `code` property, representing the transformed source code, an optional array of `dependencies`, and an optional object of `attributes`.
 
 The `markup` function receives the entire component source text, along with the component's `filename` if it was specified in the third argument.
 
@@ -254,10 +260,16 @@ const { code } = await svelte.preprocess(source, {
 
 ---
 
-The `script` and `style` functions receive the contents of `<script>` and `<style>` elements respectively (`content`) as well as the entire component source text (`markup`). In addition to `filename`, they get an object of the element's attributes.
+The `script` and `style` functions receive the contents of `<script>` and `<style>` elements respectively (`content`), while the `expression` function receives the contents within the `{...}` expression (`content`).
+
+The `script`, `style`, and `expression` functions receive the entire component source text (`markup`) as well as the name of the file (`filename`).
+
+The `script` and `style` functions also get an object of the element's attributes (`attributes`).
 
 If a `dependencies` array is returned, it will be included in the result object. This is used by packages like [rollup-plugin-svelte](https://github.com/sveltejs/rollup-plugin-svelte) to watch additional files for changes, in the case where your `<style>` tag has an `@import` (for example).
 
+If an `attributes` object is returned, it will replace the attributes on the `<script>` or `<style >` tag.
+
 ```js
 const svelte = require('svelte/compiler');
 const sass = require('node-sass');
diff --git a/src/compiler/preprocess/index.ts b/src/compiler/preprocess/index.ts
index 10771603d76e..a8ea6b15b9ec 100644
--- a/src/compiler/preprocess/index.ts
+++ b/src/compiler/preprocess/index.ts
@@ -2,6 +2,7 @@ import { RawSourceMap, DecodedSourceMap } from '@ampproject/remapping/dist/types
 import { getLocator } from 'locate-character';
 import { MappedCode, SourceLocation, parse_attached_sourcemap, sourcemap_add_offset, combine_sourcemaps } from '../utils/mapped_code';
 import { decode_map } from './decode_sourcemap';
+import { Position } from './quick_parser';
 import { replace_in_code, slice_source } from './replace_in_code';
 import { MarkupPreprocessor, Source, Preprocessor, PreprocessorGroup, Processed } from './types';
 
@@ -89,6 +90,20 @@ function processed_content_to_code(processed: Processed, location: SourceLocatio
 	return MappedCode.from_processed(processed.code, decoded_map);
 }
 
+function stringify_attributes(attributes: Record<string, string | boolean>) {
+	return Object.keys(attributes).map(key => {
+		const value = attributes[key];
+		if (typeof value === 'boolean') {
+			if (value) {
+				return key;
+			}
+		} else {
+			const value_string = value.indexOf('"') > -1 ? `'${value}'` : `"${value}"`;
+			return key + '=' + value_string;
+		}
+	}).filter(Boolean).join(' ');
+}
+
 /**
  * Given the whole tag including content, return a `MappedCode`
  * representing the tag content replaced with `processed`.
@@ -96,7 +111,8 @@ function processed_content_to_code(processed: Processed, location: SourceLocatio
 function processed_tag_to_code(
 	processed: Processed,
 	tag_name: 'style' | 'script',
-	attributes: string,
+	original_attributes: string,
+	updated_attributes: string,
 	source: Source
 ): MappedCode {
 	const { file_basename, get_location } = source;
@@ -104,74 +120,55 @@ function processed_tag_to_code(
 	const build_mapped_code = (code: string, offset: number) =>
 		MappedCode.from_source(slice_source(code, offset, source));
 
-	const tag_open = `<${tag_name}${attributes || ''}>`;
+	const original_tag_open = `<${tag_name}${original_attributes || ''}>`;
+	const updated_tag_open = updated_attributes ? `<${tag_name} ${updated_attributes}>` : original_tag_open;
 	const tag_close = `</${tag_name}>`;
 
-	const tag_open_code = build_mapped_code(tag_open, 0);
-	const tag_close_code = build_mapped_code(tag_close, tag_open.length + source.source.length);
-
-	parse_attached_sourcemap(processed, tag_name);
-
-	const content_code = processed_content_to_code(processed, get_location(tag_open.length), file_basename);
+	const tag_open_code = build_mapped_code(updated_tag_open, 0);
+	const tag_close_code = build_mapped_code(tag_close, original_tag_open.length + source.source.length);
+	const content_code = processed_content_to_code(processed, get_location(original_tag_open.length), file_basename);
 
 	return tag_open_code.concat(content_code).concat(tag_close_code);
 }
 
-function parse_tag_attributes(str: string) {
-	// note: won't work with attribute values containing spaces.
