@jridgewell/gen-mapping - npm Package Compare versions

Comparing version 0.2.0 to 0.3.0

dist/gen-mapping.umd.js

@@ -7,2 +7,9 @@ (function (global, factory) {
 
+    const COLUMN = 0;
+    const SOURCES_INDEX = 1;
+    const SOURCE_LINE = 2;
+    const SOURCE_COLUMN = 3;
+    const NAMES_INDEX = 4;
+
+    const NO_NAME = -1;
     /**
@@ -19,2 +26,14 @@ * A low-level API to associate a generated position with an original source position. Line and
     /**
+     * Same as `addSegment`, but will only add the segment if it generates useful information in the
+     * resulting map. This only works correctly if segments are added **in order**, meaning you should
+     * not add a segment with a lower generated line/column than one that came before.
+     */
+    exports.maybeAddSegment = void 0;
+    /**
+     * Same as `addMapping`, but will only add the mapping if it generates useful information in the
+     * resulting map. This only works correctly if mappings are added **in order**, meaning you should
+     * not add a mapping with a lower generated line/column than one that came before.
+     */
+    exports.maybeAddMapping = void 0;
+    /**
      * Adds/removes the content of the source file to the source map.
@@ -42,2 +61,4 @@ */
     exports.allMappings = void 0;
+    // This split declaration is only so that terser can elminiate the static initialization block.
+    let addSegmentInternal;
     /**
@@ -58,22 +79,13 @@ * Provides the state to generate a sourcemap.
         exports.addSegment = (map, genLine, genColumn, source, sourceLine, sourceColumn, name) => {
-            const { _mappings: mappings, _sources: sources, _sourcesContent: sourcesContent, _names: names, } = map;
-            const line = getLine(mappings, genLine);
-            if (!source) {
-                const seg = [genColumn];
-                const index = getColumnIndex(line, genColumn, seg);
-                return insert(line, index, seg);
-            }
-            const sourcesIndex = setArray.put(sources, source);
-            const seg = name
-                ? [genColumn, sourcesIndex, sourceLine, sourceColumn, setArray.put(names, name)]
-                : [genColumn, sourcesIndex, sourceLine, sourceColumn];
-            const index = getColumnIndex(line, genColumn, seg);
-            if (sourcesIndex === sourcesContent.length)
-                sourcesContent[sourcesIndex] = null;
-            insert(line, index, seg);
+            return addSegmentInternal(false, map, genLine, genColumn, source, sourceLine, sourceColumn, name);
         };
+        exports.maybeAddSegment = (map, genLine, genColumn, source, sourceLine, sourceColumn, name) => {
+            return addSegmentInternal(true, map, genLine, genColumn, source, sourceLine, sourceColumn, name);
+        };
         exports.addMapping = (map, mapping) => {
-            const { generated, source, original, name } = mapping;
-            return exports.addSegment(map, generated.line - 1, generated.column, source, original == null ? undefined : original.line - 1, original === null || original === void 0 ? void 0 : original.column, name);
+            return addMappingInternal(false, map, mapping);
         };
+        exports.maybeAddMapping = (map, mapping) => {
+            return addMappingInternal(true, map, mapping);
+        };
         exports.setSourceContent = (map, source, content) => {
@@ -85,5 +97,6 @@ const { _sources: sources, _sourcesContent: sourcesContent } = map;
             const { file, sourceRoot, _mappings: mappings, _sources: sources, _sourcesContent: sourcesContent, _names: names, } = map;
+            removeEmptyFinalLines(mappings);
             return {
                 version: 3,
-                file,
+                file: file || undefined,
                 names: names.array,
@@ -107,3 +120,3 @@ sourceRoot: sourceRoot || undefined,
                     const seg = line[j];
-                    const generated = { line: i + 1, column: seg[0] };
+                    const generated = { line: i + 1, column: seg[COLUMN] };
                     let source = undefined;
@@ -113,6 +126,6 @@ let original = undefined;
                     if (seg.length !== 1) {
-                        source = sources.array[seg[1]];
-                        original = { line: seg[2] + 1, column: seg[3] };
+                        source = sources.array[seg[SOURCES_INDEX]];
+                        original = { line: seg[SOURCE_LINE] + 1, column: seg[SOURCE_COLUMN] };
                         if (seg.length === 5)
-                            name = names.array[seg[4]];
+                            name = names.array[seg[NAMES_INDEX]];
                     }
@@ -133,2 +146,23 @@ out.push({ generated, source, original, name });
         };
+        // Internal helpers
+        addSegmentInternal = (skipable, map, genLine, genColumn, source, sourceLine, sourceColumn, name) => {