-	return str
-		.split(/\s+/)
-		.filter(Boolean)
-		.reduce((attrs, attr) => {
-			const i = attr.indexOf('=');
-			const [key, value] = i > 0 ? [attr.slice(0, i), attr.slice(i + 1)] : [attr];
-			const [, unquoted] = (value && value.match(/^['"](.*)['"]$/)) || [];
-
-			return { ...attrs, [key]: unquoted ?? value ?? true };
-		}, {});
-}
-
 /**
  * Calculate the updates required to process all instances of the specified tag.
  */
 async function process_tag(
-	tag_name: 'style' | 'script',
+	tag_name: 'style' | 'script' | 'expression',
 	preprocessor: Preprocessor,
 	source: Source
 ): Promise<SourceUpdate> {
 	const { filename, source: markup } = source;
-	const tag_regex =
-		tag_name === 'style'
-			? /<!--[^]*?-->|<style(\s[^]*?)?(?:>([^]*?)<\/style>|\/>)/gi
-			: /<!--[^]*?-->|<script(\s[^]*?)?(?:>([^]*?)<\/script>|\/>)/gi;
-
 	const dependencies: string[] = [];
 
 	async function process_single_tag(
-		tag_with_content: string,
-		attributes = '',
-		content = '',
-		tag_offset: number
+		{ source: content, attributes, raw_attributes, offset, length }: Position
 	): Promise<MappedCode> {
-		const no_change = () => MappedCode.from_source(slice_source(tag_with_content, tag_offset, source));
+		const no_change = () => MappedCode.from_source(slice_source(source.source.slice(offset, offset + length), offset, source));
 
 		if (!attributes && !content) return no_change();
-
 		const processed = await preprocessor({
-			content: content || '',
-			attributes: parse_tag_attributes(attributes || ''),
+			content,
+			attributes,
 			markup,
 			filename
 		});
 
 		if (!processed) return no_change();
 		if (processed.dependencies) dependencies.push(...processed.dependencies);
-		if (!processed.map && processed.code === content) return no_change();
-
-		return processed_tag_to_code(processed, tag_name, attributes, slice_source(content, tag_offset, source));
+		if (!processed.map && processed.code === content && !('attributes' in processed)) return no_change();
+
+		parse_attached_sourcemap(processed, tag_name);
+		if (tag_name === 'expression') {
+			return processed_content_to_code(processed, source.get_location(offset), source.file_basename);
+		} else {
+			const updated_attributes = ('attributes' in processed) ? stringify_attributes(processed.attributes) : null;
+			return processed_tag_to_code(processed, tag_name, raw_attributes, updated_attributes, slice_source(content, offset, source));
+		}
 	}
 
-	const { string, map } = await replace_in_code(tag_regex, process_single_tag, source);
+	const { string, map } = await replace_in_code(tag_name, process_single_tag, source);
 
 	return { string, map, dependencies };
 }
@@ -210,6 +207,7 @@ export default async function preprocess(
 
 	const markup = preprocessors.map(p => p.markup).filter(Boolean);
 	const script = preprocessors.map(p => p.script).filter(Boolean);
+	const expression = preprocessors.map(p => p.expression).filter(Boolean);
 	const style = preprocessors.map(p => p.style).filter(Boolean);
 
 	const result = new PreprocessResult(source, filename);
@@ -225,6 +223,10 @@ export default async function preprocess(
 		result.update_source(await process_tag('script', process, result));
 	}
 
+	for (const process of expression) {
+		result.update_source(await process_tag('expression', process, result));
+	}
+
 	for (const preprocess of style) {
 		result.update_source(await process_tag('style', preprocess, result));
 	}
diff --git a/src/compiler/preprocess/quick_parser.ts b/src/compiler/preprocess/quick_parser.ts
new file mode 100644
index 000000000000..08431287f2b4
--- /dev/null
+++ b/src/compiler/preprocess/quick_parser.ts
@@ -0,0 +1,321 @@
+import { whitespace } from '../utils/patterns';
+
+export interface Position {
+  offset: number;
+  length: number;
+  source: string;
+  attributes: Record<string, string|boolean> | null;
+  raw_attributes: string;
+}
+
+const matching_bracket = {
+  ']': '[',
+  '}': '{',
+  ')': '('
+};
+
+// simplified svelte parser
+export default function parse(template: string) {
+  const scripts: Position[] = [];
+  const styles: Position[] = [];
+  const expressions: Position[] = [];
+
+  let index = 0;
+  while (index < template.length) {
+    if (match('<')) {
+      parse_tag();
+    } else if (match('{')) {
+      parse_mustache();
+    } else {
+      parse_text();
+    }
+  }
+
+  function add_script_expression(get_expression: () => string) {
+    const offset = index;
+    const source = get_expression();
+    expressions.push({ offset, length: source.length, source, attributes: null, raw_attributes: null });
+  }
+
+  function parse_tag() {
+    const tag_start = index;
+    index++;
+    if (eat('!--')) {
+      read_until_regex(/-->/);
+      eat('-->');
+    } else if (eat('/')) {
+      // closing tag
+      read_until('>');
+      index++;
+    } else {
+      const tag_name = read_until_regex(/(\s|\/|>)/);
+      if (tag_name === 'script') {
+        const raw_attributes = read_until_regex(/\/?>/);
+        const attributes = parse_tag_attributes(raw_attributes);
+        let source: string;
+        if (eat('/>')) {
+          source = '';
+        } else {
+          eat('>');
+          source = read_until_regex(/<\/script\s*>/);
+          eat_regex(/<\/script\s*>/);
+        }
+        const length = index - tag_start;
+        scripts.push({ offset: tag_start, length, source, attributes, raw_attributes });
+      } else if (tag_name === 'style') {
+        const raw_attributes = read_until_regex(/\/?>/);
+        const attributes = parse_tag_attributes(raw_attributes);
+        let source: string;
+        if (eat('/>')) {
+          source = '';
+        } else {
+          eat('>');
+          source = read_until_regex(/<\/style\s*>/);
+          eat_regex(/<\/style\s*>/);
+        }
+        const length = index - tag_start;
+        styles.push({ offset: tag_start, length, source, attributes, raw_attributes });
+      } else {
+        while (index < template.length) {
+          allow_whitespace();
+          if (eat('{')) {
+            // handle spread
+            eat_regex(/\s+\.\.\./);
+            add_script_expression(() => read_expression_until('}'));
+            index++;
+            continue;
+          }
+          // attribute name
+          if (!read_until_regex(/[\s=/>"']/)) {
+            break;
+          }
+          allow_whitespace();
+          if (eat('=')) {
+            // attribute value
+            allow_whitespace();
+            const quote_mark = eat("'") ? "'" : eat('"') ? '"' : null;
+            if (quote_mark && eat(quote_mark)) {
+              continue;
+            }
+            const ending_regex =
+              quote_mark === "'"
+                ? /'/
+                : quote_mark === '"' ? /"/ : /(\/>|[\s"'=<>`])/;
+            while (index < template.length) {
+              if (match_regex(ending_regex)) {
+                break;
+              } else if (eat('{')) {
+                add_script_expression(() => read_expression_until('}'));
+                index++;
+              } else {
+                index++;
+              }
+            }
+            if (quote_mark) index++;
+          }
+        }
+      }
+    }
+  }
+
+  function parse_tag_attributes(str: string) {
+    const attributes = {};
+    let i = 0;
+    while (i < str.length) {
+      const char = str[i++];
+      if (/\s/.test(char)) continue;
+      let name = char;
+      while (i < str.length && !/[\s=/>"']/.test(str[i])) {
+        name += str[i++];
+      }
+      if (str[i] === '=') {
+        i++;
+        const quote_mark = str[i];
+        const regex = (
+          quote_mark === "'" ? /'/ :
+            quote_mark === '"' ? /"/ :
+              /(\/>|[\s"'=<>`])/
+        );
+        if (quote_mark === "'" || quote_mark === '"') {
+          i++;
+        }
+        const match = str.slice(i).match(regex);
+        let value;
+        if (match) {
+          value = str.slice(i, i + match.index);
+          i += match.index + 1;
+        } else {