+            const { _mappings: mappings, _sources: sources, _sourcesContent: sourcesContent, _names: names, } = map;
+            const line = getLine(mappings, genLine);
+            const index = getColumnIndex(line, genColumn);
+            if (!source) {
+                if (skipable && skipSourceless(line, index))
+                    return;
+                return insert(line, index, [genColumn]);
+            }
+            const sourcesIndex = setArray.put(sources, source);
+            const namesIndex = name ? setArray.put(names, name) : NO_NAME;
+            if (sourcesIndex === sourcesContent.length)
+                sourcesContent[sourcesIndex] = null;
+            if (skipable && skipSource(line, index, sourcesIndex, sourceLine, sourceColumn, namesIndex)) {
+                return;
+            }
+            return insert(line, index, name
+                ? [genColumn, sourcesIndex, sourceLine, sourceColumn, namesIndex]
+                : [genColumn, sourcesIndex, sourceLine, sourceColumn]);
+        };
     })();
@@ -141,42 +175,11 @@ function getLine(mappings, index) {
     }
-    function getColumnIndex(line, column, seg) {
+    function getColumnIndex(line, genColumn) {
         let index = line.length;
-        for (let i = index - 1; i >= 0; i--, index--) {
+        for (let i = index - 1; i >= 0; index = i--) {
             const current = line[i];
-            const col = current[0];
-            if (col > column)
-                continue;
-            if (col < column)
+            if (genColumn >= current[COLUMN])
                 break;
-            const cmp = compare(current, seg);
-            if (cmp === 0)
-                return index;
-            if (cmp < 0)
-                break;
         }
         return index;
     }
-    function compare(a, b) {
-        let cmp = compareNum(a.length, b.length);
-        if (cmp !== 0)
-            return cmp;
-        // We've already checked genColumn
-        if (a.length === 1)
-            return 0;
-        cmp = compareNum(a[1], b[1]);
-        if (cmp !== 0)
-            return cmp;
-        cmp = compareNum(a[2], b[2]);
-        if (cmp !== 0)
-            return cmp;
-        cmp = compareNum(a[3], b[3]);
-        if (cmp !== 0)
-            return cmp;
-        if (a.length === 4)
-            return 0;
-        return compareNum(a[4], b[4]);
-    }
-    function compareNum(a, b) {
-        return a - b;
-    }
     function insert(array, index, value) {
@@ -188,2 +191,12 @@ for (let i = array.length; i > index; i--) {
     }
+    function removeEmptyFinalLines(mappings) {
+        const { length } = mappings;
+        let len = length;
+        for (let i = len - 1; i >= 0; len = i, i--) {
+            if (mappings[i].length > 0)
+                break;
+        }
+        if (len < length)
+            mappings.length = len;
+    }
     function putAll(strarr, array) {
@@ -193,2 +206,36 @@ for (let i = 0; i < array.length; i++)
     }
+    function skipSourceless(line, index) {
+        // The start of a line is already sourceless, so adding a sourceless segment to the beginning
+        // doesn't generate any useful information.
+        if (index === 0)
+            return true;
+        const prev = line[index - 1];
+        // If the previous segment is also sourceless, then adding another sourceless segment doesn't
+        // genrate any new information. Else, this segment will end the source/named segment and point to
+        // a sourceless position, which is useful.
+        return prev.length === 1;
+    }
+    function skipSource(line, index, sourcesIndex, sourceLine, sourceColumn, namesIndex) {
+        // A source/named segment at the start of a line gives position at that genColumn
+        if (index === 0)
+            return false;
+        const prev = line[index - 1];
+        // If the previous segment is sourceless, then we're transitioning to a source.
+        if (prev.length === 1)
+            return false;
+        // If the previous segment maps to the exact same source position, then this segment doesn't
+        // provide any new position information.
+        return (sourcesIndex === prev[SOURCES_INDEX] &&
+            sourceLine === prev[SOURCE_LINE] &&
+            sourceColumn === prev[SOURCE_COLUMN] &&
+            namesIndex === (prev.length === 5 ? prev[NAMES_INDEX] : NO_NAME));
+    }
+    function addMappingInternal(skipable, map, mapping) {
+        const { generated, source, original, name } = mapping;
+        if (!source) {
+            return addSegmentInternal(skipable, map, generated.line - 1, generated.column, null, null, null, null);
+        }
+        const s = source;
+        return addSegmentInternal(skipable, map, generated.line - 1, generated.column, s, original.line - 1, original.column, name);
+    }
 