+          value = str.slice(i + 1);
+          i = str.length;
+        }
+        attributes[name] = value;
+      } else {
+        attributes[name] = true;
+      }
+    }
+  
+    return attributes;
+  }
+
+  function parse_mustache() {
+    index++;
+    // {/if}, {/each}, {/await} or {/key}
+    if (eat('/')) {
+      read_until('}');
+      index++;
+    } else if (eat(':else')) {
+      allow_whitespace();
+      if (eat('if')) {
+        allow_whitespace();
+        add_script_expression(() => read_expression_until('}'));
+      }
+      allow_whitespace();
+      eat('}');
+    } else if (match(':then') || match(':catch')) {
+      eat(':then') || eat('catch');
+      if (!eat('}')) {
+        allow_whitespace();
+        read_expression_until('}');
+        eat('}');
+      }
+    } else if (eat('#')) {
+      if (eat('if') || eat('key')) {
+        allow_whitespace();
+        add_script_expression(() => read_expression_until('}'));
+        index++;
+      } else if (eat('each')) {
+        allow_whitespace();
+        add_script_expression(() => read_expression_until(/\sas/));
+        eat_regex(/\sas/);
+        allow_whitespace();
+        read_expression_until('}');
+        index++;
+      } else if (eat('await')) {
+        allow_whitespace();
+        add_script_expression(() => read_expression_until(/\sthen|\scatch|\}/));
+        if (eat_regex(/\sthen/) || eat_regex(/\scatch/)) {
+          read_expression_until('}');
+        }
+        index++;
+      } else {
+        read_until('}');
+        index++;
+      }
+    } else if (eat('@html')) {
+      allow_whitespace();
+      add_script_expression(() => read_expression_until('}'));
+      index++;
+    } else if (eat('@debug')) {
+      allow_whitespace();
+      add_script_expression(() => read_expression_until('}'));
+      index++;
+    } else {
+      add_script_expression(() => read_expression_until('}'));
+      index++;
+    }
+  }
+
+  function parse_text() {
+    while (index < template.length && !match('<') && !match('{')) {
+      index++;
+    }
+  }
+
+  function match(str: string) {
+    return template.slice(index, index + str.length) === str;
+  }
+  function match_regex(pattern: RegExp) {
+    const match = pattern.exec(template.slice(index));
+    if (!match || match.index !== 0) return null;
+    return match[0];
+  }
+  function eat(str: string) {
+    if (match(str)) {
+      index += str.length;
+      return true;
+    }
+    return false;
+  }
+  function eat_regex(pattern: RegExp) {
+    const result = match_regex(pattern);
+    if (result) index += result.length;
+    return result;
+  }
+  function allow_whitespace() {
+    while (index < template.length && whitespace.test(template[index])) {
+      index++;
+    }
+  }
+  function read_until(str: string) {
+    const start = index;
+    const next_index = template.slice(start).indexOf(str);
+    if (next_index > -1) {
+      index += next_index;
+      return template.slice(start, index);
+    }
+    index = template.length;
+    return template.slice(start);
+  }
+  function read_until_regex(pattern: RegExp) {
+    const start = index;
+    const match = pattern.exec(template.slice(index));
+    if (match) {
+      index += match.index;
+      return template.slice(start, index);
+    }
+    index = template.length;
+    return template.slice(start);
+  }
+  function read_expression_until(str: string | RegExp) {
+    const bracket_stack = [];
+    let quote = null;
+    const start = index;
+
+    const is_ending =
+      typeof str === 'string' ? () => match(str) : () => match_regex(str);
+
+    while (index < template.length) {
+      if (bracket_stack.length === 0 && quote === null && is_ending()) {
+        break;
+      }
+      const char = template[index];
+      switch (char) {
+        case "'":
+        case '"':
+        case '`': {
+          if (quote === null) {
+            quote = char;
+          } else if (quote === char) {
+            quote = null;
+          }
+          break;
+        }
+        case '[':
+        case '{':
+        case '(':
+          if (quote === null) {
+            bracket_stack.push(char);
+          }
+          break;
+        case ']':
+        case '}':
+        case ')':
+          if (quote === null) {
+            const find = matching_bracket[char];
+            // assume unclosed bracket
+            while (bracket_stack.length) {
+              if (bracket_stack.pop() === find) {
+                break;
+              }
+            }
+          }
+      }
+
+      index++;
+    }
+
+    return template.slice(start, index);
+  }
+
+  return { scripts, styles, expressions };
+}
diff --git a/src/compiler/preprocess/replace_in_code.ts b/src/compiler/preprocess/replace_in_code.ts
index cf0207afc38b..56adcd70eb47 100644
--- a/src/compiler/preprocess/replace_in_code.ts
+++ b/src/compiler/preprocess/replace_in_code.ts
@@ -1,4 +1,5 @@
 import { MappedCode } from '../utils/mapped_code';
+import parse, { Position } from './quick_parser';
 import { Source } from './types';
 
 interface Replacement {
@@ -21,24 +22,24 @@ export function slice_source(
 }
 
 function calculate_replacements(
-	re: RegExp,
-	get_replacement: (...match: any[]) => Promise<MappedCode>,
+	tag_name: 'script' | 'style' | 'expression',
+	get_replacement: (position: Position) => Promise<MappedCode>,
 	source: string
 ) {
 	const replacements: Array<Promise<Replacement>> = [];
+	const positions = parse(source);
 
-	source.replace(re, (...match) => {
+	(tag_name === 'script' ? positions.scripts : tag_name === 'expression' ? positions.expressions : positions.styles).forEach(position => {
 		replacements.push(
-			get_replacement(...match).then(
+			get_replacement(position).then(
 				replacement => {
-					const matched_string = match[0];
-					const offset = match[match.length - 2];
+					const length = position.length;
+					const offset = position.offset;
 
-					return ({ offset, length: matched_string.length, replacement });
+					return ({ offset, length, replacement });
 				}
 			)
 		);
-		return '';
 	});
 
 	return Promise.all(replacements);
@@ -65,11 +66,11 @@ function perform_replacements(
 }
 
 export async function replace_in_code(
-	regex: RegExp,
-	get_replacement: (...match: any[]) => Promise<MappedCode>,
+	tag_name: 'script' | 'style' | 'expression',
+	get_replacement: (position: Position) => Promise<MappedCode>,
 	location: Source
 ): Promise<MappedCode> {
-	const replacements = await calculate_replacements(regex, get_replacement, location.source);
+	const replacements = await calculate_replacements(tag_name, get_replacement, location.source);
 
 	return perform_replacements(replacements, location);
 }
diff --git a/src/compiler/preprocess/types.ts b/src/compiler/preprocess/types.ts
index 94007371cc35..b3d8b5f8a8c7 100644
--- a/src/compiler/preprocess/types.ts
+++ b/src/compiler/preprocess/types.ts
@@ -11,6 +11,7 @@ export interface Processed {
 	code: string;
 	map?: string | object; // we are opaque with the type here to avoid dependency on the remapping module for our public types.
 	dependencies?: string[];
+	attributes?: Record<string, string | boolean>;
 	toString?: () => string;
 }
 
@@ -35,5 +36,6 @@ export type Preprocessor = (options: {
 export interface PreprocessorGroup {
 	markup?: MarkupPreprocessor;
 	style?: Preprocessor;
+	expression?: Preprocessor;
 	script?: Preprocessor;
 }
diff --git a/src/compiler/utils/mapped_code.ts b/src/compiler/utils/mapped_code.ts
index 58f44d7b8c9f..432d1bbc84f1 100644
--- a/src/compiler/utils/mapped_code.ts
+++ b/src/compiler/utils/mapped_code.ts
@@ -297,9 +297,9 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 }
 
 // parse attached sourcemap in processed.code
-export function parse_attached_sourcemap(processed: Processed, tag_name: 'script' | 'style'): void {
+export function parse_attached_sourcemap(processed: Processed, tag_name: 'script' | 'style' | 'expression'): void {
 	const r_in = '[#@]\\s*sourceMappingURL\\s*=\\s*(\\S*)';