@@ -195,0 +242,0 @@ exports.GenMapping = GenMapping;

dist/types/gen-mapping.d.ts

@@ -42,2 +42,14 @@ import type { SourceMapInput } from '@jridgewell/trace-mapping';
 /**
+ * Same as `addSegment`, but will only add the segment if it generates useful information in the
+ * resulting map. This only works correctly if segments are added **in order**, meaning you should
+ * not add a segment with a lower generated line/column than one that came before.
+ */
+export declare let maybeAddSegment: typeof addSegment;
+/**
+ * Same as `addMapping`, but will only add the mapping if it generates useful information in the
+ * resulting map. This only works correctly if mappings are added **in order**, meaning you should
+ * not add a mapping with a lower generated line/column than one that came before.
+ */
+export declare let maybeAddMapping: typeof addMapping;
+/**
  * Adds/removes the content of the source file to the source map.
@@ -44,0 +56,0 @@ */

package.json

 {
   "name": "@jridgewell/gen-mapping",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "Generate source maps",
@@ -5,0 +5,0 @@ "keywords": [

README.md

@@ -21,3 +21,3 @@ # @jridgewell/gen-mapping
 ```typescript
-import { GenMapping, addMapping, setSourceContent, encodedMap } from '@jridgewell/gen-mapping';
+import { GenMapping, addMapping, setSourceContent, toEncodedMap, toDecodedMap } from '@jridgewell/gen-mapping';
 
@@ -45,3 +45,3 @@ const map = new GenMapping({
 
-assert.deepEqual(encodedMap(map), {
+assert.deepEqual(toDecodedMap(map), {
   version: 3,
@@ -53,2 +53,14 @@ file: 'output.js',
   sourcesContent: ['function foo() {}'],
+  mappings: [
+    [ [0, 0, 0, 0], [9, 0, 0, 9, 0] ]
+  ],
+});
+
+assert.deepEqual(toEncodedMap(map), {
+  version: 3,
+  file: 'output.js',
+  names: ['foo'],
+  sourceRoot: 'https://example.com/',
+  sources: ['input.js'],
+  sourcesContent: ['function foo() {}'],
   mappings: 'AAAA,SAASA',
@@ -58,2 +70,43 @@ });
 
+### Smaller Sourcemaps
+
+Not everything needs to be added to a sourcemap, and needless markings can cause signficantly
+larger file sizes. `gen-mapping` exposes `maybeAddSegment`/`maybeAddMapping` APIs that will
+intelligently determine if this marking adds useful information. If not, the marking will be
+skipped.
+
+```typescript
+import { maybeAddMapping } from '@jridgewell/gen-mapping';
+
+const map = new GenMapping();
+
+// Adding a sourceless marking at the beginning of a line isn't useful.
+maybeAddMapping(map, {
+  generated: { line: 1, column: 0 },
+});
+
+// Adding a new source marking is useful.
+maybeAddMapping(map, {
+  generated: { line: 1, column: 0 },
+  source: 'input.js',
+  original: { line: 1, column: 0 },
+});
+
+// But adding another marking pointing to the exact same original location isn't, even if the
+// generated column changed.
+maybeAddMapping(map, {
+  generated: { line: 1, column: 9 },
+  source: 'input.js',
+  original: { line: 1, column: 0 },
+});
+
+assert.deepEqual(toEncodedMap(map), {
+  version: 3,
+  names: [],
+  sources: ['input.js'],
+  sourcesContent: [null],
+  mappings: 'AAAA',
+});
+```
+
 ## Benchmarks
@@ -60,0 +113,0 @@

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Improved metrics

Total package byte prevSize

76203

increased by33.47%

Lines of code

592

increased by21.31%

Number of lines in readme file

182

increased by41.09%

No dependency changes