-	const regex = (tag_name == 'script')
+	const regex = (tag_name == 'script' || tag_name == 'expression')
 		? new RegExp('(?://' + r_in + ')|(?:/\\*' + r_in + '\\s*\\*/)$')
 		: new RegExp('/\\*' + r_in + '\\s*\\*/$');
 	function log_warning(message) {
@@ -308,7 +308,7 @@ export function parse_attached_sourcemap(processed: Processed, tag_name: 'script
 		console.warn(`warning: ${message}. processed.code = ${JSON.stringify(code_start)}`);
 	}
 	processed.code = processed.code.replace(regex, (_, match1, match2) => {
-		const map_url = (tag_name == 'script') ? (match1 || match2) : match1;
+		const map_url = (tag_name == 'script' || tag_name == 'expression') ? (match1 || match2) : match1;
 		const map_data = (map_url.match(/data:(?:application|text)\/json;(?:charset[:=]\S+?;)?base64,(\S*)/) || [])[1];
 		if (map_data) {
 			// sourceMappingURL is data URL
diff --git a/test/preprocess/samples/script-in-attribute/_config.js b/test/preprocess/samples/script-in-attribute/_config.js
new file mode 100644
index 000000000000..d5dbe24dc7d3
--- /dev/null
+++ b/test/preprocess/samples/script-in-attribute/_config.js
@@ -0,0 +1,14 @@
+export default {
+	preprocess: {
+		script: () => {
+			return {
+				code: 'tag'
+			};
+		},
+		expression: () => {
+			return {
+				code: 'replaced'
+			};
+		}
+	}
+};
diff --git a/test/preprocess/samples/script-in-attribute/input.svelte b/test/preprocess/samples/script-in-attribute/input.svelte
new file mode 100644
index 000000000000..c658ccdaaf36
--- /dev/null
+++ b/test/preprocess/samples/script-in-attribute/input.svelte
@@ -0,0 +1,43 @@
+<script>
+  let a = 1;
+</script>
+
+<div on:click={() => { return a?.b?.c; }}>
+  this is {a#c}
+</div>
+
+<div
+  use:action={{ foo: 1 }} 
+  use:action="{ foo: 1 }"
+  { ...asdf[123]["qwe(((("]() }
+  class:foo="{123}"
+  transition:fade
+  in:fly={{ y: 10 }}
+/>
+
+{#if a}
+  {#each array['a`[x']["]]]]]]"]['[[[['] as item}
+  {:else}
+    {#await getPromise().[foo()]['"a"'] then { a }}
+    {:catch error}
+    {/await}
+  {/each}
+{:else if b}
+  {#each array[123](f, y, z) as item}
+    { [([(a['asdf](((}}}[][!@#asdf}}}}'])])] + foo }
+  {/each}
+{:else}
+{/if}
+
+{#each foo          as { as }}
+  {as}
+{/each}
+
+<Component
+  a={foo > 32 + { a: 1}}
+  b="3[3+4)4"
+  class="a {b} fds {c[123]} df {{ a: 3 }[`a
+`]} qwe"
+  >
+  <div on:click on:bind> {a} {@debug b} {@html '@debug qwe'} {a < 32 }</div>
+</Component>
\ No newline at end of file
diff --git a/test/preprocess/samples/script-in-attribute/output.svelte b/test/preprocess/samples/script-in-attribute/output.svelte
new file mode 100644
index 000000000000..5b466d5b8280
--- /dev/null
+++ b/test/preprocess/samples/script-in-attribute/output.svelte
@@ -0,0 +1,40 @@
+<script>tag</script>
+
+<div on:click={replaced}>
+  this is {replaced}
+</div>
+
+<div
+  use:action={replaced} 
+  use:action="{replaced}"
+  { ...replaced}
+  class:foo="{replaced}"
+  transition:fade
+  in:fly={replaced}
+/>
+
+{#if replaced}
+  {#each replaced as item}
+  {:else}
+    {#await replaced then { a }}
+    {:catch error}
+    {/await}
+  {/each}
+{:else if replaced}
+  {#each replaced as item}
+    {replaced}
+  {/each}
+{:else}
+{/if}
+
+{#each replaced as { as }}
+  {replaced}
+{/each}
+
+<Component
+  a={replaced}
+  b="3[3+4)4"
+  class="a {replaced} fds {replaced} df {replaced} qwe"
+  >
+  <div on:click on:bind> {replaced} {@debug replaced} {@html replaced} {replaced}</div>
+</Component>
\ No newline at end of file
diff --git a/test/preprocess/samples/script-in-code/_config.js b/test/preprocess/samples/script-in-code/_config.js
new file mode 100644
index 000000000000..c7a085cacce5
--- /dev/null
+++ b/test/preprocess/samples/script-in-code/_config.js
@@ -0,0 +1,9 @@
+export default {
+	preprocess: {
+		script: ({ is_expression, content }) => {
+			return {
+				code: is_expression ? content : 'let z = 42;'
+			};
+		}
+	}
+};
diff --git a/test/preprocess/samples/script-in-code/input.svelte b/test/preprocess/samples/script-in-code/input.svelte
new file mode 100644
index 000000000000..08486ca60da8
--- /dev/null
+++ b/test/preprocess/samples/script-in-code/input.svelte
@@ -0,0 +1,23 @@
+<script>
+  let a = 1;
+</script>
+
+<script context="module">
+  let b = 2;
+</script>
+
+{@html '<script>let c = 3;</script>'}
+
+<script context="worker">
+  let d = 4;
+</script>
+
+{@html `
+  <script>
+    let e = 5;
+  </script>
+`}
+
+<script>
+  let f = 6;
+</script>
diff --git a/test/preprocess/samples/script-in-code/output.svelte b/test/preprocess/samples/script-in-code/output.svelte
new file mode 100644
index 000000000000..bae963fc8e09
--- /dev/null
+++ b/test/preprocess/samples/script-in-code/output.svelte
@@ -0,0 +1,15 @@
+<script>let z = 42;</script>
+
+<script context="module">let z = 42;</script>
+
+{@html '<script>let c = 3;</script>'}
+
+<script context="worker">let z = 42;</script>
+
+{@html `
+  <script>
+    let e = 5;
+  </script>
+`}
+
+<script>let z = 42;</script>
diff --git a/test/preprocess/samples/style-in-code/_config.js b/test/preprocess/samples/style-in-code/_config.js
new file mode 100644
index 000000000000..5af6ff3b386f
--- /dev/null
+++ b/test/preprocess/samples/style-in-code/_config.js
@@ -0,0 +1,9 @@
+export default {
+	preprocess: {
+		style: () => {
+			return {
+				code: 'h1 { color: white; }'
+			};
+		}
+	}
+};
diff --git a/test/preprocess/samples/style-in-code/input.svelte b/test/preprocess/samples/style-in-code/input.svelte
new file mode 100644
index 000000000000..579113ddb976
--- /dev/null
+++ b/test/preprocess/samples/style-in-code/input.svelte
@@ -0,0 +1,45 @@
+<script context="module">
+  let a = '<style>div { color: blue; }</style>';
+  let b = `
+    <style>
+      div { color: green; }
+    </style>
+  `;
+</script>
+
+<style>
+  div {
+    color: purple;
+  }
+</style>
+
+<script>
+  let c = '<style>div { color: blue; }</style>';
+  let d = `
+    <style>
+      div { color: green; }
+    </style>
+  `;
+</script>
+
+{a} {b} {c} {d}
+
+{@html '<style>div { color: yellow; }</style>'}
+
+<style>
+  div {
+    color: purple;
+  }
+</style>
+
+{@html `
+  <style>
+    div { color: pink; } 
+  </style>
+`}
+
+<style>
+  div {
+    color: purple;
+  }
+</style>
diff --git a/test/preprocess/samples/style-in-code/output.svelte b/test/preprocess/samples/style-in-code/output.svelte
new file mode 100644
index 000000000000..91c68d254f37
--- /dev/null
+++ b/test/preprocess/samples/style-in-code/output.svelte
@@ -0,0 +1,33 @@
+<script context="module">
+  let a = '<style>div { color: blue; }</style>';
+  let b = `
+    <style>
+      div { color: green; }
+    </style>
+  `;
+</script>
+
+<style>h1 { color: white; }</style>
+
+<script>
+  let c = '<style>div { color: blue; }</style>';
+  let d = `
+    <style>
+      div { color: green; }
+    </style>
+  `;
+</script>
+
+{a} {b} {c} {d}
+
+{@html '<style>div { color: yellow; }</style>'}
+
+<style>h1 { color: white; }</style>
+
+{@html `
+  <style>
+    div { color: pink; } 
+  </style>
+`}
+
+<style>h1 { color: white; }</style>
diff --git a/test/preprocess/samples/update-attributes/_config.js b/test/preprocess/samples/update-attributes/_config.js
new file mode 100644
index 000000000000..961ac0a03050
--- /dev/null
+++ b/test/preprocess/samples/update-attributes/_config.js
@@ -0,0 +1,16 @@
+export default {
+	preprocess: {
+		script: ({ content, attributes }) => {
+			attributes = { ...attributes, c: false, insert: 'foobar' };
+			delete attributes['lang'];
+			if (attributes.context) {
+				attributes.context = 'module';
+			}
+
+			return {
+				code: content,
+				attributes
+			};
+		}
+	}
+};
diff --git a/test/preprocess/samples/update-attributes/input.svelte b/test/preprocess/samples/update-attributes/input.svelte
new file mode 100644
index 000000000000..19fc081c339a
--- /dev/null
+++ b/test/preprocess/samples/update-attributes/input.svelte
@@ -0,0 +1,14 @@
+<script lang="ts" a="b" />
+
+<script context="worker" foo='a'>
+  let a = 1;
+</script>
+
+<script a="a=3" b='qwe' c d={a} e f class="a {asdf} qwe">
+  let a = 1;
+</script>
+
+<script a="'a' b `c`" b='"a cd `""'>
+</script>
+
+{a}
\ No newline at end of file
diff --git a/test/preprocess/samples/update-attributes/output.svelte b/test/preprocess/samples/update-attributes/output.svelte
new file mode 100644
index 000000000000..c287f096a676
--- /dev/null
+++ b/test/preprocess/samples/update-attributes/output.svelte
@@ -0,0 +1,14 @@
+<script a="b" insert="foobar"></script>
+
+<script context="module" foo="a" insert="foobar">
+  let a = 1;
+</script>
+
+<script a="a=3" b="qwe" d="{a}" e f class="a {asdf} qwe" insert="foobar">
+  let a = 1;
+</script>
+
+<script a="'a' b `c`" b='"a cd `""' insert="foobar">
+</script>
+
+{a}
\ No newline at end of file
diff --git a/test/sourcemaps/samples/attached-sourcemap/_config.js b/test/sourcemaps/samples/attached-sourcemap/_config.js
index 86498caebad3..0af3c492aa6c 100644
--- a/test/sourcemaps/samples/attached-sourcemap/_config.js
+++ b/test/sourcemaps/samples/attached-sourcemap/_config.js
@@ -37,6 +37,9 @@ export default {
 		get_processor('script', 'replace_me_script', 'done_replace_script_1'),
 		get_processor('script', 'done_replace_script_1', 'done_replace_script_2'),
 
+		get_processor('expression', 'replace_me_script', 'done_replace_script_1'),
+		get_processor('expression', 'done_replace_script_1', 'done_replace_script_2'),
+
 		get_processor('style', '.replace_me_style', '.done_replace_style_1'),
 		get_processor('style', '.done_replace_style_1', '.done_replace_style_2')
 
diff --git a/test/sourcemaps/samples/attached-sourcemap/input.svelte b/test/sourcemaps/samples/attached-sourcemap/input.svelte
index 21a47a72a9c9..1ae4405d9e4d 100644
--- a/test/sourcemaps/samples/attached-sourcemap/input.svelte
+++ b/test/sourcemaps/samples/attached-sourcemap/input.svelte
@@ -8,4 +8,4 @@
 		replace_me_script = 'hello'
 	;
 </script>
-<h1 class="done_replace_style_2">{done_replace_script_2}</h1>
+<h1 class="done_replace_style_2">{replace_me_script}</h1>
diff --git a/test/sourcemaps/samples/preprocessed-script/input.svelte b/test/sourcemaps/samples/preprocessed-script/input.svelte
index 11586619e1a0..8b03658265d7 100644
--- a/test/sourcemaps/samples/preprocessed-script/input.svelte
+++ b/test/sourcemaps/samples/preprocessed-script/input.svelte
@@ -6,4 +6,4 @@
 <script>
 	export let foo = { baritone: { baz: 5 } }
 </script>
-<h1>{foo.bar.baz}</h1>
+<h1>{foo.baritone.baz}</h1>
diff --git a/test/sourcemaps/samples/typescript/_config.js b/test/sourcemaps/samples/typescript/_config.js
index c8a955dfbdf4..d0cf8ea4e5bc 100644
--- a/test/sourcemaps/samples/typescript/_config.js
+++ b/test/sourcemaps/samples/typescript/_config.js
@@ -1,5 +1,11 @@
 import * as ts from 'typescript';
 
+const tsCompilerOptions = {
+	target: ts.ScriptTarget.ES2015,
+	module: ts.ModuleKind.ES2015,
+	sourceMap: true
+};
+
 export default {
 	js_map_sources: [
 		'input.svelte'
@@ -9,17 +15,24 @@ export default {
 			script: ({ content, filename }) => {
 				const { outputText, sourceMapText } = ts.transpileModule(content, {
 					fileName: filename,
-					compilerOptions: {
-						target: ts.ScriptTarget.ES2015,
-						module: ts.ModuleKind.ES2015,
-						sourceMap: true
-					}
+					compilerOptions: tsCompilerOptions
 				});
 
 				return {
 					code: outputText,
 					map: sourceMapText
 				};
+			},
+			expression: ({ content, filename }) => {
+				const { outputText, sourceMapText } = ts.transpileModule(content, {
+					fileName: filename,
+					compilerOptions: tsCompilerOptions
+				});
+
+				return {
+					code: outputText.replace(/;([\s]+\/\/# sourceMappingURL=[\S]+)$/, '$1'),
+					map: sourceMapText
+				};
 			}
 		}
 	]
diff --git a/test/sourcemaps/samples/typescript/input.svelte b/test/sourcemaps/samples/typescript/input.svelte
index 93639544b66e..9fd8fa172e17 100644
--- a/test/sourcemaps/samples/typescript/input.svelte
+++ b/test/sourcemaps/samples/typescript/input.svelte
@@ -15,4 +15,4 @@
 </script>
 
 <h1>Hello world!</h1>
-<div>Counter value: {count}</div>
+<div>Counter value: {count as number}</div>